Need Advice for Prop-T-'89 OMC Cobra's

[rybad]

I know this is a difficult question to answer, but I'm hoping some of you with experience swapping props can help. I have never deviated from factory props before, and my boat neighbor gave me a set to try out, because on my boat, I spin around 3600rpm and run around 29MPH - he gets 29MPH at 3200 rpm.. and who doesnt want to save gas these days!?

Here are my specs.

1989 Four Winns 285 Vista ('29, 10' beam) appx. 10K pounds - Twin OMC Cobra 5.7/350 230HP.

29MPH is good sea conditions (2-3' waves, 10-15mph wind) @ 3600 RPM

15"x17p SS props.

My boat neighbor has a spare set of 14x20 props, but that are for a Merc. Alpha-1 drive (not sure if I can borrow these or not... that is the first question)

Also, looking for suggestions on the best props for this configuration. I'm more concerned about fuel econemy over hole-shot. I don't mind tabbing down to get on plane.

Any suggestions will be greatly appreciated!

-Dave

 

[walleyehed]

Re: Need Advice for Prop-T-'89 OMC Cobra's

To plane quickly and EFFICIENTLY, you should always put the tabs down for take-off
If you're saying 3900 is your max RPM, you're lugging the snot out of it, and fuel economy is going to be really bad compared to what it should be.
"If" you're just giving cruise RPM, that does no good in recommending a prop size.

The Alpha props will not go clear on the OMC prop-shaft.