OMC cobra gear ratio

[rojoc]

I am in the process of reinstalling an outdrive on my 5.0 88' OMC. The boat is an 88' starcraft offshore fisherman 21' fiberglass. I would like to reinstall an outdrive that is a 5.7 omc just overhauled. I realize there is a different ratio between the original 5.0 and the 5.7 that I would like to install. What can I expect as far as performance, speed and or efficiency. Being the two ratios are as close as they are would a need for a prop change be necessary? Thanks all.

 

[Coors]

Re: OMC cobra gear ratio

1.5 compared to 1.41.
The gurus will chime in.

 

[HT32BSX115]

Re: OMC cobra gear ratio

Howdy,

My 87 service manual indicates what Coors said. 5.0L 1.5 and 5.7 1.41:1

You might have to use a slightly lower pitch prop for the higher ratio drive.....like using a 17 instead of the 19 you might have had on it.

TRY IT FIRST! You won't hurt anything. You have the ability to swap your engine in the future if you decide to go for a 5.7. You want the engine to turn close to the MAX rpm at WOT.

I have a 1.43 drive that would work perfectly with a 5.7. It was originally hooked up to a 7.5L engine.....It's a 1.43:1 drive. I suppose I should put it on ebay or something!...I need the floor space!


Cheers,