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1999 Johnson 115 Running Hot on Starboard Side

C

captainjeff

New member
Hi,

1999 Johnson 115 (60 Degree V4). I was running it in the driveway and noticed the starboard cylinder head and thermostat housing was hotter than the port side. I checked with a non-contact infrared thermometer and found the port side was running around 105-108 F and the starboard was running between 130-143 F (too hot to touch for long). The lower cylinders on each bank ran cooler than the upper. This is after running 5-10 minutes between 900-1,500 RPM on earmuffs.

There is a very strong telltale stream. I replaced the thermostats two years ago. The boat has been used 95% in freshwater. I just replaced the complete waterpump with an OEM pump kit but I don't think that has anything to do with it. This doesn't seem normal, please let me know your thoughts. Thanks!
 
Thanks Faztbullet, I think you hit the nail on the head. I swapped the thermostats from one side to the other and then the starboard side was running cool. I exercised the little metal plunger on the "bad" thermostat with a pocket knife blade. I noticed it has a slight rattle now when you shake it. I ran the boat again and now both thermostat housings are running in the mid 140's F. I am thinking it was just a stuck thermostat and the opposite bank was over cooling because this one didn't open and most cooling water got diverted to the other side. Any thoughts on this? Thanks :)
 
The stats are closed in non operation so if it was stuck and causing a cool bank, then it must have had some debris in it holding it stuck part way open.
 
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