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Missing RPM

E

ed_v

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"Hi I have a boat with 350 MPI

"Hi I have a boat with 350 MPI mercruiser year 2006.
My problem is that the max.RPM is +/- 4350.
What I do smaller props changing sensors, injectors or computer. no air leaks, compression and fuel pressure is good and the engine runs fine but not more then +/- 4350 RPM.
My friend have the same boat and engine but runs faster and rpm is about 5000.
crazy.gif

Have any one the same problem or knows what wrong with my engine.

Thanks,

Ed"
 
"Hello Ed:

I have a 18'

"Hello Ed:

I have a 18' Stingray w/ a 3.0L w/ the same issue. Seems like most other folks with the same boat can run a 21 Pitch prop and see close to 4800 RPM's. While I could only see 3700 RPM's with the 21P prop. I had to go all the way down to a 17P prop to get my RPM's around 4400. I've done all my own testing w/r/t compression tests etc... It is possible that lack of get up and good could be caused to a defect in the hull a "hook" / "power hook" can cause this problem providing everything else is OK. It is also possible that the othdrive is mounted too low on the transom as well. That would be strange for the outdrive to be mounted too low. Most manufactures have jigs as to where the cut out is located. Very possible it is a "hook / power hook defect"

Take care,

T."
 
Ed: what prop is your friend

Ed: what prop is your friend using and what prop are you using? Do you use your trim when you are at WOT? Or do you run with the OD in the full down position? Trimming the OD to the max RPM under way makes a difference in your RPM range. Guy
 
Ed; you should take off the fl

Ed; you should take off the flame arrestor and open the throttle wide and make sure that your throttle plate is opening fully.
Another thing to check is if both boats have the same drive leg gear ratio; though they should be both 1.50/1.47.
Rod
 
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