2003 Merc. 496 MAG - coolant low - any thoughts?

[trdehmer]

I was down in the engine compartment today and noticed the coolant was a little low. It was topped off about 1 month ago and I notice now that its a little low. I couldn't see any signs of it in the bilge - any idea where it would be going?

The 496 MAG is a closed cooling system.

The boat always seems to run at 170F once the engine is warmed up...

 

[trdehmer]

Anyone?

 

[skibum]

I'd start off by having someone check out your heat exchanger. The engine coolant circulates through small tubes in the exchanger which are surrounded by seawater moving through the "canister". If one of the small tubes has a hole in it, then your coolant might be getting pumped out of the exchanger with the seawater.

 

[fc3]

I've had a problem with port engine loosing a tiny bit of coolant over the summer. Never could find the stuff in the bilge. Put the cooling system tester on the heat exchanger and it held 16 PSI overnight. Finally found the problem this weekend. The coolant recovery tank leaks. Must have been a very slow leak that now has gotten worse so that it is finally visible. Pulled the tank and it's obvious that there is a thin spot in the tank. Pulled the tank from the other engine and it's thin in the same location. Figures that Mercury can't even make a decent plastic bottle.

Best regards,
Frank