new ss prop 5.7

[mjhehn59]

I currently own a 94 Cobalt 20' open bow. It has a 5.7lx Merc V8 alpha 1. It is either 235hp or 260hp. I am running an alum 14.5 x 19 prop. With only myself in the boat and a full tank at wot 4800rpm the boat will run 51mph. I want to purchase a ss prop to increase top end. Any suggestions about changing dia or pitch to achieve this. Will it change my wot rpm. What would my expected top end increase to. I current use the for my kids to waterski.

 

[jestor68]

The same pitch Mercury Vengeance ( 14 X 19 ) would be a reasonable upgrade for a predictable result; better acceleration and slight speed increase.

The Mercury Enertia ( 13.8 X 20 ) would be a more serious upgrade. This prop uses Merc's PVS venting system for increased acceleration and top speed over the Vengeance. It would likely run a little lower rpm(-200?) at top speed while picking up 2-5 mph over your aluminum prop.

Bear in mind just you in the boat may not represent the "normal" load. Don't make the mistake that many do by propping for max speed with no load, and have it fall on it's face when you put a few people in there.

Prop selection is always a compromise.

 

[mjhehn59]

Thanks jestor68 for the advice. Just a comment relating to the normal load. With a normal load in the boat (3 adults and 2 teenagers) full tank. The boat will run about 48 mph at the same 4800 rpm. Not too much difference in top end. The boat weights 2800lbs. I've got a prop repair guy in the area, he is recommended to be a prop expert maybe he'll loan me a prop to experiment.