Checking thrermostat on 1972 Johnson 85

[carmangary1]

Is it possible to check the thermostat on a 1972 Johnson 85 without removing the powerhead? I don't know if it has ever been replaced or what kind of shape. Should I even bother?

 

[DJ]

Re: Checking thrermostat on 1972 Johnson 85

carman,<br /><br />The thermostat housing is at the back of the engine, between the two banks of cylinders. Two rubber hoses go to housing from the cylinder heads.<br /><br />You can remove it without removing the powerhead, but it's a bit tedious.

 

[ledgefinder]

Re: Checking thrermostat on 1972 Johnson 85

The thermostat should open at 145 degrees F. You should be able to rest your finger on the body of the cylinders without getting burned, but it should be fairly HOT. On an OMC with a good thermostat, I can rest them there for about 2 seconds. If it's a lot cooler than that, either they're stuck or someone's pulled them out. Opinions differ on whether running without them is OK. You'll idle worse, some feel you'll wear the motor quicker. On the other hand, Mercs ran without them until the mid1-1980s & I know two long-time mechanics who routinely pull them out of older OMCs figuring it's better to be too cool than to take the chance of it sticking closed.