To wedge or not?

[Pit_o_Money]

Question: I have a 21ft Kachina with a 460 BBF w/ Torker2 manifold and Edelbrock 750 carb. Berk JG without divertor. I am running 55MPH at about 4300RPM. Will a wedge give me less wetted area or will it be a waste of time? I plan on getting a Place Divertor but the funds aren't there for the boat.

[HBjet]

There are many other steps you should make before adding wedge to your pump. If you don't have a Place Diverter, I would suggest getting one. The will help you get more of the boat free'd up. IF your still not happy, you could get a cut back shoe, and ride plate combo. With these, you should be able to free up the boat for more mph and still maintain a smooth ride (no porpoise) I would also look into what impeller you have, and find out what RPM makes the most power for your motor. IF your impeller it too big, you could have it turned down (example, AA to and A)
Without knowing the condition of the pump, proper impeller, condition of the motor and hull, I would say 55mph is about right for a 21ft boat.
HBjet

[Pit_o_Money]

HB, Your right about the Diverter, that is the plan but just not yet. I am not new to boating, just new to making performance mods. So another question is how do I tell what impeller I have. I know about the tag but the pump has a GS marine sticker on it and I don't know what has been done to it. As far as condition of the hull, it is pretty straight(no hook) from what I can tell. The motor has 230 hours on it. Runs strong, and smooth. The only issue is the oil pressure dips down when warm. I have had the boat for 2 seasons and not had any probs. Now I would like to go a little faster. So I was just wondering if a wedge would help out even just a tiny bit in the mean time until I can get a diverter. Thanks
DJ

[HBjet]

POM, I don't know if GS Marine records the serial numbers of the boat, pump, or CF numbers when you do business with them. I would first call GS and see if Greg can recall the pump mods by some sort of identification marking. After that, you might want to ask what he thinks the next step should be, since they probably did the last pump work to the boat. If you added some wedge (1 or 2 degrees) I really don't think you would see a perfromance gain unless it was open, flat water. Having the wedge and no place diverter will cause the nose of the boat to lift much higher when getting on plane and take longer. If you don't have some sort of trimming (tabs) the boat may also porpoise. At slower speeds, the nose will also stick higher in the air. I know they cost less, but they are mainly used when fine tunning the pump to the boat, after the cut back shoe, ride plate, etc. Don't let me stop you from doing what you want to do, but I just don't think you will be happy with the end results. I would suggest a Place Diverter so you can trim down for getting on plane quicker and less bow rise, and then trimming up for better top end, and getting the boat free'd up. Lets also not forget, the Rooster Tail. Good Luck!
HBjet
[This message has been edited by HBjet (edited May 09, 2002).]

[Pit_o_Money]

HBjet, Thanks!! I really want to do a diverter. So I was just wondering what was up with the wedge. I will try calling Greg to see. Thanks for the input.
I assume HB stands for Huntington? If so were not too far. And from the pics I have seen posted, the work you are doing on yours looks sweet!
DJ
[This message has been edited by Pit_o_Money (edited May 09, 2002).]

[hack job]

Originally posted by HBjet:
POM, I don't know if GS Marine records the serial numbers of the boat, pump, or CF numbers when you do business with them. I would first call GS and see if Greg can recall the pump mods by some sort of identification marking. After that, you might want to ask what he thinks the next step should be, since they probably did the last pump work to the boat. If you added some wedge (1 or 2 degrees) I really don't think you would see a perfromance gain unless it was open, flat water. Having the wedge and no place diverter will cause the nose of the boat to lift much higher when getting on plane and take longer. If you don't have some sort of trimming (tabs) the boat may also porpoise. At slower speeds, the nose will also stick higher in the air. I know they cost less, but they are mainly used when fine tunning the pump to the boat, after the cut back shoe, ride plate, etc. Don't let me stop you from doing what you want to do, but I just don't think you will be happy with the end results. I would suggest a Place Diverter so you can trim down for getting on plane quicker and less bow rise, and then trimming up for better top end, and getting the boat free'd up. Lets also not forget, the Rooster Tail. Good Luck!
HBjet
[This message has been edited by HBjet (edited May 09, 2002).]
now this is were iam going to disagree with you hb, not too be dick but on our 21 carribean we added a 8 deg wedge and it did free up some weted surface for 12 bucks you cant beat the mph increse we got two mph out of it and the boat rode nicer. good luck!
Tyson www.plumbersassracing.com (http://www.plumbersassracing.com)

[Pit_o_Money]

@
[This message has been edited by Pit_o_Money (edited May 09, 2002).]

