# looking for more performance 40hp outboard



## GuppyII (Sep 14, 2008)

If you put on a hydrofoil and gain speed your motor is not set up properly. Its too low. Trim your motors cavitation plate level with the hull, the cav plate should be above the bottom by 1/2-1 inches, the foil should be out if the water thus adding no benefit other than planing. Of course an aluminum prop will blow out set up like this, if you don't have stainless you will not see any performance out of your motor. Aluminum is only for spares! 
Good luck
Oh and just because a dealer set up your boat doesn't mean it is set up correctly. The just slap a motor on and know that 95% of the people which are buying a boat have no clue about performance! They can sell more hydrofoils that way....lol...


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## brookie1 (Jan 26, 2011)

That motor (1991 40 horse johnson) has a top rpm range of 5500 and a gear ratio of 2.42. So a 13 pitch prop will give you a maximum speed of 28mph independent of everything else unless you overrev the motor. This is not a screamer and probably won't be unless you figure out how to add 20 or 30 horsepower to the motor. You can put a 15 or 17 pitch prop on it but all that will do is lower the max rpms the motor will run unless like I said, it is severely overreving now. My 16 foot aluminum with a 75 merc 2-stroke and a laser II 20 pitch stainless does 41, ok but not exactly speedy. The gear ratio is 2.33. This is after trying a couple different props to get near max rpm for the motor.


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## mi duckdown (Jul 1, 2006)

The ventplate @ wot will be out of the the water @WOT
How a Hydrafoil will Gain speed???. 
IF all the boat manufactures thought it was a good idea. would they not put them on all motors.???


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## tracker14 (Jun 1, 2007)

The cav. plate is about level with the bottom of the hull. on plane there is only about 24" of boat in the water. The fish finder says 34mph but it seems faster I didn't have gps with me last weekend. It has a used 11.75x 17p prop on it right now, it is aluminum and shows wear. (Prop Wizard) comes up with a :SS 12.25x17 for top speed and performance. Would that cup water better with the bigger dia.? Hole shot is fine. I have a mini tach ordered, but with hunting season here this project might get set back.

I agree if foils added speed every boat would have one.


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## mi duckdown (Jul 1, 2006)

SO. you are going to spend lots of money to get 5 mph.
it ain't happening.......
Ok lets go Back. you do not know your actuall rpm's and GPS speed?


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