81 Johnson - lots of questions overheat?

[jmanajb]

Hello, I have a 1981 90 Johnson. After a rebuilt power head, new t-stats, impeller, etc. It seems I have a water leak between the power head and base of the motor ( is this called the exhaust gasket?). Will this cause problems? I have noticed that one side of the motor gets hotter than the other with the muffs on. I took the water hose off at the t-stat housing... cooled right down. Could the gasket leak be causing this? Do I need to run at high RPMs on the lake to get the right flow through the t-stats or get them to open? One other bit of info - this engine was mothballed to two seasons after the rebuild and break in - Thanks for any help

 

[rodbolt]

Re: 81 Johnson - lots of questions overheat?

any water leak between the powerhead and powerhead adapter must be corrected before further testing.<br />what t-stats did you use and what sealer was used on the t-stat housing?

 

[emdsapmgr]

Re: 81 Johnson - lots of questions overheat?

At one point, OMC used a paper gasket between the block and the exhaust adapter. The paper gasket tended to fail quickly. It has been superceded to a new gasket which is much more substantial and will last longer (342513.) Make sure you get the right one. As mentioned, you will need to replace this before further use. Also, the valve body in the thermostat housing has two very small holes. If either plugs up, that side of the block will overheat. Make sure they are both open.

 

[jmanajb]

Re: 81 Johnson - lots of questions overheat?

Rodbolt, No sealer on the t-stat housing<br />T-stats PN 434841 (2)<br />T-stat cover gaskets PN 332369 (2)<br />I took this engine through a number hours for break in after the rebuild. No issues except for this leak. Now after removing from storage, this wierd one side warmer than the other. on the p-head. I can hold my hand on it for at 3-5 seconds but would not want to go further than that. Will that gasket failure reck something? The bottom of the p-head is sealed. Thanks!