Mr Havasu Cat prop slip calcs

[SVO 540]

Mr. Havasu Cat, I hope you don't mind me trying to help make your DCB run better slip numbers. I have been giving your stats a lot of thought. I have compared it to the data from my boat and also to the research I have done on other Mach 26's tested in the mags.
This is what I believe your facts are. You ran 105mph @ 5800rpm with a 1.50gear and 32pitch prop. Good performance, but sloppy out of the hole. Boat was loaded with fuel and had passangers. By my calc, this gives you a slip of 10%. Then to improve the out of the hole performance, you tried a 1.35 gear. This netted 104mph @ 5800rpm with 1.35gear and 30pitch prop. Boat was loaded with fuel and had passangers. You didn't say if this improved out of the hole performance. Again, by my calc, this gives you a slip of 15%.
Here are my comments and observations. First, going from a 1.50 to a 1.35 is the same as increasing your prop pitch by 3 sizes. Therefore, a 1.50 with a 32 pitch is roughly the same as a 1.35 with a 29 pitch. You ended up with a 1.35 with a 30 pitch, making this combo taller than your previous 1.50 setup. You went to a taller setup yet you were able to pull the same 5800rpm. Where did you get the extra HP to pull the taller gearing to 5800? My guess is you may have had the boat trimmed out too far, making the slip % go up and allowing your motor to turn the taller setup to 5800rpm. In other words, your motor didn't make any more power, but the trim setting allowed in to pull the taller gear to 5800rpm.
Why do you have more slip with the taller gear. The answer is you should not. According to Fred Inman of Imco, a 28pitch prop is the ideal size and generates the least amount of slip. You are closer to this ideal prop size with your current setup than you were with your 1.50/32 setup. If this statement by Fred is true, you should produce less slip with your 1.35/30 setup.
You should be able to repeat the 10% slip pass you made with your 1.50/32 setup. I calculate a top speed of 110mph @ 5800rpm with a 1.35/30 setup using 10% slip.
February 1999 Hot Boat magazine. In this issue (I think you can get a copy of this article from this web site) they test a Mach 26 with a blown 509. This boat ran 111mph at 5600rpm with a 1.36 gear and a 30 inch prop cupped to 32 inches and lab finished. For my calculation of this slip, I assumed a 31pitch because I didn't know how to treat the prop mods. This eguals a slip of 8%. (I JUST GOT AN IDEA, WOULDN'T IT BE GREAT IF HOT BOAT WOULD PROVIDE THE SLIP % ON THE BOATS THEY TEST)
To get the low slip % you need the right water conditions and load or lack of load in the boat. If not, you may be trimming the boat to compensate for these factors, putting the drive in a less that ideal position for top speed. Get the ice chest, anchor and passangers out.
Here is my prediction, First, Your X dimention is in the right spot. At Havasu, with the right air and water conditions, the correct trim setting, a very light load in your boat and your current 1.35/30 setup, you will run at 8% slip netting a top speed of 114mph at 5800rpm.
Like I said in another posting, I am happy to compare my info to that of yours.
SVO 540 - Out.

[RiverDave2]

That just got technical like... http://free.***boat.net/ubb/biggrin.gif
RD

[gimprvr]

SVO 540: I have a question for you regarding Prop sizing: I just took delivery of a 26 ft cat. I have 502 with a vortech supercharger putting out approximately 575HP. I recently ran the boat and achecived the following 74.5 MPH on the GPS, I had the drive trimmed all the way down and was hitting the revlimiter at 5300. I was running a 28 ptch Bravo four blade. I know she has plenty more to give but somwhere the numbers just don't add up. I'm confident the speed ws accurate because of the GPS. Can you please make a prop suggestion for my next test and let me know what you think my numbers will reflect based upon your sugesstion? Thanks in advance

[boatnam2]

damm gimprivr,something dont right

[MrHavasuCat]

SVO540,
I definitely think you are right regarding the slip numbers. I think the boat with less weight and better conditions would run faster, and yes the boat is much better out of the hole now with the new gears and smaller prop. I think the cooler air temp this past weekend helped with a little more hp and let me pull the 30" prop to 5800.
I actually know the guy who owns the boat you are talking about from the ***boat test. That boat is running a standard (non xr) drive. I think the xr takes more hp to turn than the standard bravo from people I have talked to that have switched drives and lost speed. I am going to try a 28 inch prop this summer in the heat and see if I see better numbers. The 30 in the heat of the summer is just to much prop unless I decide to add some boost. Thanks for the help.

