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Compression Problems 1981 Johnson 150 HP Mod J150tlcih

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bentonparkwest

New member
Did a compression check today, took out one plug at a time...went by the manual. Just got this motor off of craigslist...
Cylinders 2,4,6 were around 95-96 lbs
Cylinders 1,3 were 80 lbs
Cylinder 5 is only 50 lbs.
Checked it twice.
The head gaskets and the entire motor looks clean/good/intact.
The guy I bought it from had the wrong plugs and wrong gap on the wrong plugs...
What are the possibles here? Should I have the whole thing rebuilt or what are my options? Anyone know prices for rebuilding engines? Is it better to go get a different motor? Should I scrap it? I don't have any boat experience at all...just a little common sense.
Thanks
 
Take the head off the 1,3,5 side for sure.... check for any damage to the walls and ports. check the pistons for damage also, if all looks good, you can do a De-carbon to the motor and see if the rings are stuck.
the cost for a rebuild depends on the amount of damage done to the motor.
let us know what you find.
(I would pull both heads and do an inspection on everything)
 
These motors came from the factory with -------" pressure back " piston rings-------Many of these motors suffered from broken piston rings and thus the lousy compression test.-------------Then again it might be a blown head gasket.----------Pull the cylinder heads to inspect or pull the bypass covers ( cheaper gaskets ) to look at the pistons and ring from the side.-------Running an outboard is not the same as a car !!! -------Many motors suffer from the wrong set-up / wrong prop / cheap oil / lack of maintenance etc etc.
 
Keep in mind that the engine is 31 years old now and that a powerhead rebuild will hit $2000 plus easily, some twice that.... just depends on the damage.

Your post sounds like you've already had the cylinder heads off but that may simply be the way you explain things. However, if you haven't already, remove the cylinder head and inspect the head gasket, pistons, and cylinder walls closely.

Since the compression has affected all three cylinders, there is a good chance that the starboard bank has overheated or encounted some other problem that has simply resulted in blown head gasket.

Let us know what you find.
 
Thanks, I didn't take off the heads yet, just inspected from the outside and pulled the plugs. I was just going by the look of the paint/gaskets/general condition of the outside....the fact that it cranks over, which is all I could do at the time. Will take off the one side and let you know what I see and go from the there...Thanks
 
Ya, well, I am totally efffed. Pulled the heads and inspected. Pistons and head on starboard side have tons of gouges and pieces of metal in there. Pictures 123.jpgPictures 127.jpg
 
Yep, that's the best route to take. Hopefully you don't have too much invested in it. And now you know why the guy had it for sale.
 
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