OMC King Cobra Noise

cthamil

Recruit
Joined
Aug 22, 2007
Messages
3
I just bought a 1994 Chris Craft 25' Cruiser with a 5.8 OMC with an Omc King Cobra drive, before I took it out I changed the oil, plugs, drive oil, and impeller.
I took it out 2 or 3 times and all was good except WOT RPM's were a little high
because of a corroded prop. I got a new prop 15x17 and it runs even better but RPM's are still high. The problem is that I started to notice a a sound at low RPM's only when it's put into gear, the sound is like a bearing going out but it still runs great, so I put the old prop back on to rule out a problem there. I have changed the drive oil again and it was perfectly clean and yes I am filling from the drain hole very slow. From looking at the service manuals I have I believe the sound would be in the lower unit.
Any help would be great. Thanks
 

cthamil

Recruit
Joined
Aug 22, 2007
Messages
3
Re: OMC King Cobra Noise

WOT should be at 4500 and I am getting about 5600 the only thing I can think of is the prop is slipping or ventilation.
Thanks
 

thrasher

Chief Petty Officer
Joined
May 23, 2007
Messages
443
Re: OMC King Cobra Noise

I'm not sure anything is slipping, a 17" pitch on a 5.8L engine sounds to small to me!! I would have expected something in the 20's pitch wise.. If the prop does not have enough pitch it will allow the engine to over rev.. I run a 19" pitch on my 21 footer with a 4.3L engine (Alpha 1 gen 2 drive)..
Not knowing the king cobra drive I can't offer any suggestions about the noise, but as winter is not far away, it sounds like you have a nice project to keep you busy over the winter (dismantling the outdrive).

Gary
 

alaska_av8r

Petty Officer 2nd Class
Joined
May 28, 2007
Messages
184
Re: OMC King Cobra Noise

a doctors stethoscope or piece of water hose may help you isolate the noise.
 
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