[mrpumps HTM]

Originally posted by MrHavasuCat:
SVO540,
I definitely think you are right regarding the slip numbers. I think the boat with less weight and better conditions would run faster, and yes the boat is much better out of the hole now with the new gears and smaller prop. I think the cooler air temp this past weekend helped with a little more hp and let me pull the 30" prop to 5800.
I actually know the guy who owns the boat you are talking about from the ***boat test. That boat is running a standard (non xr) drive. I think the xr takes more hp to turn than the standard bravo from people I have talked to that have switched drives and lost speed. I am going to try a 28 inch prop this summer in the heat and see if I see better numbers. The 30 in the heat of the summer is just to much prop unless I decide to add some boost. Thanks for the help.
MR HC your choice of a 28 prop is good but you might want to try a non lab it hooks up better out of the hole, the xr takes about 10hp more than standard drive but i think a good 28lab/10 lbs boost maybe1/2 tanks of gas and it will work just fine

[SVO 540]

Originally posted by gimprvr:
SVO 540: I have a question for you regarding Prop sizing: I just took delivery of a 26 ft cat. I have 502 with a vortech supercharger putting out approximately 575HP. I recently ran the boat and achecived the following 74.5 MPH on the GPS, I had the drive trimmed all the way down and was hitting the revlimiter at 5300. I was running a 28 ptch Bravo four blade. I know she has plenty more to give but somwhere the numbers just don't add up. I'm confident the speed ws accurate because of the GPS. Can you please make a prop suggestion for my next test and let me know what you think my numbers will reflect based upon your sugesstion? Thanks in advance
No problem. What is your drive gear ratio. I would guess 1.50 based on the info but it is better to confirm. Also, what max RPM to you want to run a wide open throttle. You need to stay off the rev limiter to get max speed. With that, I can guess at it for ya.

[riverliver]

SVO450
Man you must have cleard out all the beers in the brain, way to much thinking goin on.
oh by the way left message on your work voice mail, Trent is to funny!!!!!!!!

[SVO 540]

Mr Havasu Cat, I found in the testing that I have done that a non-lab prop has less slip through the mid range and has more slip on the top end when compared to a lab prop. This is consistant with what mrpumpshtm said. For family boating at Havasu, I prefer to run a non-lab 28, but for the big top end numbers, I run a lab 30.
The info you gave me still doesn't add up. If you assume that the additional RPM dicussed in the opening post is due to better air, then why did your slip go from 10% to 15% with your prop and gear change? If the drive trim was the same in both passes, the only answer is additional weight in the boat.
I have found that my mach finds an overdrive gear and really gets aired out when there is no extra weight in the boat. Also, when I am running light and really flying, my trim is between 0 and +1. Add more weight and I have found that I need to add more positive trim and muscle the boat. It doesn't get that overdrive gear sensation when there is a full load in the boat.
Make your speed runs with a light load and you may find this overdrive gear sensation. I would be happy to take you for a ride in my boat so you can get a feel of what I am talking about. Your hull is the same as mine so I am sure it's there.
I hope you don't mind my comments, but I have one more. I am concerned that you will turn to many RPM with the 28pitch prop. You are currently turning your 30pitch 5800rpm. Remove two cup sizes and you might pick up 300 to 400rpm. If so, this puts your rpm at 6100 to 6200. If you have a solid roller cam, this is ok, but my guess is it is hyd. Talk to your engine builder about max rpm and desired rpm at full throttle.
As you can tell, I love this shit and would be happy to help with your testing and also let you try my props, etc.

[Duck]

About gimprvr's post-you say you had the drive all the way down. That's a rpm/mph killer to me. Was there any up trim performed? Should be in the 85-90 range.

