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AQ151A Thermostat

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laissez_faire

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"I recently purchased a boat w

"I recently purchased a boat with a 1986 AQ151A (motor with a heat exchanger). The previous owner said that for each of the past couple years the motor ran slightly hotter, by perhaps a few degrees each year. He believed the thermostat needed to be replaced. Right before I purchased the boat, he removed the original thermostat and went to a local marina to get a replacement. He claims he was told that he didn't need to replace the thermostat and that the motor would run fine without it. I believe this is an 82 degrees Celcius thermostat.

After searching the message board, I've noticed that running with/without the thermostat is a debated topic.

Assuming that the thermostat is in fact the cause of the elevated operating temperature, I'd appreciate comments on running with/without a thermostat."
 
"First, replace the thermostat

"First, replace the thermostat if you have removed it. Not only is necessary for the engine to run efficiently, but being a fresh water cooled engine the thermostat is seldom a problem.

Second, if the engine runs hot, check:

1) The raw water hose connector between the outdrive and the transom shield. If it is corroded/perforated, the raw water pump will suck air. If you search the forum you will see this a very common problem which has an easy and cheap solution (around 30 bucks).

2) The pump impeller.

3) The raw water strainer.

4) The oil cooler (make sure it is not clogged).

5) The exhaust manifold. Make sure it is not plugged with mud, etc at the bottom where the water copper tube is attached; and also make sure the riser part is not corroded/plugged-up with scale (if this is the case, get a new manifold)."
 
Thanks for the response El. I

Thanks for the response El. I already noted your five point checklist in previous threads. I'll be sure to post an update after checking everything out this weekend.
 
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