Wrecked boat, repaired now problems with rpm.

[mxcobra]

Pulling my hair out here, haven't had the boat out much last few seasons. Because my launch and rpms are not acting right. First off I hit something in the water and destroy my outdrive. I replaced the out drive. with A used craigslist unit. It has V8 stamped on it. But with my old trusty stainless steel 17 pitch prop. Will not rev past 3,000 rpms. boat is A 1976 stock it had A MerCruiser sterndrive 898. Boat was fast ran great before I wrecked it. MY question is. If my new drive came from a boat with a big block, would that be enough to affect the performance this bad? I have gone through the rest of the motor everything checks out. Should I just repitch prop. Or start looking for another drive?

 

[alldodge]

MY question is. If my new drive came from a boat with a big block, would that be enough to affect the performance this bad?

Yes
If drive ratio is higher (sounds like it is) then you need a lower pitch prop. Not likely to find a prop lower then 17

 

[jimmbo]

Being that 'V8' covers a variety of Engines, it is entirely likely you ended up with a Different Ratio. Your engine likely has a WOT range of 3800 - 4200 rpm, so you are a little high in pitch, but as mentioned it might a bit harder to find a Prop low enough in Pitch, and props less than 17" tend to be designed, bladewise, more for Barges, and not for Speed. A different drive with the correct Ratio would be the best Solution

 

[mxcobra]

Now I am wondering, If I could just switch out the gears from the old unit, to the new unit.

 

[mxcobra]

Looks like iboats has A 13 pitch prop. But man I think top speed is going to suffer big. If I use that prop?

 

[alldodge]

Now I am wondering, If I could just switch out the gears from the old unit, to the new unit.

You could but need all the special tools to set preload and tolerances

Looks like iboats has A 13 pitch prop. But man I think top speed is going to suffer big. If I use that prop?

Maybe, but if you could find a prop shop, many times they let you try props.
It's usually buy the prop and it will be exchanged

 

[mxcobra]

You could but need all the special tools to set preload and tolerances


Maybe, but if you could find a prop shop, many times they let you try props.
It's usually buy the prop and it will be exchanged

I am in Colorado not many prop shops here, the one we had closed shop maybe 10 years ago.