[MrHavasuCat]

Mrpumps,
I am running 9 pounds of boost at 5800 rpm. Blosdale says the motor is good to about 15 pounds so I might bump it up just a little.
SVO540,
I know what you are talking about with the "overdrive" feeling. When I ran the bigger numbers with the 1.50's and the 32 I was very light on fuel (towards the end of the day)and you can definitely feel the difference. I had a mach 26 last year with outboards and it had a much different feeling. You could air the boat out a lot more and get a very "light" feeling out of the boat. This is similar to how my current boat feels when it is light. I am sure this is the same feeling you are describing. I always end up putting to much fuel in the boat because I am running av gas and don't fill up at the marina, therefor I don't want to get stuck on the water with not enough gas. I had to be towed once with my last boat when I ran out of gas and it kind of sticks in my head. As far as rpm goes, I am running a Crane hydraulic roller cam with Jesel valve train. Jeff Blosdale says the motor can spin up to 6200 rpm, but he would like to see it kept under 5800.
I am going to use the smaller prop in the summer, and I will also try it in the cooler weather with less trim and see how it runs. I think the excessive positive trim I am running might be a reason for some of my slip numbers. After having an outboard boat it is hard not to want to trim the shit out of the motors. The outboards loved a lot of trim. Thanks for the reply.
[This message has been edited by MrHavasuCat (edited December 05, 2001).]

[SVO 540]

Mr. Havasu Cat,
My guess is that you will end up with the same prop selection as me. That is, a non-lab 28 for lake cruising and a lab 30 for the top speed runs.
Here is an interesting stat from my mach. At 3000rpm using a non-lab 28, my speed is around 55mph and my boost is -1. At 3000rpm using my lab 30, my speed is around 50mph and boost is +1. The non-lab 28 is much better in this cruising speed range. It is 5mph faster and makes 2psi less boost. Less boost because there is less load on the motor with a smaller prop and more mph because the non-lab has less slip than a lab in the mid range. I have run 112mph with my non-lab 28 (had to lift because of rpm limitations) and 132mph with my lab 30 and I can honestly say that I like the non-lab 28 better, except for getting the big mph number. By the way, with my non-lab 28 I can over rev the motor at WOT which is my concern for you with a 28.
Mr. Pumps, Three questions:
1. Do you have any interesting slip data from your HTM you can share?
2. What props do you use and for what purpose?
3. What is your trim setting at cruising, drag racing and top speed runs?

[gimprvr]

SVO 540 : A 1.5 ratio is correct. I am also running a Max Machine Worx Lower unit with nose cone. As afar as the MAX RPM, make a recomendation. I am anly running 4-lbs of boost.
Duck, I was running it all the way down because with the drive trimmed up I would run out of RPM quicker.

[SVO 540]

Gimprvr, The answer is .... 32pitch lab.
Ok, so how did I get to that prop. I assumed the following: You are looking for top speed only, this prop could be sloppy out of the hole. The desired engine rpm is 5000.
I don't know what kind of boat you have, but I know that a 25 Daytona with a HP500 (470 prop shaft HP), 1.50 gear and 28 pitch prop will run low 80's at around 5000 rpm. Using this as a benchmark for your boat gives you 100 more HP with the same 1.50 gear.
The next statement is somewhat of a guess but I think every 1 inch increase in prop pitch will decrease wide open throttle (WOT) rpm by 200. Also, a lab finished prop will turn 150 more rpm at WOT than a non-lab prop. Although this will be different depending on gear ratio, 1.50, 1.36, 1.25 etc.
Going from your 28 to a 32 will decrease WOT rpm by 800. I think this will be too much of a reduction. This is why I suggested the lab finished 32, because you will pick up about 150 rpm, also it is faster. Therefore going from a non-lab 28 to a lab 32, I would guess that you will decrease your engine rpm by 650.
I am not suggesting decreasing your engine rpm from 5300, but decreasing it from what it would have turned had it not had the rev limiter and putting it in the 5000rpm range.
What if I am correct? Here are your stats. 5000rpm, 1.50gear, 32pitch prop, 10% slip factor gives you a top speed of 91 mph.
I hope you like it. If any other readers have comments or disagree please post. Keep in mind, this is only a best guess estimate.

[gimprvr]

Thanks SVO, you seem to have a thorough wealth of knowledge and I really appreciate your willingnes to share. I had planned on trying a 32. It just seems so big for this application. Do you see any way to hit the 95mph or even the elusive 100! I have a brand new imco 1 inch shortened gearcase as a back up. what do you think this will provide?

[SVO 540]

Gimprvr, Before I do any more speculation, tell me what kind of boat you have and if it is open or closed bow. I also need more info on your motor...as much detail here as possible. More info on drive, standoff box, yes or no, etc. Have you tried the 1 inch shorter IMCO lower? The more detail you can give me the better I can guess at it. With this info, we can work backwards from 100mph to see what it will take to get you there.

