MerCruiser stuck on low RPMs

[AlexEDH]

Dear All,

Here is the problem: randomly my MerCruiser gets stuck at 2000-2500 RPMs and does not go further. This may last from minutes to an hour, then gets back to normal operation.
Service guys tried to reproduce it couple times, but failed.
Some details, may be just a red herring:
- Observed on mountain lakes only, at elevation > 5000'
- Noticed after we hurt a rock and damaged the prop
- At the straight course the boat has a small, but noticeable tilt on the port side, 2-3 degrees, may be (I also have a hydrofoil installed, it may be the reason)

Two reasons come to mind:
- Lower air pressure, not enough oxygen, but this seem odd
- The outdrive was hurt either and is out of balance (Is it possible to detect and fix it, if so?)

May be some other ideas?

Thank you,
Alex

 

[alldodge]

randomly my MerCruiser gets stuck at 2000-2500 RPMs and does not go further. This may last from minutes to an hour, then gets back to normal operation.

Its a Merc, but how about carb, EFI, MPI, 4, 6 or 8 cylinder motor, what year, and better yet what is the serial number?

What is normal high rpm?

 

[AlexEDH]

As far as I remember, it is 4.3L MPI 190HP ECT, 6 cylinder, injector. The boat is 2009.
The red line is close to 5000.
Serial number can figure out later.

 

[alldodge]

WOT of the 4.3 is 4800, and being a 2009 the HP should be closer to 210 at sea level. Being at 5000 feet, this will be down a bit. When the boat allows higher then 2500 rpm's, how high does it go?

If the boat was taken from sea level to the higher altitude you need to reduce the prop pitch and maybe even change the drive ratio

 

[AlexEDH]

Upd. Just talk to my wife, she says same glitch happened at our favorite lake, which is about 450'. And she confirms this started after the damaged prop.
Normally motor easily goes to 4500, even at high elevations.

 

[alldodge]

Then go thru this list of possible causes for low WOT

http://forums.iboats.com/forum/engi...6-list-of-possible-causes-of-low-wot?t=295070

 

[AlexEDH]

Thanks a lot, I will try!!!