Are stock Merc thermostats designed to fail in the open position? I took the boat out this past weekend, and the port motor was very slow to warm up. In fact, it only got up to about 120 or so, and the starboard side reached 150 as normal.

BTW, the port side had good water flow out the exhaust.



Darrell.

Could be some debris in there holding it open. Just put in a new one.

I have had this problem twice on my current boat in 3 seasons, and once on a previous boat.It was always the Merc.
thermostat that wasnt closing all the way, either sticky or junk holding it open. One problem I had on my previous boat when one engine wasnt getting up to proper temp was a broken plastic water drain plug in the block of the engine. The water wouldnt stay in the block long enough to warm up and was getting dumped in my bilge, I noticed my auto bilge light on and my engine temp a little below normal. Rare problem but possible.

Thanks guys. I'll just put a new one in then, since I'll have to pull it apart anyways.





Darrell.