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new_kid

prop problem

13 posts in this topic

I bought a new prop because i wanted to run a little higher RPM on my motor i had a 12 1/2 X 13 and i purchased a 12 X 10.5 when i ran it tonight it would not get on plain it acted like it ran out of water and spun out. I would start going the boat would come close to the point of plaining out then it acted like a truck on ice the rpms would go up and the boat would start to slow down until i backed off the throtel then it woul pick up again only to spin out again I had the motor trimmed all the way down while testing any one have any ideas Thanks New Kid

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You probably went too far down in pitch, too flat of a prop, no bite. What were you running for rpms with the 13? What engine?

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with the 13 i was running 4500rpm the motor is sureposed to run between 4500 and 5500 rpms i was told 2 degrees of pitch would get me 500 rpms but they didnt have an 11 so i went with the 10 1/2

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If the motor height is correct and you were trimmed in all the way, then theres nothing really you can do except try an 11. The lower in pitch you go, the flatter the prop, its just not holding. 4500 is in the range, were you having trouble other than wanting more rpm on the top end?

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I have the same problem, although not quite as bad. I was having problem getting on plane with a 17 pitch, so went to a 15 pitch 13.5 on my Merc 4/str. Well similar problem, with two people in the boat at the windsheild seats the prop would break loose when I started trimming the motor up for cruising speed. Moved one person to the back jumpseat to hold the sterm in water and problem solved.

I believe the issue we both are having is a combination of two limitations. One of them being the aluminum props. The second being somewhat underpowered for our boat sizes.

Aluminum props not being as efficent as Stainless need a lower pitch to deliver similar performance, but as you reduce the pitch you also decrease "bow lift" which helps keep the stern in the water. Without it the prop "blows out" or starts to cavitate killing your performance. So like boatfixer says we're stuck with it.

My problem is the 17 pitch works fine for one or two people, acceptable hole shot, good r's and low 40's top speed. But I want to be able to pull water skiers and get on plane wit 4 in the boat. The 17 pitch wasn't able to get on plane with four. So the 15 pitch seamed to be the logical answer. And it does plane out great, but now I have the blow out problem.

It "blows" for both of us but the best solution appears to be a Stainless prop, I'm sure a 16 or 17(17 seeam to high to me) stainless prop should be the tiket for my set up. (1750 Lund Firsherman w/115 merc)

I have one question for anyone on this board, I've been told that a Merc. 115 Four stroke will not turn a four blase SS prop. Is this correct. Because I've also been otld that a 4 blade would be the best solution to my problems?

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Theres two other solutions no one has talked about. Adding Trim tabs to the back of your boat, or the big trimming fin they sell to your motor lower unit. They may work also.

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[quote name='

I have one question for anyone on this board' date=' I've been told that a Merc. 115 Four stroke will not turn a four blase SS prop. Is this correct. Because I've also been otld that a 4 blade would be the best solution to my problems? [/quote']

You can put a 4 blade one we set up lots of customers with those, but a nice 3 blade ss maybe all you need.

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Leech I already have a fin on the back of the motor so i have tried that and i dont have the cash to throw down 300 for a stainless prop and i wanted more rpm hopeing that it would help put me on plain a little faster. I know that my boat is underpowered but since i dont have the cash for a stainless prop i dont have the cash for a bigger motor the boat is rated for a 75 horse which would be very nice as the boat is only 15 1/2 feet long so until i have more money i was just trying to get a little better prop on it to help me out a little

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the prop i bought is a hustler it is made by turningpoint propellers and i want to say thank you to everyone for trying to help me with this proplem i apreciate any and all ideas

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