Johnson overheating

[16ftstriper]

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!

 

[F_R]

Somebody will correct me if I am wrong, but the water coming from the tell-tale is bled off before it goes through the powerhead.

 

[16ftstriper]

Somebody will correct me if I am wrong, but the water coming from the tell-tale is bled off before it goes through the powerhead.

I've heard this too, but when it overheated the water coming out was very hot, and before it was always cool. Now it's pretty warm. That seems like an indication of engine temp to me.

 

[ezbtr]

wear looser pants! I couldn't resist!!

 

[oldboat1]

If the water passage cover on the port side of the block is hot, the tell tale water temp would likely be the same temp or similar (elbow comes off the top of the passage). If you haven't done so already, it would be a good idea to pull the cover and check for warpage on a flat surface, clean out any sand that showed up since you cleaned it last, and replace the cover with a fresh gasket if needed.

If you run in sand or silt, your impeller probably needs to be changed annually -- maybe twice a year.

 

[16ftstriper]

If the water passage cover on the port side of the block is hot, the tell tale water temp would likely be the same temp or similar (elbow comes off the top of the passage). If you haven't done so already, it would be a good idea to pull the cover and check for warpage on a flat surface, clean out any sand that showed up since you cleaned it last, and replace the cover with a fresh gasket if needed.

If you run in sand or silt, your impeller probably needs to be changed annually -- maybe twice a year.

I pulled the cover yesterday and cleaned it out at the same time that I changed the impeller and the thermostat. It didn't seem warped and didn't leak. I did put a new gasket on it too. The water coming out was never as hot as it is now