1968 Johnson 65hp Low compression?

mars bar

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Did a compression test on this motor and here are the results. Cold engine Cylinder 1 -80 lbs. 2-70 lbs 3-90 lbs 4-90 lbs. Let it idle for a bit and these are the results cyl 1- 80 lbs 2- 60 lbs 3-85 lbs 4- 85 lbs. Sounds like head gaskets ? Look at cylinder # 2
 

mars bar

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Runs fairly smooth, idles well. It run hot for maybe 30 secs. before I noticed no water exhausting from back. What about checking head gaskets?
 

racerone

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Pulling the bypass cover lets you look at a piston and rings.--------Simple $2.00 gasket.--------Pulling the head requires a more expensive gasket !!
 

SparkieBoat

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It probably is ready for a rebuild, but you could try pulling the head and having it smoothed then a new gasket and do a good decarb, the process is easy and outlined in this forum. you may get another year or 2 out of it but it is not going to run great. unless it has sentimental value, you can get a good 1980s model 70 HP motor for around $700-1000. check compression should be around 120. make sure you hook up and test an overheat buzzer alarm.
 
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boobie

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I'd still pull the bypass cover first. You get a better picture of what's going on.
 

mars bar

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The #2 cyl had a rusty blow hole through the gasket as well as several other blow bys on the other side. I'm wondering if the fellow before me torqued the heads down properly. All I see are black spots. Got all new gaskets including water jacket for $50.
 

mars bar

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I think I found the problem. as for $700-$1000 for a good second hand motor I'll have to ask my Kids for the college money back LOL Thanks Everyone.
 

Crosbyman

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that head gasket wont solve your water pump issue. Better get some water flowing Inside. did u at least change the impeller on your new purchase ???

if you did..... you have a blockage...better find it !!
 

mars bar

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Two water pipes in the lower unit one from the impeller housing and the other a return pipe. In my haste I didn't make sure the impeller pipe was in fact in the housing ,it has a dogleg shape to it and revolved a bit to the one side missing the housing port hole. So no water was getting to the heads.
 
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