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First project 1972 20hp Johnson

W

Wilbev

New member
This is my first “build” and I’m scared. I just did the points and a carb rebuild just to find out that the bottom cylinder has 100psi and the top has 40 ish psi I don’t know we’re to begin can someone help

I was thinking head gasket I guess there’s only one way to find out huh
 
Yep, take off the cylinder head and have a look at the gasket and cylinder walls. Is it a freshwater or saltwater engine?
 
fitz73222 said:
Yep, take off the cylinder head and have a look at the gasket and cylinder walls. Is it a freshwater or saltwater engine?
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I’m 90% sure it fresh water all its life but I took off the head and the bottom one was fine as expected but the top had some pretty good scars on it are there and bored over kits for a 1972 20hp? Might just bight the bullet and do a mild build or get off while i still can
 
You can get OS pistons for it. You'll have to decide if it is worth fixing or not. Have you ever run this motor? Does it have good spark that jumps a 1/4" gap? No water water in the gearcase? Good forward gear clutch dog that doesn't jump out of gear? These projects can go from simple to a money pit, but they're great engines and much better than anything 4 stroke being produced today. I have a pair of them I bought in the shop right now, a salty '72 18 and a super clean Canada freshwater '73 18 with a botched cylinder head repair. I do love these motors.
 
fitz73222 said:
You can get OS pistons for it. You'll have to decide if it is worth fixing or not. Have you ever run this motor? Does it have good spark that jumps a 1/4" gap? No water water in the gearcase? Good forward gear clutch dog that doesn't jump out of gear? These projects can go from simple to a money pit, but they're great engines and much better than anything 4 stroke being produced today. I have a pair of them I bought in the shop right now, a salty '72 18 and a super clean Canada freshwater '73 18 with a botched cylinder head repair. I do love these motors.
Click to expand...
No never run i just hate to see it go like that I did the points changed them did a carb rebuild and the foot a little water not much but I got the wrong water pump for it just got to get fluid I haven’t checked anything else I mean it goes into gear all the way when I spin the prop took off the head and the head gasket is bad as-well wanted to take off the exhaust side for fun now that I’m in it and broke a bolt so I don’t know hopes are going down
 
Clutch dog and forward gear issue isn't realized until running on the boat under load and it jumps out of gear. It all depends how it was treated in it's past life. Any water in gearcase means a re-seal job or at least a pressure and vacuum test to see which seal is bad.
 
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