V-drive setup

[Mandella69]

Need some help in figuring out the performance of my boat. Some specifics:
Boat is a 1969 Mandella short deck hull. Motor is a 460 Ford with 525 Hp at 5900rpm (dyno). V-drive is a 12* Casale with 25% gears. Prop is a 11 1/2 X 15 SS Stellings. Ignition is MSD with a 6000rpm limiter chip. Tach is AutoMeter. Some folks have told me the gears are too high and the motor will never pull them, but that is what is there for now. I want to keep the motor at 6000rpm max.
I did some runs this weekend with a GPS and came up with the following numbers. 3000rpm = 37.5mph. 3500rpm = 43mph. 4000rpm = 49mph. 5800rpm = 74.5mph. In all cases the prop slip is about 28%. This seems very high.
To be truthful, boat felt much faster but hard to judge on water. Other boaters said it was running really well but the numbers do not agree. I would appreciate any comments.

[dmontzsta]

I would try a few props, your slip is right around 30% +/-.

[lilrick]

Are you satisfied with the performance? What are you trying to achieve? Boat speed?

[Mandella69]

The boat is a lake boat. I bought it as a piece of junk other than the hull was sound. I have restored the hull and built a moderate HP motor. I am aiming for a 85mph boat. So no, I am not satisfied with the performance so far. The boat has incredible acceleration and is a blast to drive but comes up short in the top end. The prop, a two blade by the way, came with boat, so I have not tried any other ones.
It could be difficult to find other props to try around here. So I guess my questions relate to if a different prop was the answer, is there enough HP to reach my goals or am I dreaming. And what would be a better prop? I would probably have to buy a new prop and try it. So I can not afford to many "mistakes".

[lilrick]

I wouldn't BUY a prop right now. Try to borrow a couple different sizes and see what the boat wants. It may like the prop you have . You have to give a little to get a little. The prop you have now works good all around and has good acceleration. If you try a smaller prop, you may lose acceleration and gain top end as an example. Try a few other props and record your info like you did with your current prop . Good luck.

[lilrick]

Just another thought...If your motor pulls that gear with that prop to 6000 rpm, and you want to go faster, try a prop with more pitch. Since you don't want to spin the motor over 6k and thats where your revlimiter is set, I would load the motor until it can only spin 6k.

[058]

Need some help in figuring out the performance of my boat. Some specifics:
Boat is a 1969 Mandella short deck hull. Motor is a 460 Ford with 525 Hp at 5900rpm (dyno). V-drive is a 12* Casale with 25% gears. Prop is a 11 1/2 X 15 SS Stellings. Ignition is MSD with a 6000rpm limiter chip. Tach is AutoMeter. Some folks have told me the gears are too high and the motor will never pull them, but that is what is there for now. I want to keep the motor at 6000rpm max.
I did some runs this weekend with a GPS and came up with the following numbers. 3000rpm = 37.5mph. 3500rpm = 43mph. 4000rpm = 49mph. 5800rpm = 74.5mph. In all cases the prop slip is about 28%. This seems very high.
To be truthful, boat felt much faster but hard to judge on water. Other boaters said it was running really well but the numbers do not agree. I would appreciate any comments.
Why limit the rpm to 6K?

[dmontzsta]

Why limit the rpm to 6K?
yeah, I just read this over and the motor makes peak power at 5900? I would bump the limiter up to 6500 (depending on if the internals are good). I still think your answer for more speed lies in the prop.

[Rattle Can Lou]

Why limit the rpm to 6K?
It's a fricken Ford!!!!!!!!!!!!!!!
5500 max.

[dmontzsta]

It's a fricken Ford!!!!!!!!!!!!!!!
5500 max.
True, you dont need to spin the piss out of them to make power, they make good power from the low end on up...good point RCL, you are a smart guy. :)

[058]

It's a fricken Ford!!!!!!!!!!!!!!!
5500 max.What happens at 5500?

