Where's the water going?

[Don Crowther]

Hi
I'm trying to figure out where's the water going from my overflow tank. I have a 2 gmf. The level seems to drop after a couple of hrs. of motoring. So I refill it up to the marks and off we go for another couple of hrs. Now this isn't a big problem because I usually only run the engine for about 30-45 mins. each outting.
This is a closed system so do you think it might be the heat exchanger? Or worse a blown head gasket? The engine isn't overheating and I usually run it at 2800 rpm. I will be pulling the boat in a month for the winter and will be able to work on it over the winter.
As always thanks
Don

 

[kloudie1]

Could be the heat exchanger since at temperature, the coolant side is higher pressure than the raw water side.. I’d suspect the end cover gaskets first, and tubes, but it could be a bad head gasket as well. Generally, a bad head gasket will cause a lot of puffy white smoke for a short while after start-up.. Don’t try to re-use the heatex rubber gaskets.. For your engine the cover o-rings are 24311-000700, and the tube bundle gaskets are 128695-44070. You’ll need two of each.. Don’t overlook the overflow tube itself that connects the engine to the reservoir.. if it is old, it may be leaking .. A bad “radiator” cap on the engine can cause loss of coolant as well.. Look carefully at both gaskets in the cap, and the seating surface on the engine, just above where the coolant tube attaches to the heatex housing. You may be able to find an automotive place that can test the cap for sealing.

 

[Don Crowther]

Thanks Claude

I havn't seen any steam or white smoke coming out the exhaust. The elbow always feels cool to touch when the engine is running.
There doesn't appear to be any external leaks showing. If it was the end cover gaskets would it show up as an external leak? Could the tubes be letting water pass from one side to the other?
I was planning on removing the elbow and heat exchanger this fall when I pull her out for the winter. I've been reading that you can clean the tubes with a pipe cleaner. I will have the rad cap tested as well.

 

[kloudie1]

Yes, the OD of the rubber gasket gasket seals the seawater side from the coolant side. There'd be no external leak if coolant was leaking to the seawater side, it would be going out with the exhaust water. It wouldn't smoke because you'd not be burning the glycol A hole in a tube would act the same, but that is an expensive one! Your bundle part # is 128290-44400. The O-ring seals the cover from ambient air, so if it leaked, seawater would come out but there'd be no coolant loss; the o-rings should be replaced when the gasket is replaced. Good luck with it, Don

 

[jtm]

another place to look- if you have like a 2GM that has a branch off (at the top of the front engine) which takes preheated antifreeze to the electric water heater, then maybe you have a leak in that branch and/or in the water heater side. Hoses that go thru cutouts in the fiberglass do get eaten up over time by vibrations of the motor. Check the hoses all the way to the water heater. I "sleeve" with an extra slit hose the areas where hoses go thru cutouts.