318 TStat problem

"I installed new 160f thermost

"I installed new 160f thermostats this year on my twin 318s. At idle the stbd engine sits @ 160+ then jumps to 200f when the tstat opens,then the temp drops back down and this keeps repeating. The port engine idles below 160f. Both run very similar temp when cruising above 2k rpm. Any thoughs why the stbd temp is erratic @ idle?"

I would check the impeller on

I would check the impeller on the raw water pump. Also check for air leaks on the suction side of the pump.

"You might have a bad, new t-s

"You might have a bad, new t-stat. It happens.

Jeff"

"FWC engines, raw water flow g

"FWC engines, raw water flow good and good psi test on fresh side. The current t-stat is the second this year, first was letting temp get to 220-240 before it opened while this second unit opens around 200, neither would hold 160f at idle. Any thoughts on the different engine water pump rotation(s)possibly causing this problem?"

"Dan,
What is happening to yo

"Dan,
What is happening to you is sooooo frustrating. It happened to me recently,see earlier posts, same symptoms. I removed tested re installed and replaced thermostat over and over. Tightened all hoses etc as I thought it might be air pockets.

Recently I pulled the raw water pump off just because I thought it was time to check the impeller and bearings, all were good,re assembled pump with a little grease on the impeller blades, re installed pump on motor, and all my overheat problems went away.

I don't know what it was, maybe sucking a bit of air into impeller housing or whatever, but the problem went away, and the thermostat is behaving as it should.

I can only suggest that you check the pump out and all the hose connections, as I think your problem may be associated with the raw water pump pulling air into the heat exchanger.

Just my 2 cents worth. Good Luck.

Ray."

Check the strainer to make sur

Check the strainer to make sure the lid is not letting air in.

Jeff

Thanks for the info. I had no

Thanks for the info. I had not thought about air getting into the system only raw water flow slowing/stopping.

I was plannning on replacing the raw water pump this winter as the bearings are groaning/whining and the housing is rusted/dripping water.

I'll reply in the spring with either more questions or with that second T-stat I bought for sale.

Sounds like that raw water pum

Sounds like that raw water pump may have been the culprit.

Jeff