OMC IO changed upper gearbox rpm to hi, what size prop?

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lake11

Cadet
Joined
Apr 22, 2007
Messages
15
I have a 1985 OMC Stringer 5.0L. The old upper model 983488 (21/17)was destroyed. I think the lower is a 15/23. I replaced it with a 981060 (not sure of the ratio). I took it out and was able to get RPM past the limit. Speed was in the 28-30. Felt like I was only about 3/4 throtle. Can I just change the prop? And to what? THX
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: OMC IO changed upper gearbox rpm to hi, what size prop?

I'm not an expert but we need more info; past what limit?What is the max recommended rpm.What boat are you running.What was the original max rpm.,
speed and prop? What is the present prop?
 
B

Bondo Again

Seaman
Joined
Jun 7, 2008
Messages
53
Re: OMC IO changed upper gearbox rpm to hi, what size prop?

Ayuh,...

It sounds like you went to an extremely Low gear ratio,....
And....
You'll probably Never find a prop that'll make up the Difference.....

You need the Right outdrive 1st....
 
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