What Prop on a 5.7

[PeteyDaMan]

I have an 83 SeaRay SRV195 (V hull, 19.5ft) with a Mercruiser 260 (5.7).
I just rebuilt the top end with new valves, manifolds, risers and gaskets and want to figure out if I have been running the right prop or not. I've been using a 15x15 aluminum 3 blade for the past 5 years but I'm starting to suspect that I shoud be running a 17. At WOT I'm typically up around 4800 and I'd like to bring that down to around 4200 as the motor is a little on the old side.

I'd like to stay away from stainless.

The boat is used mostly for tubing and needs a good hole shot.

 

[QC]

Re: What Prop on a 5.7

Welcome aboard Petey!!

Well . . . I wouldn't consider bringing your WOT down to 4200 as a conservative approach for an old engine. May actually work out to be harder on the engine as it increases load at all points . . .

I am struggling with a 15 on a 19 footer with a V8 though . . . What top speed? Gear ratio?

 

[steelespike]

Re: What Prop on a 5.7

I agree leave the rpm as is just control your rpm with the throttle.
Also as suggested a 15 prop on that setup... something "ain't" right.
Hole shot should about throw you out of the boat and probably be running
5,500 rpm. Are you sure your not missing a cylinder or throttle not opening all the way.All carefully timed/tuned?How is the compression?

 

[hwsiii]

Re: What Prop on a 5.7

Error

 

[hwsiii]

Re: What Prop on a 5.7

Petey, you need a 16" Pitch for your setup if you have a 1.32:1 gear ratio as I show you have, and it will turn between 4,400 and 4,500 RPM which is right at top of max RPM without going over, But you do want to keep your max WOT RPM at top of the recommended RPM range, or you will be lugging that engine which is as bad as overreving in the long run. But run the motor at a cruising speed of 3,200 to 3,500 RPM to make it last longer for everyday use. QC and steele are absolutely 100% right, they know what they are talking about. Your hole shot will lose a little bit but not much.


Prop Picker

H