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Overheated Johnson 200 hp

D

DannyC

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" Joe, I blocked off the wate

" Joe, I blocked off the water intake on my 1990 200 hp Johnson and did not notice that I wasn't putting out water on the tell-tale. I noticed when the motor started smoking from under the cover. I was sleeping on the boat in the backcountry and it was near dark, so I figured I'd just camp the night, and try to clear the blockage in the am. Next morning when I turned the engine over it did not sound good at all (I made a couple of turns only), so I did not try to even start it. Got towed in and plan to work on the motor over the weekend. What do you recommend about checking on possible damage to the engine? As always, your help and advice is greatly appreciated.
Danny "
 
"Danny.... Eeewwww! Bummer! Wh

"Danny.... Eeewwww! Bummer! When a mistake is made such as that, and the powerhead gets so hot that it smokes, cylinder head bolts etc come loose, wiring insulation melts and causes shorts, water may enter the cylinders due to the loose head bolts and damaged gaskets, etc etc.

Of course you'll need to replace the water pump assy, and I'm afraid that a rebuild of the powerhead is usually required. However, check the s/plugs for traces of water. Tighten the cyl head bolts (torque 18/20 ft lbs). Also tighten the bolts retaining the powerpacks, grounds, etc etc. Check closely all of the wiring and repair as needed. Test run the engine as you've nothing to loose at this point. If you're lucky, a few minutes running may return the engine to normal.... and if so, install new cyl head gaskets. If within a very short time of running, you hear clanking, clunking, sounds that don't belong there... shut the engine down to prevent further damage, then prepare for the rebuild process.

Joe
"
 
Thanks a lot for the response

Thanks a lot for the response Joe. I sure hope I'm lucky! I'll let you know what happens.
Danny
 
" Joe, I don't know if I&

" Joe, I don't know if I'm lucky or not. I took off the lower unit, and surprisingly the water pump was all right. I thought I had sucked up mud without noticing, but it was clean, the rubber looked perfect. Water went thru the lower unit (with the unit off) with the ears on. I pushed the hose up the shaft, and I was getting water out the telltale. I pushed a small brush up the shaft, and it came back with no mud or other gunk, clean. ??? I'm going to take the lower unit to a shop tomorrow and have it presure tested. As for the motor, there was no water in the spark plugs and the presure was, from top down and from port to starboard, 100, 90, 70, 95, 75, 70. The last time I checked, they were all in the 90's with very little difference. Hopefully, once I get it all tightened up, the pressures will even up.
I will keep you posted on what else I might find tomorrow. I'll keep my fingers crossed.
Thanks,
Danny "
 
"Danny.... After reading that

"Danny.... After reading that the water pump appears to be perfect, I would say that it's possible that a head gasket failed, allowing exhaust pressures enter the water passage areas. This would create a condition whereas the exhaust pressure would meet the water pressure which would create a stalemate. This would cook the powerhead as you explained it. I would now recommend that instead of trying to start the engine, remove the cylinder heads, and inspect the sealing surfaces of the heads & block, the gaskets, and those water deflectors.

Joe
"
 
" I'll do that and keep yo

" I'll do that and keep you posted.
Thanks,
Danny "
 
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