[HM]

I had very similar slip % numbers on my Mandella. I tried all sorts of props, but usually got 28 - 30% slip. I had the bottom blue printed, but never ran it with the new bottom, and never heard if the number went down. Frankly, I was more concered with trying to get my boat to take a set over slip numbers as no matter what I did, my Mandella liked to skip like a silver dollar in the Patomic. I did hear that 800+ HP and a big block cured the skipping/porpoising issue. I had been running a blown sbc with about 750 HP, 7200 redline and 25 gears. It topped out at 98 with a 12 x 16 two blade.
These Mandellas run really wet and really heavy and I think that i why the high slip #'s. The bottoms of these boats were not considered fast...if they were, then more people would have copied them. Mandellas biggest asset is they are basically bullet proof in the rough stuff.
If you want to run 85 MPH with a max of 5900 RPM, you will need 48 gears with a 15 inch pitch prop and 36 gears with a 16 pitch prop(with 30% slip). And obviously, a lot more HP to pull those gears....and that would be so your boat tops out at 85. That is just the straight math.
There are a few other Mandella owners on here...I am sure they have some numbers for comparison.

[superdave013]

I would say that a big heavy boat that's way over geared and running 74 mph is pretty good. Think about it, in 1969 74mph was pretty frickin fast for a lake boat.
The only way to go faster is to spin the prop faster. With 25's you need more power. Droping the gear down to 18's will wake it right up. I say drop 'em down to 12 ~ 15's but I already know you won't be down for the rpm.

[dmontzsta]

I would say that a big heavy boat that's way over geared and running 74 mph is pretty good. Think about it, in 1969 74mph was pretty frickin fast for a lake boat.
The only way to go faster is to spin the prop faster. With 25's you need more power. Droping the gear down to 18's will wake it right up. I say drop 'em down to 12 ~ 15's but I already know you won't be down for the rpm.
I agree Dave.
My old Lavey ran 72mph with a mild 390 Ford. To be honest, I was scared. Scared to dump more money in it "in hopes" that it would carry the nose better or scared of going faster while porpoising out of control. So I sold it and bought a boat that I know people have made go fast. :)

[HM]

I agree Dave.
My old Lavey ran 72mph with a mild 390 Ford. To be honest, I was scared. Scared to dump more money in it "in hopes" that it would carry the nose better or scared of going faster while porpoising out of control. So I sold it and bought a boat that I know people have made go fast. :)
So you graduated to permenant trailer queen?
Wait wait wait....I wanna hear how fast it is GOING to be again. I just can't get enough of that. It takes a close second to my drunk uncle telling me about his 100 mph jet boat with a panther pump and 327 Chevy. :devil: :devil: :devil: :D :D :D

[lilrick]

So you graduated to permenant trailer queen?
Wait wait wait....I wanna hear how fast it is GOING to be again. I just can't get enough of that. It takes a close second to my drunk uncle telling me about his 100 mph jet boat with a panther pump and 327 Chevy. :devil: :devil: :devil: :D :D :D
ewh weee...ouch!!! Don I must second Franks opinion........YOU ARE A BIATCH!:D

[dmontzsta]

ewh weee...ouch!!! Don I must second Franks opinion........YOU ARE A BIATCH!:D
Frank doesn't even have a boat. :D

[lilrick]

you're right....He doesn't have "A" boat....He has 5!

[Mandella69]

I thank everyone for their comments. I have also read the other thread regarding Mandellas with interest. If I have read things right, the Mandella hull is certainly not the best for high speeds but 85 is certainly possible with the right set up. 30% slip is not abnormal for this boat. To answer a couple of questions, I chose 6000rpm purely on spec, not anticipating such high prop slip. Motor is strong enough to take 6500rpm when power falls off quickly. The crank might be the weak link as it is an offset ground stock crank. Motor was built before all the new stuff for 460's. Everything else is top notch.
It has been suggested that only way to go faster is to spin prop faster or increase the pitch. This will require more power. Not sure what replacing the 25 gears with 18 would do as you would have to rev motor to 6400 to achieve same level of performance as at present. Unless I have missed something or do not understand.
At this point I am assessing what I should be doing. Leave the boat as is and enjoy, add some more power or move on to a different hull that will be more amenable to higher performance. I just hate to abandon a boat I have spent a lot of $$$ and time on.
Thanks again.

