200 HP Johnson-detonated/burned powerhead

Jack Olinger

Recruit
Joined
Dec 8, 2000
Messages
1
I have a 1995 Johnson Limited Edition, 200HP outboard. At end of this boating season the motor made astrange noise and I immediately trailered and took it in for check. The mechanic said I detonated the piston. The piston and power head are aparently ruined. There are holes in both. It was explained to me that this was caused by running too lean or out of fuel. I run with a tach. I have been using a 4 blade OMC prop <br />(Viper 22 pitch - not sure right now on pitch?) . My boat is a 20'4" Concord and at extended full throttle the motor tachs at 6000. 95% of my boating is pulling knee boarder and wakeboard at 3000 rpm. Has anyone else blown a power head on one of these engines? I hate to spend $3500 plus to rebuild an engine prone to this catastrophic failure ove fuel too lean.
 

corm

Lieutenant Junior Grade
Joined
May 12, 2000
Messages
1,241
Re: 200 HP Johnson-detonated/burned powerhead

Hi Jack,<br />Your gas probably had to much alcohol in it.<br />Running your motor at 1/2 speed gives you max spark advance and maybe 1/2 gas flow.<br />causing a leaner running motor,which is no problem if you have good gas in it.<br /><br />corm
 

ICEMAN

Petty Officer 1st Class
Joined
Dec 11, 2000
Messages
292
Re: 200 HP Johnson-detonated/burned powerhead

Another possibility is a restriction in a carburetor jet or passage which would lean out that cylinder. Have your tech. go thru the carbs and the jets.
 
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