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Cylinder Head Water Jacket Hole

davenaus

Member
I had poor compression on one cylinder of 2003 Tohatsu 8B 2 stroke engine.Took off head & found corrosion in water jacket. As I cleaned up corrosion a hole opened up at lower corner of water jacket. I am uncertain if it is part of design or at least ok as part of water system or I have to weld the hole shut. Can someone help advise? I recognize the corrosion around the cylinder walls yet hope that a new gasket will create needed seal. Thanks in advance. David
 

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Have reassembled motor and given it a cold and warm(after running for 5 mins) compression checks. Results the same as before breakdown, cold and warm compression tests. Upper cylinder 90psi, lower cylinder 60psi. I noticed some damage on the lower cylinder inner wall near where the plugged water jacket hole and outer wall damage was. I smoothed it out with some very fine sand paper but still have only 60psi. Is there something I can do to repair the engine minus a complete teardown, new core and rebuild? Thinking the engine has just become a parts source for someone else. True? Shame because it was a very nice little motor. Very efficient & powerful for the size.
 
You could hone the cylinders and install new rings.

To do that I'd need to disassemble the motor to remove the pistons, then hone, then new rings, reassemble. Still have a core with corrosion damage and less than ideal walls in water jacket. The cost and time to complete what you propose seems to be beyond me. Maybe there is an easier way but not seeing it. Cheers & thanks for dialogue, David
 
The motor needs to come apart , likely one new piston & rings.----No other proper way to do this.------A new motor for some is the best option.----If you have lots of coins you do not have a problem
 
Thanks Racerone. Was using the motor for a tinny that I was rarely using. Thinking of selling the tinny now. Problem probably developed as I wasn't using it enough. Don't see that changing much in the future.
 
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