[Aluminum Squirt]

I have a wedge question. I'm running a 15' aluminum jet boat with a Legend and SBC. I do have a place diverter and I love it. On GPS my fastest speeds are not all the way trimmed out. I'm getting an extra MPH or two my sticking the pump back in the water a couple of degrees after I've trimmed up all the way. This leads me to believe that I do not need a wedge because more 'up' is hurting my top end. Is this sound reasoning or is there something else going on here that I am not seeing? Also, I want to go to a manual setup instead of hydraulic. When I switch, am I going to lose any of my up/down adjustment? I've got a little to give but if its more than a degree or two, then I may have to add a small wedge to get all of my angle back. What do you guys think?-Aluminum Squirt

[HBjet]

Aluminum Squirt, Going from hydrolic to manual still gives you the same amount of movement, just the manual has set positions of trim, where as the hydrolic give you a lot more freedom of where you want the trim angle to be at.
POM, I do live in Huntington Beach and thanks! Right now the boat is at the interior shop, should get it back in 2 weeks?
Hack Job, 8 degrees huh? WOW, that is a lot of wedge, I thought 4 degrees was big. Did you take two 4 degree wedges and put them together? I would think that would be way too much. I mean, it would probably get great lift, but what about getting on plane, or pulling a skier? How has that been doing for you guys on that boat?
HBjet
[This message has been edited by HBjet (edited May 09, 2002).]

[Aluminum Squirt]

HBJet-I've looked at both systems and that's what I thought but there was a thread a while back on the other board and somebody mentioned the possibility that you may get a little more travel out of the hydraulic set up. My max speed isn't at max trim so even if I did loose a tiny bit, it would only affect the size of my roost when I'm cruising. Thanx for the feedback. Is my reasoning sound for my thoughts on not needing a wedge? Right now, it loosens up just fine and my max speed is slightly under max trim-Aluminum Squirt

[canuck1]

Alum Squirt
My ride is similar to yours and with 3 degrees it runs mid 70's. with 4 degrees it slows down approx. 7 mph but the tail is like 300'

[Licketty Split]

For what its worth, Its like this,
Think of the direction the water is being forced out of the jet nozzle, draw a line through the centerline of it... this (for the most part) your line of thrust.
OK so were does lift come from if we are trusting down? If you find the center of gravity and calculate were your moment of inertia and drag forces follow that line until the two meet this is a point of leverage that picks the bout out of the water. One of the more notable effects is pitch; witch gives air entrapment hulls their lift. This Pitch effect works off the center of water lift as a fulcrum between the CG and the nozzle thrust moment (not line) Think of putting a pipe in the nozzle and standing on it...that is the moment.
Bottom line. (Finally) You trade thrust for lift. So if we move the nozzle back we have just created a longer pipe and we do not have to work as hard for same pitch gains and the center of water lift has less weight being exerted on it (i.e. less boat in the water). Along with ease of the leverage forces comes a more efficient line of thrust for the given result in lift and MORE SPEED.
In regard to AS post you most likly have an entrapment hull (or close to one) and once you develop aero lift you’re waiting the energy by shoving the ass end further in the water.
These are all trade off's what works on one boat may not work on another, you get too long a pump and you loose to much in internal friction (as well as having to cut a hole in the back of your garage) these theories are for you to experiment with the limit is your imagination (or $$$$ as in my case)
Good luck Hope to see you in Havasu on Memoreal day http://www.planetsmilies.com/smilies/cool/cool10.gif

[hack job]

Originally posted by HBjet:
Aluminum Squirt, Going from hydrolic to manual still gives you the same amount of movement, just the manual has set positions of trim, where as the hydrolic give you a lot more freedom of where you want the trim angle to be at.
POM, I do live in Huntington Beach and thanks! Right now the boat is at the interior shop, should get it back in 2 weeks?
Hack Job, 8 degrees huh? WOW, that is a lot of wedge, I thought 4 degrees was big. Did you take two 4 degree wedges and put them together? I would think that would be way too much. I mean, it would probably get great lift, but what about getting on plane, or pulling a skier? How has that been doing for you guys on that boat?
HBjet
[This message has been edited by HBjet (edited May 09, 2002).]
hb
getting on plane was fine and pulling a skier was fine. the 8 deg was one we got form jack and it was one piecs made of plasticbut it was fine . any how it was a great way to gain some speed i odnt know if it will work on all boat as well, butworked good in this application. though we do not have that boat any more it was my dads and i drove it, i couldnt hang with that rep http://free.***boat.net/ubb/wink.gif
j/k RD later
Tyson www.plumbersassracing.com (http://www.plumbersassracing.com)