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Johnson overheating

1

16ftstriper

New member
Yesterday while out with my 1999 Johnson 50hp 2 stroke I accidentally got in some shallow water and had to run through some sand. After making it through a good amount of sand I headed back to the launch, and about 5 minutes later cruising back the overheating buzzer came on. I slowed the boat down to idle and let it cool and shut it off for a while. I limped it back to the launch and the water coming out the tell tale was warmer than normal.

Today I put in a new water pump, new thermostat, and flushed the entire engine. There was a lot of sand everywhere in the cooling passages but got it all out. I even pulled the water passage cover to flush it out. I took it out to test, and it never overheated, but it seemed like the water coming from the tell tale was warmer than normal. It is normally cold/slightly warm, while today it was pretty warm (not hot). It is shooting water out the tell tale better than it was before, but I am not sure why the water is warmer than before.

I think it could be blown head gaskets or an improperly installed thermostat, but I'm not sure. I did a compression test and it was exactly the same as it was a week ago, and the spark plugs look normal. Any advice would be appreciated!
 
The water coming from the tell tale was usually lukewarm at best. When the engine overheated yesterday the tell tale stream was hot, and now when it runs its very warm. I thought that would be a good indication of running a bit hotter for some reason?
 
Pull the exhaust cover..water goes thru this first, and if restricted it can pick up the heat and make pisser warm...
 
Agreed----There is a blockage and water is staying in the exhaust manifold area too long and the tell tale will get warmer.----Should be an easy fix.
 
Get yourself an infrared temp gun. Check for hot spots. Sand could still be trapped as aforementioned. I - guns are fun.....use them more than you think. I use for checking oil temp when I fry foods too. Motor should show 150 or less in most areas expected to be operating temp. Note: James meant to "heat it".
 
I pulled the thermostat, lower unit, and the water passage cover on the side of the engine that the tell tale stream comes from. I flushed it with a hose through the thermostat and any water passages I could. Is the exhaust cover something different than the water passage cover? Water seems to flow well everywhere I could see through the passages and the tell tale stream is very strong.

And I'll try to pick up a temp gun and check for hot spots, good idea.
 
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