[kab]

I like that SVO 540 work backwards from 100. I have a DCB Mach 26 open bow 502/ whipple charger not broke in it yet,but when it is I'll be postin some info on it to see what I need to reach 90.

[riverliver]

SVO540
would it not be better to run a 1.35 and try to get to the magic 28 prop then a 32 with a 1.50, I think the chance of grenadeing that 1.50 with a 32 are very high.
I think we need to change your name to mister SLIP. LOL
nice talking with you on the phone today, tell Bug and the little one Hi.

[mrpumps HTM]

Originally posted by SVO 540:
Gimprvr, Before I do any more speculation, tell me what kind of boat you have and if it is open or closed bow. I also need more info on your motor...as much detail here as possible. More info on drive, standoff box, yes or no, etc. Have you tried the 1 inch shorter IMCO lower? The more detail you can give me the better I can guess at it. With this info, we can work backwards from 100mph to see what it will take to get you there.
SVO540... could you calculate my slip on this iam curious about it 1.5 gear 32 prop/7000 rpm

[FastCats]

Hi SVO,
I would like to commend you on your observations and calculations on most of the boards boats and set ups. Very informative and quite accurate. Do you ever take into consideration, water conditions, water temp, current, wind, etc. I know I do.
I have currently been testing with a 1:30 gear, 36 labs, at 6000rpm, average 9% slip, and am finding that the conditions mentioned above do come into play along with the obvious.
Again, good work with the "blue oval", I find that part interesting.
Scott
[This message has been edited by FastCats (edited December 05, 2001).]

[SVO 540]

Mrpumps, There are 5 variables that go into this calculation, MPH, RPM, prop pitch, gear ratio and silp. If you know four of these you can solve for the fifth. Generally, slip is the unknown variable that is calculated. In your post you only gave me three variables, you did not give mph. I did three calc anyway making a speed assumption. If your speed is 127 slip is 10%, speed is 130 slip is 8%, speed is 134 slip is 5%. If you give me actual mph I can recalc, my guess is you are somewhere in my assumed mph numbers.
In an earlier post I asked you three questions. I would be thankful if you could answer these for me.

[SVO 540]

Originally posted by riverliver:
SVO540
would it not be better to run a 1.35 and try to get to the magic 28 prop then a 32 with a 1.50, I think the chance of grenadeing that 1.50 with a 32 are very high.
I think we need to change your name to mister SLIP. LOL
nice talking with you on the phone today, tell Bug and the little one Hi.
Riverliver, I was thinking about that recommendation and that may turn out to be a good combo for Gimprvr. Let me explain why I suggested what I did. As indicated in an earlier post, a 1.50 gear and 32 pitch prop is almost the same as a 1.36 gear and a 28 pitch prop.
Everything seem cool right. Here is the monkey wrench. As you know from your 25 Daytona, it takes alot more engine torque to turn the taller 1.36 gear. This is why an HP500 powered 25 Daytona will run 5 mph faster with a 1.50 gear and 28 pitch prop vs a 1.36 gear and 25 pitch prop. Torque is not a problem with a roots type blower, there is tons of it. Torque can be a problem with naturally aspirated motors like the HP500. I made the assumption that the torque produced from Gimprvr's vortech supercharged motor would be more similar to an HP500 motor than to a roots supercharged type motor. Gimprvr gave me very little information to make a recommendation.
Hope to see you soon Riverliver.

[mrpumps HTM]

Originally posted by SVO 540:
Mrpumps, There are 5 variables that go into this calculation, MPH, RPM, prop pitch, gear ratio and silp. If you know four of these you can solve for the fifth. Generally, slip is the unknown variable that is calculated. In your post you only gave me three variables, you did not give mph. I did three calc anyway making a speed assumption. If your speed is 127 slip is 10%, speed is 130 slip is 8%, speed is 134 slip is 5%. If you give me actual mph I can recalc, my guess is you are somewhere in my assumed mph numbers.
In an earlier post I asked you three questions. I would be thankful if you could answer these for me.
SVO540 The reason i asked about slip i had a formula that would not work my mph was 132 @7000 RPM W/32PROP AND 1.5 GEARS . props i run are a bit different ,cuped ,1/2 pitch. for 1/4mile 28 works well 7100ish at the lights with 1.5 gears at about 118mph,on the lake its a 30/32 lab prop.My trim guage is a manual indicator might be different but in the 1/4 mile i fly the nose to about 5/6 about 100mph then drop the trim to 3 over 100mph and let her go. next season ill get about 500 or 600 rpm and a few more hp from the engine ,gear change we will shoot for the record ha ha maybe ??? THANKS
[This message has been edited by mrpumps HTM (edited December 05, 2001).]

