Prop Question

[mepearson]

Looking for opinions:

I have a 1986 Cobalt 21 BR with a 260 hp Mercruiser Alpha One 5.7L V8. I run with a pretty heavy load. Usually at least five people plus fuel in the boat. The Boat has a dry weight of 3600 lbs.

I'm thinking of putting on a four bladed 14.5" aluminum prop with a pitch of 18. I'm less interested in top end speed and more interested in power out of the hole. My WOT is 4200-4600.

Thoughts?

 

[Silvertip]

Re: Prop Question

Can't give you advice since you failed to indicate what prop you have now. But the current WOT rpm looks like the prop you have is pretty close to what you need. Propping for hole shot means you sacrifice top end and that means the engine revs higher than it would have if propped for recommended WOT rpm with what you consider an average load. That also means the engine is reving higher across the band and therefore consuming more fuel. You can't have top end, hole shot, and fuel economy all in one package. Props are a compromise.

 

[mepearson]

Re: Prop Question

Can't give you advice since you failed to indicate what prop you have now. But the current WOT rpm looks like the prop you have is pretty close to what you need. Propping for hole shot means you sacrifice top end and that means the engine revs higher than it would have if propped for recommended WOT rpm with what you consider an average load. That also means the engine is reving higher across the band and therefore consuming more fuel. You can't have top end, hole shot, and fuel economy all in one package. Props are a compromise.

Thanks. The current prop is a 3 blade, 14" prop with a pitch of 19>

 

[jestor68]

Re: Prop Question

And, what rpm does it turn at full throttle with your "usual" load on board now, with the 14X19?

 

[steelespike]

Re: Prop Question

Looking for opinions:

I have a 1986 Cobalt 21 BR with a 260 hp Mercruiser Alpha One 5.7L V8. I run with a pretty heavy load. Usually at least five people plus fuel in the boat. The Boat has a dry weight of 3600 lbs.

I'm thinking of putting on a four bladed 14.5" aluminum prop with a pitch of 18. I'm less interested in top end speed and more interested in power out of the hole. My WOT is 4200-4600.

Thoughts?

Are you saying your wot rating is 4200 to 4600 or are you saying your making 4200-4600?
What size is the present prop.
The only way to evaluate your setup is to make a lightly loaded wot run and get us the rpm and gps speed.
and remind us of the prop size.