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projector163

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"I replaced my upper omc cobra

"I replaced my upper omc cobra outdrive with a rebuilt upper drive with 21:18 gears, which they told me is what I had from my serial number on my drive. I took the boat out and the rpm at full throttle is almost 5000 at about 32mph before it went bad it was about 4000 at about 32mph is this the right drive or is there something else wrong."
 
"It almost sounds like you are

"It almost sounds like you are under propped, what size/pitch are you running? Going up in pitch by 4" could bring your RPM down to around 4200-4400 and probably see an increase in speed of a few mph. I wouldn't run at 5000 very long or bad things are going to happen! What's the torque like, is your hole shot strong?"
 
The gear set could have been c

The gear set could have been changed in the old drive at some point. I agree with Bob on going up in pitch.
Nothing wrong with throwing a bigger prop if you can.
Should cruise at a lower rpm with no speed lost = less throttle = less fuel.
 
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