'97 Force 75hp prop question

[slayer1660]

Got a 1997 75hp force on 17' nitro with a 10.25" by 14p prop. It seems to take forever to plane out and was wondering if a smaller pitch prop may help. WOT is 5500rpm @ 35mph. Thanks for any help!

 

[steelespike]

Re: '97 Force 75hp prop question

"Forever to plane out"can you define that in seconds?Details on the boat?
Max hp rating?Glass, Aluminum?
Rpm and speed seem pretty close to normal.
Is the antivent(cavitation)plate even with the bottom of the boat?
Do you trim in for hole shot? Reducing pitch would help hole shot but a
12" would be close to what you would put on pontoon.Is the gas tank,battery and anchor etc at the stern?
Sometimes older boats have absorbed water along the way putting a couple of hundred pounds right at the stern.

 

[slayer1660]

Re: '97 Force 75hp prop question

"Forever to plane out"can you define that in seconds?Details on the boat?
Max hp rating?Glass, Aluminum?
Rpm and speed seem pretty close to normal.
Is the antivent(cavitation)plate even with the bottom of the boat?
Do you trim in for hole shot? Reducing pitch would help hole shot but a
12" would be close to what you would put on pontoon.Is the gas tank,battery and anchor etc at the stern?
Sometimes older boats have absorbed water along the way putting a couple of hundred pounds right at the stern.

max hp rating is 125
fiberglass
not sure about the cavitaion plate (dont know what the hell it is)
3 batteries at stern, with 24 gal fuel tankn
the holding water thing makes sense but i am hoping its a wrong sized prop
thanks for reply!!

 

[Frank Acampora]

Re: '97 Force 75hp prop question

I just rebuilt the exact same engine on a 16 foot nitro. During the shake-down cruise with a 10.25 X14 she turned 6000 WOT with three people in the boat--one in the front. However, the boat is so tail heavy that it needs at least 1/2-3/4 throttle to just get up onto plane and it drops off plane if RPM is less than around 3000. And yes, even at full throttle, It takes a long time to get up on plane. I did recommend going up to a 16 pitch prop to bring down max RPM, and that will slow down the hole shot even more. I don't remember exactly, but top speed was acceptable

I would say with that engine and boat combo, you are going to need to live with it. Prop change will not help, but trim tabs are probably a necessity.

I don't understand why Merc would take a nice mid sized engine and equip it with an itty-bitty prop that is usually used on 30-50 HP engines. Even looking at the engine with the boat on the trailer, the prop looks like a toy. before the shake-down, I had doubts that it would even adequately move the boat.