1981 Johnson 35 blown HG-Head is off

[thehermit]

OK gang,<br />Just inherited a 1981 (thanks Vic) Johnson 35 HP. The guy who gave it to me overheated it before killing it trying to pull a fat guy up on waterskis. Copression was bad on lower cyl so I pulled the head. Head is off and cyl walls look Good, almost nice. You can see evidence (milk) of water intrusion in lower cyl. <br />My qusetion: If I slap a head gasket on what are the chances everything will be hunky dory? I am told the motor died all at once so I dont know how much damage was done before the blowout. But when water gets into a cyl does it trash the rings automatically??<br />Thanks gang!

 

[Chinewalker]

Re: 1981 Johnson 35 blown HG-Head is off

Hi Hermit,<br /> More than likely the blown headgasket caused the overheating and power loss. A blown headgasket allows exhaust to get into the cooling passages and water into the cylinder, neither of which is a good thing, but certainly not necessarily a death blow by any means. If all looks well inside, then throw a new head gasket in there, torque it properly and have at it...<br /> If no one else beats me to it, I'll try to dig out the proper head bolt torque number.<br />- Scott

 

[thehermit]

Re: 1981 Johnson 35 blown HG-Head is off

Chinewalker,<br />I think when the water got into the cyl it stopped the motor from running. The cyl walls and cyl head look good. I oiled up the cyl walls and cycled the motor a bit and it seems both look fine. Both cyls seemed to function the same. I am going to try to get the head gasket for it. <br />Torq #s would be great if you got em.

 

[rodbolt]

Re: 1981 Johnson 35 blown HG-Head is off

carefully check the head surface for flatness. they like to warp a lot. that motor is rather sensitive to overheat and pulling a fat guy wont overheat it. it may overload it and detonate a piston but if the cooling system was in good shape I doubt it would overheat, a blown head gasket is normaly a symptom not a cause.

 

[thehermit]

Re: 1981 Johnson 35 blown HG-Head is off

rodbolt,<br />you are correct! It was a symptom of a totally gonzo T-stat and an ugly water jacket. It is all clean now and back together (head and waterjacket). The head look OK but I will check it again for warping. No pistons have detonated just yet I hope it will run again!<br />TORQ specs anyone?????????

 

[Joe Reeves]

Re: 1981 Johnson 35 blown HG-Head is off

18 to 20 foot pounds in the following sequence.<br /><br />9..10<br />5...6<br />1...2<br />4...3<br />8...7

 

[rodbolt]

Re: 1981 Johnson 35 blown HG-Head is off

trust me and check the head with a .004" feeler gauge and a straight edge. that motor uses a siamesed cyl design with an open deck and is notorious for warping heads and popping the head gasket. if its more than .004" out of true you should really really get it fixed or it will most likly pop again.

 

[thehermit]

Re: 1981 Johnson 35 blown HG-Head is off

I checked the head with a metal straight edge. Looks good. Head is back on and torqed. <br />related Q: What if I put in a new tstat without that rubber seal????

 

[MCM]

Re: 1981 Johnson 35 blown HG-Head is off

Why would you want to leave the seal out?

 

[thehermit]

Re: 1981 Johnson 35 blown HG-Head is off

MCM,<br />Not a question of want just an oops. I forgot to order it so I put in the Tstat with OMC gasket seal for now-fix later if motor is still good.<br /><br />Status: head is back on and after a brief mix up with the coils the engine started right up and runs fine!!!!! Real fine!!<br />Compression check is next once I can locate the tester.

 

[thehermit]

Re: 1981 Johnson 35 blown HG-Head is off

Gang, Compresion came back around 130-135 for both cyl <br /><br />Motor is back in working action! Pretty good for a free motor...40 bucks in parts and its ready to go back out there! No more pulling fat guys!<br />TH