2001 25hp Yamaha max speed?

Snorks

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Ugg. Just bought a 2001 Yamaha 25hp short shaft tiller - pull start no electronics. I put it on a 14' StarCraft DLX (400lbs). Two of us in the boat weigh another 400 pounds.

The speed is around 7mph full throttle. The dealership is saying that I should get a new prop and this will solve all the problems. To say I have my doubts is an understatement.

Can anyone point out some probable causes? I replaced an old Tohatsu 2 stroke that moved us around 20mph no problem at all.

Thanks for any help.
 

Snorks

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9 7/8 x 10 1/2 -F
RPM -- No idea . But they said it had low RPM. (3000?)

He recommends:
​​​​​Yamaha 664-45943-01-00 Propeller (3X9-7/8 X8 -F); 664459430100 Made by Yamaha
 

99yam40

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hard to say if RPM is not known
rule of thumb was 200RPM per inch change, but is when the motor can get the bot up on plane

you sure do not give much info when you say old motor

what HP was the old motor and what prop did it have
 

Snorks

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Tohatsu was a 2000 two stroke. It really smoked and didn't idle well . It also seemed to have a limit at the 18-20mph range... But at least it went that fast . This 4 stroke isn't even in the same ballpark.
 

99yam40

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now we find out you have a 4 stroke.
always good to post a complete model # when talking about a motor.

25 hp is still 25 hp.

find out what prop you were using on the old one, that should tell you about what is needed on the new

or find someone with a prop you can borrow to prove it will or will not help.

there is a possibility there is a motor problem, but you will have to figure out which it is/ motor or prop
 
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