[dmontzsta]

you're right....He doesn't have "A" boat....He has 5!
oh, so now you are trying to recruit him to your gay swinger lifestyle? :jawdrop:

[lilrick]

oh, so now you are trying to recruit him to your gay swinger lifestyle? :jawdrop:
thread jacker...Mr. mandella, please ignore my gay friend Don....Carry on with your questions...

[dmontzsta]

thread jacker...Mr. mandella, please ignore my gay friend Don....Carry on with your questions...
I will drag this thread straight to bench racers, if you dont STOP now! :D

[HM]

I thank everyone for their comments. I have also read the other thread regarding Mandellas with interest. If I have read things right, the Mandella hull is certainly not the best for high speeds but 85 is certainly possible with the right set up. 30% slip is not abnormal for this boat. To answer a couple of questions, I chose 6000rpm purely on spec, not anticipating such high prop slip. Motor is strong enough to take 6500rpm when power falls off quickly. The crank might be the weak link as it is an offset ground stock crank. Motor was built before all the new stuff for 460's. Everything else is top notch.
It has been suggested that only way to go faster is to spin prop faster or increase the pitch. This will require more power. Not sure what replacing the 25 gears with 18 would do as you would have to rev motor to 6400 to achieve same level of performance as at present. Unless I have missed something or do not understand.
At this point I am assessing what I should be doing. Leave the boat as is and enjoy, add some more power or move on to a different hull that will be more amenable to higher performance. I just hate to abandon a boat I have spent a lot of $$$ and time on.
Thanks again.
I had a blast running my boat in the 80-85 MPH range. The reason SuperDave reccomended lower gears is that bigger gears is a trap many v-drivers fall into attempting to get higher top end numbers while simultaneously loosing the snappy acceleration. For example, you will lose about 4 MPH on the top end by going from 25 gears to 18 gears (with the same redline) but....the acceleration difference is huge. Most of the fun in these boats is not just running at top speed, but how quickly you get there is a big part. Since they are recreational boats and we want them to last a long time, if you are going to flat foot the thing for anything over 10 seconds, you should probably have one had on the bible (as Jim Wilkes likes to say).
I don't know anything about Fords, so I have comment on that.
I spent a LOT of money trying to make my Mandella go fast. I think your 85 MPH goal is pretty reasonable but you will want spin more RPM to get there so you don't give up your acceleration by using bigger gears.
I also got to a point where I was done trying to make old boats go faster than they should. As SuperDave said 73 was very very fast for these boats back in the day. I was told these Mandellas were made when what they needed to win a marathon race was go 70 MPH without breaking.

[HM]

Hey Donald and Ricky...
I started a new thread for Q-ball in the proper forum: I am gonna be so fast.... (http://www.***boat.com/forums/showthread.php?p=2640142#post2640142)
:D

[LeE ss13]

I have never really liked the phrase "slip" or "slippage". I prefer the term "Efficient" or "Efficiency", like the prop and gear choice were %80 efficient. I don't think the prop is "slipping", or it would be cavitating. It is producing a certain amount of thrust in the water and the total sum of drag from the boat is working against it. Mandella69's boat is only %70 efficient by the numbers. I would not look so much on gear and prop changes, but what kind of changes can make this boat more free in the water? First thing I would is ask where is the cavitation plate at top speed. If it is not level or up a little, then make changes to the setup so that it is. Are the springs strong enough to hold the plate up at speeds. 75 mph on a Mandella is about where the plate gets sucked back down and will limit the speed to that. I know, because I owned a Mandella for several years and had a lot of fun with it. Ideally, you should shoot for %80 which would be 84 mph at 5900. That is probably a good rpm for stock heads. You need a set of TFS heads or other after market ones to turn them 7K. And even with that, most 460s are cast iron crankshafts. My $.02

