Do I need prop work?

[crkdltr]

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[crazymanme2]

Are there any gains, that are of benefit to my setup, in having the prop worked on? I've heard cupping may help in taking off and turning but will sacrifice speed and wot RPM.

Cupping a prop is like adding a pitch which means you'll lose about 250 rpm's.A cup will let you run your motor higher on the transom with less slip.

 

[Howard]

The motor is a short shaft sitting on a 20" transom so the cavitation plate is parallel to the bottom of the boat

Please correct me if I am wrong but isn't a short shaft motor 15". A 20" transom requires a long shaft motor which has a 20" shaft. I just went through this also.

 

[crkdltr]

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[KRS62]

Is there any stat you are unhappy with? I have no idea what they charge to "work a prop" but have you considered looking for a used (and different) one? Perhaps you can go higher in pitch and gain a little speed?

KRS

 

[crazymanme2]

I can tell you that the transom is 20" and the cavitation plate is parallel or just slightly lower than the bottom of the boat when the motor is tilted down.

If this is the case than you have a long shaft motor.(20")

 

[crkdltr]

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[rgpemt]

I have a mod V, with decent chines along the length of the hull. I do notice the steering issue at higher speeds, but added one of the "whale tail" cavitation plate wings.

That seems to have helped a bunch, I can cut a donut...well almost. I still get the skipping sensation if i'm going all out (16 foot with a 70) but it does handle better with the wings.

Pitch is usually the answer to more speed. I have gone as far as 21 inches of pitch on other boats with really amazing results. What you gain on the top end, you will loose on the other, another option to think about is a 4 bladed prop...it will give you great hole shot, top end will drop a tad, but you will have much more bite in the water.

My two cents

Bob

 

[RBuffordTJ]

I wish my flat bottom turned as sharp as a V but they usually don't. Some people like putting a whale tale (hydrofoil) on them for faster lift out of the hole and some stability, but you would get more stability in turns from trim tabs. Stainless props don't flex like aluminum do but in your application I wouldn't stress using either one, the racers like them because they don't flex and give like aluminum will so they get a little more boost from them. The down side is when you bang a SS prop it can cause damage in the gearcase where an aluminum will take the damage and 'ding' up .

Porposing is caused by a hook in the hull, usually near the back from improper trailering. Once you get up and move on top of the water the hook catches and lifts the nose, then it drops, then it catches again and up it goes and so on. It is easily casued by people not supporting the transome on the trailer but letting it hang off the bunks, with a motor on it. As you drive and bounce it the bottom of the hull flexes until it developes a hook from side to side. Not something you want.

Finding the proper pitch prop usually takes a little trial and error, find the manufacturer's top RPM range for that engine, run it without a full load to get a prop that sets you up on the top end of your top RPM range, that way when you are loaded it will run still in that upper range.