My boat is slow?

[hartland boater]

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I have attached pictures of our 9" hedlund. I set it up over the winter. I was told the following:

You'll run 40-43 all day using the 15 OMC and an aluminum 10" prop. That is what the engine will run with shifter case on a Dawecraft. Get a better stainless prop, and you could see 46-48. Set the cav plate as high as the transom will allow, we run 1.5" over and can't go any higher than that.

Do I not have my cav plate high enough? I had the prop repitched to . I weigh 180 lbs the fastest I could get it to go is 32 mph. any sugestions? do I need to raise the engine higher? I tilted the engine out and the boat just wanted to hop.

any sugestions would be helpfull.

[David Weaver]

[ATTACH]16192[/ATTACH]

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I have attached pictures of our 9" hedlund. I set it up over the winter. I was told the following:

You'll run 40-43 all day using the 15 OMC and an aluminum 10" prop. That is what the engine will run with shifter case on a Dawecraft. Get a better stainless prop, and you could see 46-48. Set the cav plate as high as the transom will allow, we run 1.5" over and can't go any higher than that.

Do I not have my cav plate high enough? I had the prop repitched to . I weigh 180 lbs the fastest I could get it to go is 32 mph. any sugestions? do I need to raise the engine higher? I tilted the engine out and the boat just wanted to hop.

any sugestions would be helpfull.

Must be the pink boat handles!!

[johnsonm50]

If I were told that would do about 32 Id think that to be about right, 40+ seems a bit tall. Your limited by height that it will work w/ a stock prop. These arent surface runners and your gear ratio isnt right for speed. The footprint of the gearcase is also a limiting factor as well as weight. You otherwise have it about where it should be. If you raise it to the point that it cavitates on take off - but you can just get it going and w/ a stainless prop of the right pitch you might get above 35. Dont bother kicking it out beyond where it will smooth out at speed even if you gained a 1/2 mph from it its not worth the wear, tear & risk. You could look for a speed prop to adapt, if your lucky you might find one that works. With any hydro a kill switch is advised, dont wanna pop up to see your boat speeding away

[sam]

32 with a shifter and 180 pounds driver sounds very good to me

I would not believe the other claims with a shifter

[Team B&H]

Call up Ron Hill of Ron Hill Propellers and talk to him about props. He has fooled with stock 15 gearcases and can probably give you plenty of advice. Stock aluminum props are clunky because they are so thick.

[Silas_53A]

Wasnt skoontz seeing the low 40's (42-43?) when testing with the 15 and a stock gear foot? very similar speeds as a J-hydro but without the racing gear foot and no restictor.

[johnsonm50]

Wasnt skoontz seeing the low 40's (42-43?) when testing with the 15 and a stock gear foot? very similar speeds as a J-hydro but without the racing gear foot and no restictor.

From my experience with non race gear feet Id think that possible as well as at the limit. Assuming the motors sound & tuned well, the prop is the trick.
Height is also limited by cooling inlet ports. Running a non thru hub prop on a thru hub is possible, Ive seen it done w/ exhaust relief cut into a Mariner 25, that gained 6 mph with a good SS 2 blade speed prop adapted to it.

[Silas_53A]

maybe he will chime in here, but I am pretty sure he used a stock available prop that fit the 15. This afternoon if I remember I will try and look for his post.

[hartland boater]

Thanks, I had the prop repitched to 9 1/2 X 12. I was told I could get 40 to 45 out of that. It just doesnt go as fast as i thought it would. the motor runs well and I set everything up as many have suggested. finding an exhaust through performance prop do the trick?

[johnsonm50]

Thanks, I had the prop repitched to 9 1/2 X 12. I was told I could get 40 to 45 out of that. It just doesnt go as fast as i thought it would. the motor runs well and I set everything up as many have suggested. finding an exhaust through performance prop do the trick?

It could make a good difference but B4 spending alot of cash on an overpitched prop that might slow ya down more, it would be a good idea to get a Tiny Tach & know what your actual RPM & speed are.. As well as the known pitch of the prop your running. Sometimes less pitch will be faster & more powerful while more can cause your motor to not be able to get over the hump & plane off. Orrr its a guess . Good Luck. Mike

[Ron Hill]

Shorten Housing

Thanks B and H for the recommendation for props, but right now, I'm too busy with "STUFF" and my "BUCKET LIST" keeps growing...

http://www.boatracingfacts.com/forum...8617#post68617

Shortening the housing, using a nose cone is on my "Bucket List"...

Chad ran "A" Hydro last Sunday at Copperopolis, over his dead 210 pound body....(It was my Father's Day request...) With our new DAWE HYDRO, Tammy's number two wheel Chad could go 48.7 MPH ..second heat...First heat with my wheel, Chad went 49.7 mph)...Of course there were 7-8 boats and Chad was last...Next year, I'll ask for something different on Father's Day!!!

Point being, a "PRODUCTION GEARCASE" was a lower water pickup, big diameter prop could be made to go at least this fast with a 200 pounder...

KT Schwab ran 48 or so with a stock prop....but at J weight...

I'd jack the mother up another inch and beat the prop over the trailer hitch ball and add as much cup and you can get....IF you feel the motor isn't getting enough water, plug the top water pick up holes with something that won't blow out or suck in...Like Marine Tex...

Good luck, you got a cool boat..enjoy!

[Hydroglobe17J]

Maybe the engine timing can be raised?

[WildBill5-A]

Your speed is not unreasonable to expect from the stock engine, gearcase and slightly reworked prop. Your problem is running out of rpm with the stock gearcase & prop. I put an old stock 18 omc on a c runabout and it ran 34 mph but was pegged at 6300 rpm....the omc rpm was limited by reed float, not power or prop or weight. Tells me you need a significantly higher pitched prop, stainless, and better gear ratio, if you want to run in the 40's. Note that the mini grand prix boats running 25 hp stock foot engines on small tunnel hulls with 15 or 17 pitch props are running in the mid 40's. I wouldn't expect your 15 to do that well in the stock form. Suggest you look into a gear foot if you really want to go that fast. Here's a nomograph that works pretty well with stock engines/props (not as accurate with racing hulls/engines). 10 percent slip works good for heavy boats and stock gearfeet, 5 percent for light boats and stock gearfeet, and not much of anything for racing hulls/gearfoots. Just a rough estimate for judging if you are in the ballpark or not.

[johnsonm50]

As stated above, a race foot would go. They are made to fit a 15 as a bolt on, [not sure about the driveshaft]. Speed cost $$ - how fast ya wanna go?? 'A' boats at the races are pretty fast running a version of the OMC 15.

[Skoontz]

Yes, 41-43MPH using a Dawecraft hydro, stock 15 OMC engine, and no gag collar. 10" aluminum prop, engine set with prop shaft 3.5" under the bottom.

We did similar things using the Merc 15, 40-43.

Far as the 2 hole looper doing over 32, loose the aluminum prop, run a pretty heavy cup 3 blade, and jack the motor to the lowest hole on the gear case or install a transom water pick up. We hit 52 with a 50 on a GW Invader boat, boat years ago, but the master built my props, Don Henrich.