[SVO 540]

Mrpumps, With that info, I calc your actual slip to be 6.6%. That is a great slip number. Everything is working well on your set up. What trim settings do run cruising, racing and top speed?

[SVO 540]

Mrpumps, I see you answered my trim question, sorry for asking twice. Does a trim setting of 5 mean +5 or is it +2. What I mean by the latter is typically the notches go -2, -1, 0, +1, +2, +3 etc. So five notches could be +2.

[mrpumps HTM]

Originally posted by SVO 540:
Mrpumps, I see you answered my trim question, sorry for asking twice. Does a trim setting of 5 mean +5 or is it +2. What I mean by the latter is typically the notches go -2, -1, 0, +1, +2, +3 etc. So five notches could be +2.
SVO540 .............5+

[Tom Slick]

SVO, what's up man. Been riding lately? If you have a second, can you figure out my slip? 107 MPH, 6300 RPM, 30 lab, 1.50 gear.

[gimprvr]

SVO 540: I have not tried the Imco unit yet, I intend to sometime in late Jan. I am running a Rayson Craft 26 with Open bow. I have a 502MAG EFI motor with the Vortech Running 4LBS. The motor puts out 575hp on the dyno. Based upon the numbers I gave at 74.5mph, 5300rpm and a 28 prop doesn't this indicate a problem somwhere? with these numbers doesn't this put my slip @ over 20%? Was this all the information you need to get me to the century mark?

[MrHavasuCat]

Tom Slick,
You are running about 10% slip with those numbers. 10% puts you at 107.4 mph, so you are very close to 10%.

[Tom Slick]

Thanks MrHavasuCat. Is 10% good, bad, ok? What kind of boat do you have?

[MrHavasuCat]

10% is good to very good depending on what type of boat you have. I have a DCB Mach 26.

[SVO 540]

Originally posted by mrpumps HTM:
[QUOTE]
next season ill get about 500 or 600 rpm and a few more hp from the engine ,gear change we will shoot for the record ha ha maybe ??? THANKS
[This message has been edited by mrpumps HTM (edited December 05, 2001).]
Mrpump, I calculated that another 600 RPM should get you 11 MPH, based on your slip, 32 pitch prop and a 1.50 gear. SHOOT FOR THE RECORD!!!!

[SVO 540]

[QUOTE]Originally posted by Tom Slick:
[B]SVO, what's up man. Been riding lately? If you have a second, can you figure out my slip? 107 MPH, 6300 RPM, 30 lab, 1.50 gear.
Mr. Havasu Cat is right, your slip is 10%. I think the reason your slip is 10% and mrpumps is 6.6% is top speed. You both have the same boat, but the faster you go, the less wetted surface, thus less slip.
I have done the last two Over the hill gang mx races. I try to ride once a week but it doesn't always happen. I have a list of buddies who I call when I go riding, do you want to be on that list?

[SVO 540]

[QUOTE]Originally posted by FastCats:
Do you ever take into consideration, water conditions, water temp, current, wind, etc. I know I do.
Scott, I do take this into consideration but it is more of a mental note. It is for these conditions that I try to do all my testing in the same day but even then conditions change. We have more variables to worry about that Austin Coil.
"I have currently been testing with a 1:30 gear, 36 labs, at 6000rpm, average 9% slip"
Scott, tell me about your boat. You mention "labs". Does this mean you have twins? It would be interesting to compare slip on a single vs. twin engine cat.

