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Johnson 1990 90 hp bolts

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riopga

Regular Contributor
Are there any tricks to removing the head covers? I am worried about broken bolts. Is sudden sharp jolts better than slow steady pressure? What about an impact driver? Heat?

I think I need to change the water deflectors. There seems to be an internittent overheat. Twice recently it seemed to run fine all day, but then as I came back to the dock and idled down the overheat alarm went off.

I did recently replace the entire water pump assembly, but I have made probably 8 or 9 trips since then where it ran fine all day.
 
riopga said:
Are there any tricks to removing the head covers? I am worried about broken bolts. Is sudden sharp jolts better than slow steady pressure? What about an impact driver? Heat?

I think I need to change the water deflectors. There seems to be an internittent overheat. Twice recently it seemed to run fine all day, but then as I came back to the dock and idled down the overheat alarm went off.

I did recently replace the entire water pump assembly, but I have made probably 8 or 9 trips since then where it ran fine all day.
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The head cover bolts are more likely to break than the head bolts. To replace the water deflectors I would not remove the head covers, just remove the heads with the covers left on. To remove stubborn bolts I would tilt the motor so gravity can assist a penetrating oil to soak in for a few hours. Then begin the removal by very slightly tightening the bolt before loosening. I would use steady pressure instead of a sharp jolt. Another technique that has proven helpful for me is rapping the bolt head with a hammer as well as applying heat with a propane torch. If the bolt is corroded enough it will break and will need to be extracted or drilled out and a helicoil insert installed.
 
I have lent my secret out on this before. Acetone 50/50 mixed fresh with auto transmission fluid. It should be a fresh mix. Mix only what you expect to use for the job. Phil's advice is good, I assume a saltwater exposed motor. It could need a flush with acid. Hydrochloric is commonly used. Seems funny, but calcium chloride mixed with water forms hydrochloric acid. That's why our cars and trucks rust away up here in the northland.
 
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