[lilrick]

I have never really liked the phrase "slip" or "slippage". I prefer the term "Efficient" or "Efficiency", like the prop and gear choice were %80 efficient. I don't think the prop is "slipping", or it would be cavitating. It is producing a certain amount of thrust in the water and the total sum of drag from the boat is working against it. Mandella69's boat is only %70 efficient by the numbers. I would not look so much on gear and prop changes, but what kind of changes can make this boat more free in the water? First thing I would is ask where is the cavitation plate at top speed. If it is not level or up a little, then make changes to the setup so that it is. Are the springs strong enough to hold the plate up at speeds. 75 mph on a Mandella is about where the plate gets sucked back down and will limit the speed to that. I know, because I owned a Mandella for several years and had a lot of fun with it. Ideally, you should shoot for %80 which would be 84 mph at 5900. That is probably a good rpm for stock heads. You need a set of TFS heads or other after market ones to turn them 7K. And even with that, most 460s are cast iron crankshafts. My $.02
Good point.

[058]

I thank everyone for their comments. I have also read the other thread regarding Mandellas with interest. If I have read things right, the Mandella hull is certainly not the best for high speeds but 85 is certainly possible with the right set up. 30% slip is not abnormal for this boat. To answer a couple of questions, I chose 6000rpm purely on spec, not anticipating such high prop slip. Motor is strong enough to take 6500rpm when power falls off quickly. The crank might be the weak link as it is an offset ground stock crank. Motor was built before all the new stuff for 460's. Everything else is top notch.
It has been suggested that only way to go faster is to spin prop faster or increase the pitch. This will require more power. Not sure what replacing the 25 gears with 18 would do as you would have to rev motor to 6400 to achieve same level of performance as at present. Unless I have missed something or do not understand.
At this point I am assessing what I should be doing. Leave the boat as is and enjoy, add some more power or move on to a different hull that will be more amenable to higher performance. I just hate to abandon a boat I have spent a lot of $$$ and time on.
Thanks again.
The 460 cranks are not the weak link, the stock rods are. Use a light piston and a decent aftermarket rod and the short block is good to 7500+ providing the clearances are set up for that. Make sure it has a good supply of oil [10 qts or more] and a good pump. The 460 2 bolt block is ok to use up to 750- 800 HP, some have pressed it more but tune ups are very criticle. Check out what some of the truck pullers are doing with 460 Fords, studded 2 bolt blocks, cast cranks and turning 8500-9K for 25-30 seconds at a time. You say you have an offset ground crank, what is the stroke and what rods/pistons do you have?

[LD Mandella]

I tend to agree with les, where is the cav plate set at WOT and how is the boat riding? i.e. where is the water breaking on the hull. Mandellas run pretty loose at higher speeds sorta dancing on the tail which is not always the most comfortable feeling but that is where they get efficient. Check the cav plate set-up as described by Les and run the boat up as loose ( plate up ) as possible and let us know how things change. One other question, how much gas and other crap are you hauling around? Finally 25s are pretty big but if your motor will carry the nose you will get in the 80s.

[LeE ss13]

The 460 cranks are not the weak link, the stock rods are. Use a light piston and a decent aftermarket rod and the short block is good to 7500+ providing the clearances are set up for that. Make sure it has a good supply of oil [10 qts or more] and a good pump. The 460 2 bolt block is ok to use up to 750- 800 HP, some have pressed it more but tune ups are very criticle. Check out what some of the truck pullers are doing with 460 Fords, studded 2 bolt blocks, cast cranks and turning 8500-9K for 25-30 seconds at a time. You say you have an offset ground crank, what is the stroke and what rods/pistons do you have?
I stand corrected. You are right. Back when we built a 460, I think Pro Stock cars were using cast cranks and doing well. We would buzz it 7K with a 22 gear. Later I had heard it kicked a rod out, (stock ones), but I had lost touch with the owner. As I remember, the exhaust ports on the stock heads were the limiting factor. We had some TFS heads with Ross pistons to match. Sounded great.