1975 Johnson 85 Overheating

[L.A. Sailor]

Hello,

I just bought my first powerboat (1975 Glastron V156) with a Johnson 85, model 85ESL75.

I started it up and it was not pissing water and it was overheating. I really wasn't interested in doing the repair myself so I took it to a local shop. Without hesitation (or testing), they said this happens a lot and it was the impeller. After replacing the impeller (which did need replacing) the motor was still overheating. The bottom end was staying cool but the powerhead was still getting hot. The shop said they think it could be a clogged waterline or exhaust and the powerhead needs to removed.

Due to some other circumstances I have removed the boat from the shop and am now looking to either finish the repair myself (I have the Service Manual) or at least be armed with some knowledge when I take it to a new shop.

Has any one encountered this type of overheating or other problems like this beyond the impeller? Are there any tests I can run to localize where the water is not passing through?

Thanks, Mitch

 

[ezeke]

Re: 1975 Johnson 85 Overheating

There is only one thermostat and it is a 105 degree vernatherm. If the area around it gets stopped, the water won't flow properly. Look at the inside bottom of each cylinder head and you will see the two hoses leading to the thermostat housing.

If you feel like tackling the thermostat, you have to remove the housing to replace or check it.

 

[bigbob_FTW]

Re: 1975 Johnson 85 Overheating

check the thermo first. Also on mine, the water jackets on the back of the cylinder heads were blocked with old sand and stuff. Cleaning these helped a bunch. Your getting nothing from the exhaust relief in the back of the motor?

 

[78big10]

Re: 1975 Johnson 85 Overheating

my 75 85hp evinrue did same thing it was a pluged thermostat took it out flushed with garden hose put same thermostat back in runs very cool now took about hour