PCM ZR 409 temp and overheating issue

[kauf391]

I just purchased a used 2011 Ski Nautique Open bow with the 409 engine with closed cooling. I am wondering what temp this engine is supposed to run? I think mine is running too hot (200 when idling and 175 when running at higher RPM's).

Also, where should I be looking with the closed cooling system to fix the issue? I've checked all the clamps, etc and haven't found any leaks. Antifreeze appears to be possibly disappearing, but not leaking. I'm not overly familiar with closed cooling systems (last boat has the Ex 330 and before that the GT-40).

Any guidance would be appreciated!

[vision]

Check the raw water impeller. Likely needs to be changed. Your findings are characteristic of lack of suction at lower rpms. Also, make sure strainer is clean and there are no obstruction of the intake thru hull on the bottom of the boat. Temps should be below 175 at all times.

[kauf391]

Thanks, it was just replaced. I've had this issue before on another Nautique and it was because the strainer gasket was missing. I've verified that everything is there and tight, how would i go about finding where the air may be coming in if it is on the raw water side?

[vision]

I would still double check the impeller as there was a bad batch of after market impellers. Replaced mine and had my boat over heat 10 hours later and the impeller was shredded.

There a few ways to check your system for vacuum leak in the raw water intake. I typically close the thru hull, pull the hose of the impeller housing and hook up a air pump (I use a portable wet dry vac as the tube fits in the hose to the impeller) and look for water being pushed out of the the various connections.

[kauf391]

thanks! Ill double check all of that again

[TRBenj]

I would recommend bleeding the cooling system, it sounds like you may have some air in there.

You can do this by removing the hex plug on the top of one manifold and then raising the coolant reservoir until fluid comes out the plug hole. Reinstall the hex before lowering the reservoir. Repeat on the other manifold.

Obviously make sure your fluid level is proper afterwards.