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‘76 6 HP hard to pull over. Reading higher than spec compression

ScottLynds

New member
Hi, I have a 1976 Johnson 6 HP that sat for several years but had run well prior to that. I have been trying to get it running again but when I pull the start cord the engine is very hard to turn over. I checked the compression and it is reading 112 psi on both cylinders when I understand the spec is 85 to 95. Any ideas on what may be causing this and remedies for it. Thanks, Scott
 
Welcome to the forum. Very strange. Hard to pull over is usually something in the lower unit. Was is stored with fresh gear lube? I think your compression gauge needs replacement, my friend. Do you have something else to try it out on? Most 6 hp I work on are about 65 to 85 lbs. They run quite well at anything over 60.
 
Welcome to the forum. Very strange. Hard to pull over is usually something in the lower unit. Was is stored with fresh gear lube? I think your compression gauge needs replacement, my friend. Do you have something else to try it out on? Most 6 hp I work on are about 65 to 85 lbs. They run quite well at anything over 60.
I took the lower end off yesterday to see if that might be the case, but it didn’t change anything. I put oil in the cylinders and let it soak for a day and that made a little difference it seems. My compression gauge has been accurate up until now but could use it in my new 6hp merc as a comparison next time I am down to the marina
 
Where it was stored, could it have gotten moisture inside? If the head gasket hasn't been changed yet, now is the time to do it. The Sierra gaskets are improved over the old style. Surface the head on a good flat surface and use 180 grit wet or dry paper with soapy water. Clean threads well and use a little bit of anti seize compound to replace the lost zinc coating on your bolts. Replace thermostat, they are a common failure.
 
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Where it was stored, could it have gotten moisture inside? If the head gasket hasn't been changed yet, now is the time to do it. The Sierra gaskets are improved over the old style. Surface the head on a good flat surface and use 180 grit wet or dry paper with soapy water. Clean threads well and use a little bit of anti seize compound to replace the lost zinc coating on your bolts. Replace thermostat, they are a common failure.

After another day of soaking the compression in both cylinders is down to 100 psi and it is easier to pull her over a little. There is spark so I put a little gas in the cylinders and it started up for for a second or two. I am going to soak it some more and keep pulling her over each day for the next couple of days then see if I can get it running in a tank. ( once I put the bottom end back on LOL .)
 
Pull the cylinder head and inspect stuff.----Head gasket is $20 or so.----Loosened up a 1975 6 HP that was stuck from sitting.-----Took it apart for inspection.-----Found rings jammed and corrosion on crank and bearings.
 
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