5.7 to 5.0

[4winnssd]

Have a 1993 Cobra 5.0 v8 but need new outdrive. Is an outdrive off of a 1988 5.7 compatible?

Thank you

 

[bruceb58]

Typically, the 5.7 came with slightly different gearing. Otherwise, they are pretty much the same. You would have to reprop. Problem is, if you have a fairly heavy boat and already turning a pretty low pitch prop, you might not be able to go much lower. It's not ideal.

 

[Lou C]

In my OMC owners manual it gives the overall ratios:
5.0: 1.50:1
5.7: 1.41:1
so you can see the 5.7 is geared a bit taller for higher top speed, but you will have to go down in prop pitch to make up for it, not sure the weight/size of your boat...
On my 4.3, it came with the wrong prop for the engine/drive (1.68:1 ratio) which was a 14.5x19. I switched to a 15x17 which was better and wound up with a 15.5x15 which is the best of all for performance, it revs a bit higher than spec but that allows for the boat gaining weight over the years and numerous coats of bottom paint lol. 4900 RPM wide open.
One thing you DON'T want is to not be able to get the engine into at least the middle of your max RPM range spec. That is for the 305 (5 liter) 4200-4600. So you want at least 4300-4400, I prefer to prop at the top end, it reduces the load on the engine from pulling the boat up on plane.
What prop do you have on it now?

 

[4winnssd]

Boat is. 1993 Four Winns 190 Horizon. I'm not sure on the prop size, but if I can make that change and it works well I would like to do it. Save me about 700 over buying refurbished outdrive.

Or should I just spend the extra and get the 5.0 outdrive?

 

[Lou C]

the problem is no one can tell you it will make the boat perform the way you want it to. My inclination is to use the correct drive ratio.

 

[4winnssd]

Thank you, really appreciate the help

 

[jimmbo]

Would that Extra $700 include a Warranty?

With the Used Unit, you will have to Reprop, and if you use SS, there goes a lot of the $700 you saved

 

[4winnssd]

Was just told the gears in the 5.7 are 1.53. now I'm considering it again. What would it be geared like that?

 

[4winnssd]

Big thank you to those that responded, will be on here a lot going forward. Planning to restore my floor myself after I get this outdrive replaced. Thank you again