[SVO 540]

Originally posted by gimprvr:
SVO 540: I have not tried the Imco unit yet, I intend to sometime in late Jan. I am running a Rayson Craft 26 with Open bow. I have a 502MAG EFI motor with the Vortech Running 4LBS. The motor puts out 575hp on the dyno. Based upon the numbers I gave at 74.5mph, 5300rpm and a 28 prop doesn't this indicate a problem somwhere? with these numbers doesn't this put my slip @ over 20%? Was this all the information you need to get me to the century mark?
20.47% to be exact. Don't worry, this is not a good measure of your slip. This is because you had it trimmed all the way down to stay of the rev limiter. Also, bouncing off the rev limiter could also be a factor.
There are a few combos that will get you to 100MPH. Assuming you keep your 1.5 gearing this is what has to happen. Remember, we are going to back into 100MPH, therefore we will make some assumptions and solve for the necessary engine rpm. With a 32 pitch prop, 1.5 gear, 10% slip factor and 100 MPH, the needed engine rpm is 5495. This is a problem because it is beyond your current 5300 rev limit. Something on the motor would need to be changed but that may be your best solution to hit that rpm. Hell, mrpumps turns his motor north of 7000. I don't want to give engine advice as I don't know much about the 502 MAG EFI, keep in mind I am a Ford guy.
I don't think I would recommend this approach but if your engine requires you to stay below 5300, you need either a biger prop or bigger gears. If you ran a 34 pitch prop, 1.50 gear, 10% slip and 100mph the needed engine rpm is 5171. Like Riverliver suggested, you could go with a 1.36 gear. This would be a 30 pitch prop, 10% slip and 100mph needing 5314rpm.
I really like the 1.50 gear and 32 pitch prop combo for your boat. I would try to make this work by allowing your motor to spin more rpms. My advise would be to go out and try that 32 pitch prop with your 1.50 gear in that 1 inch shorter IMCO lower. Get some good data. Record speed at different engine rpms. 3000, 3500, 4000, 4500, 5000 and WOT. Write this down on a piece of paper. Record water and air conditions. You will need all this data when you start making changes to your setup. After you do this post your results and we can go from there.
SVO 540 - OUT

[mrpumps HTM]

Originally posted by SVO 540:
Mrpump, I calculated that another 600 RPM should get you 11 MPH, based on your slip, 32 pitch prop and a 1.50 gear. SHOOT FOR THE RECORD!!!!
SVO540 LOOK WHAT YOU STARTED! YOU ARE NOW (MR SLIP) ....calculate 1.24 gear,30 or 32 prop at 6800 TO 7200 RPM i think i have to pick up some brass BALLS...................140ISH THANKS AGAIN

[mrpumps HTM]

Originally posted by SVO 540:
Mrpump, I calculated that another 600 RPM should get you 11 MPH, based on your slip, 32 pitch prop and a 1.50 gear. SHOOT FOR THE RECORD!!!!
SVO540 LOOK WHAT YOU STARTED! YOU ARE NOW (MR SLIP) ....calculate 1.24 gear,30 or 32 prop at 6800 TO 7200 RPM i think i have to pick up some brass BALLS...................140ISH THANKS AGAIN

[mrpumps HTM]

Originally posted by Tom Slick:
SVO, what's up man. Been riding lately? If you have a second, can you figure out my slip? 107 MPH, 6300 RPM, 30 lab, 1.50 gear.
WHATS UP TOM SLICK what now no more summer,they say this weekend 80ish i dont know castaic not looking to bad

[SVO 540]

Originally posted by mrpumps HTM:
SVO540 LOOK WHAT YOU STARTED! YOU ARE NOW (MR SLIP) ....calculate 1.24 gear,30 or 32 prop at 6800 TO 7200 RPM i think i have to pick up some brass BALLS...................140ISH THANKS AGAIN
mrpumps HTM,
Are you sitting down for this. This is fricken insane. Here it is. 7000 rpm, 1.24 gear, 30 pitch and 6% slip = 150.8 mph. But wait, it gets better. The same 7000 rpm with a 32 pitch prop = 160.8 mph.
Forget about that HTM drag class stuff, your now ready to take on the IHBA Competition Eliminatior class. This is getting fun.
Now the question is how much slip will there be in those BRASS BALLS?
Mr. Slip - OUT

[RiverDave2]

Did Mr.Pump say Castaic this weekend? On saturday or sunday? I was thinking of going up there with a buddy of mine.. If we can hook up for that ride then I'll definately make it a point to be there! http://free.***boat.net/ubb/smile.gif
RD

[riverliver]

MR. Slip (svo540)
what do you think the slip difference is on the Daytona from the 1.50 to 1.36, you know the numbers that we talk about.
P.S. don't account for the El diablo,Tic Tac's or the Green thumb. LOL

[mrpumps HTM]

Originally posted by RiverDave2:
Did Mr.Pump say Castaic this weekend? On saturday or sunday? I was thinking of going up there with a buddy of mine.. If we can hook up for that ride then I'll definately make it a point to be there! http://free.***boat.net/ubb/smile.gif
RD
RIVERDAVE IS THAT YOU ??????????????????????? maybe sunday because the snow is calling (saturday) BUT ITS ON IF WE HOOK UP!!!!!!!!
[This message has been edited by mrpumps HTM (edited December 06, 2001).]

