PCM 343 overheating

[dtm]

I have a 2012 SN200 and have noticed the engine temp getting @ 200 degrees when started and let idling to warm up. If I rev the engine the temp drops to @ 175. Anyone have an idea of possible cause? Impeller is good, strainer is clean. Thanks,

[s_kelley2000]

I am guessing your boat is raw water cooled? I have heard the fresh water ones run a little hotter but if it's raw water cooled then even that 175 seems high. A raw water cooled boat should be right around 160 degrees. The first thing I would check is the rubber gasket on the water strainer. Make sure it is seated correctly and still in good shape. If that is not on right it will let air into the system and cause it to run hotter, especially at idle. Check all hose connections to make sure they are tight as those could allow air into the system as well. If none of those do it then it could be your impeller starting to go out on you.

[Quinner]

Assuming a raw water, not closed loop:
Remove and inspect the impeller & strainer, re install confirming all rubber gaskets are in place, tighten all intake water hose clamps using a nut driver.

Sounds like you could be sucking some air, do the above and then take a test run.

[dtm]

It is raw water cooled. I've recently had the strainer and impeller housing apart. I think they are good, but will check again.

[perry386]

Could be the serpentine belt as well. If it's getting hot at idle and then cooling off when you get going, the belt may be slipping while at idle and then when you hit the gas it could be grabbing back on and turning the impeller. Just a thought because my belt was doing that one day and we decided not to worry about it...then mid-set the belt completely snapped and we were stranded.

[wskiboy]

check your rubber gasket on the strainer

[Nordicron]

Yeah I agree your sucking air in somewhere between your through hull and raw water pump.

[dtm]

Thanks for the input. I went through the supply line to the pump, tightening clamps, and checked the rubber o-ring on strainer. Put some plumbers' grease on the o-ring and seemed to have it fixed.....BUT, it overheated again yesterday at idle. I've noticed that the overheating seems to correlate with a "Whirring" noise from the raw water pump. The noise will start and then the temp will begin to rise. Can't get it to do it all the time, just intermittently.
-Anyone know what this whirring noise is caused by?

[shawndoggy]

I recall that there was a bad batch of engine water pumps on 2012 5.7L gm blocks. Can't find the cite for it right now though. It was the engine water pump, not the raw water pump that was the problem.

Have you checked the gasket on the raw water pump to make sure you aren't losing prime?

[swc5150]

It sounds like you double checked the really easy stuff. I'd now let the warranty do it's thing and drop it off at the dealership for service.

[brianc]

Check the water drain on the inline oil cooler is not loose as may be drawing air in there your obviously getting water flow so it not fallen out

[HS]

Unlikely but I wanted to respond: when you described a whirring noise, it made me think the impeller might be "spun" (worn) and that it is slipping on the pump -- kind of like how a ballast impeller can get worn, but thos impellers lack the metal reinforcing found on the PCM water pump impellers, or so I thought . . .

Also, could it be a sticky T-stat?

[Nautiques_NZ]

I would be looking at the circulation pump, had one the other day that had completely broken in half internally, same issues. Hot at idle, ok up to about 28mph and then hot again.

[NickJV1]

Did you ever find out what the problem is? I have the PCM ZR 409 engine. It only overheats when I take it over 3500 RPM's, and when it idles. Turning the boat off does not help, it actually makes it worse. Two different mechanics cannot figure it out. Any suggestions/advice would be very much appreciated.

[dtm]

I thought I had it fixed, but I still experience the overheat at prolonged idle...every so often. I took the raw water pump apart, inspected the impeller, then reassembled using a plumbers grease on the o-rings. It seemed to fix it, but the symptoms returned after a couple of outings. It definitely seems as if the problem is with air being sucked into the line, but I haven't been able to solve it completely. Mine only overheats at idle. Upon revving the engine the temp will drop below normal, then settle in. The "whirring" noise happens consistently, right before the temp gradually climbs.
Thanks for all the input!