[kmahtm]

OOPS

[Tom Slick]

Pumps, whats up? My sled is up at Havasu, so Castaic is out this weekend! Are you guys going to head up to Havasu again any time soon? I need to get up there at some point to bring the boat back, so I can pump it up for next season.

[RiverDave2]

Mrpump, I think Sunday is calling for shitty weather.. The weather for Saturday is going to be right around 80 degrees! If your going to be out on Sunday I might just drive up there bymyself though.
Got an Extra Lifeline? http://free.***boat.net/ubb/wink.gif
RD

[mrpumps HTM]

Originally posted by RiverDave2:
Mrpump, I think Sunday is calling for shitty weather.. The weather for Saturday is going to be right around 80 degrees! If your going to be out on Sunday I might just drive up there bymyself though.
Got an Extra Lifeline? http://free.***boat.net/ubb/wink.gif
RD
RD ......HELL i dont know maybe saturday looks like no snowboarding for me this sat

[MIKEHTMSR24]

East coast here, in Greenville,SC.
I have a 1999 HTM SR-24 with a N/A 540, I had my motor dynoed the last time I did some work to it.
683 hp @ 5700 and they stopped @ that rpm because of the hyd. roller cam
676 torque @ 4600. This should put my prop shaft hp around 650.
I am currently running a labbed 26 Bravo 1. Bronson Hill did the lab work. RPM is around 5300 to 5500 (depending on conditions). Avg. speed is around 85 and best GPS speed was 89.7 @ 5500 (light load and good chop).
I have a 1.36 drive ratio with a Imco 2" shortie. I picked up about 3.5 when I went with the shortie. I also did a back to back test with a stock 26 Bravo 1 and the Bronson Hill and I picked up 2.5 mph without any rpm gain.
My question is:
Do you think I will pick up any speed if I switch to a 1.5 gear ratio and change prop pitch to get it at the same rpm I am turning my 26?
This will not be a real cheap change over. It would be nice to know if it would really help out b-4 the cash goes out the door.
My motor has a lot of torque but not like a blower motor does. http://www.geocities.com/mickey1692000/Memhtml/MikeParks.html
[This message has been edited by MIKEHTMSR24 (edited December 17, 2001).]

[MrHavasuCat]

I say no because the smaller prop will give you less slip than the larger wheel you would have to run with the 1.50's. You will also have a harder time planning with the larger prop, and this might even be increased with the 2" shorter drive. my.02

[SVO 540]

I have to agree with MrHavasuCat. I don't think the dollars would be well spent. You could gain more speed by spending those bucks somewhere else. There is one point of conflict and that is you are N/A and these motors generally like the 1.50 gears, however you have alot of torque (676) and I think this is enough to power that 1.36 gear with good results.

[MIKEHTMSR24]

Bam Marine in FL is claiming (not to me) but in general that the 1.5s are faster. Their reasoning behind this is that the motor doesn't have to turn the prop as much in the water. I did have one of my buddies tell me it picked up mph on one of his buddies boat. It picked up 4.5 more mph. What I don't know is what motor the boat had in it.
I agree what you are saying about take off with the larger pitches.
I would like to have a little more rpm than what I am getting out of the 26 in the summer. months. So maybe a 28 would be ok with the 1.5.
I might get to try my buddies outdrive on my boat next summer. He has a 1.5 with a shortie. This would be a cheap test. If I can do this it's a no brainer. If I can't it could be very expensive and my wallet is not that fat. If If If trying my buddies drive works then maybe I could find someone who would want to swap. I like gaining speed w/o adding hp like my shortie and labbed prop did for me. Both gave me 6 more mph.
The web site for Bam Marine I think is www.go-fast.com (http://www.go-fast.com)
You might have to do a search for it. They have a really cool site to determine slip, hp, weight, or rpm.

[MIKEHTMSR24]

I forgot to tell you that Bam Marine gives his explanation on the advantage of the 1.5 gear ratio. I think it is on something like performance tips???????