5.7 Merc coolant check?

[Wateronthebrain]

Ok, I sort of feel like a dork, but upon reviewing service manual over and over again, I can't figure out if my v8 is open or closed and how to check cooling system with regards to maintenance in general.
I don't have a heat exchanger or a degaussing/overflow tank. I am not overheating. But I just would like to figure out how to keep an eye on it.
I'm really not completely inept as I recently pulled and installed a new gimble bearing upon realizing a growing vibration while taking on gallons of water throughout the day must have been rusting the bearing as it was leaking from drive shaft via ujoint bellows. When in water test all was smooth and quite again. When trailered, I pulled the plug and not a drop of water came out of the bildge! Couldn't believe I was successful!
Anyway, if anyone could direct me re:coolant check, I would appreciate it!
Scott

 

[saaristo]

If you don"t have heat exchanger it is open...meaning seawater cooled. There is no coolant to check.

 

[tpenfield]

Yes, sounds like an open cooling, aka raw water cooling, aka sea water cooling. No 'coolant' involved.

You can post a picture of the engine for verification . . . the heat exchanger (if there was one) and the associated hoses are hard to miss.

Are you in a region that gets cold (freezing temperatures) during the winter months? If so, the way you take care of the engine is 'winterization'. Several methods, involving either Marine anti-freeze, draining or both.

As far as taking care of the cooling system . . .
Be mindful of:
- Impeller
- Seepage/leaks around the recirculating pump, and exhaust manifolds/risers
- Keep an eye on the temperature gauge for any changes

 

[Lou C]

Also keep in mind that these are high volume low pressure cooling systems; they depend on a large quantity of incoming cooling water to carry away the heat from the engine & exhaust system. The impeller in the outdrive or on the engine pulls water in and then the thermostat housing directs it to the exhaust system where it cools the exhaust & then exits overboard. After the engine thermostat opens it allows hot water to exit the engine which then mixes with the incoming cool water and exits via the exhaust system. So basically that’s how it works. Impellers are a wear item they need to be replaced every 3 or so seasons; in salt water thermostats start to get sticky and exhaust elbows start to clog with rust after 5-7 seasons or so. In fresh water not so much. The front circulating pump bearing & seal eventually wear & make noise & leak. These are cheap & easy to replace.
Each season go over all the hose clamps make sure all are tight & there are no leaks,
and watch for leaks between the exhaust manifold & exhaust elbow. If you see that’s it’s a sign that it’s time to take the elbows off for inspection. This is especially true if you have wet joint exhaust (Merc prior to 2002, all Volvo & OMC). In salt water my present boat has had the exhaust replaced 3 times in 20 years. Impellers every 3, the thermostat whenever it gets sticky (doesn’t close all the way or open all the way) and the front circulating pump when it starts to make noise. The hoses seem to last a very long time but replace when they get hard & stiff.

 

[poconojoe]

Learn how to replace your impeller as suggested.
Really bad things can happen to these engines if you overheat.
Replacing the impeller is cheap insurance that you are getting a good water supply to the engine.

 

[Lou C]

yep overheats can blow head gaskets, & and can crack cylinder heads, leading to a pretty extensive repair...
people new to boats don't realize its not like a car, with a closed low-maintenance system, in a boat you need a constant supply of cool water in and out, for it to stay at proper temps. Your impeller pulls it IN, your thermostat and exhaust system allow it to get OUT....
don't wanna wind up doing this do ya lol?

 

[Wateronthebrain]

Yes! I was thinking it was the open raw water system that was employed on my boat...but now I know for sure. She runs at like 140° consistently so I'm great full for the clearity!
Thank you to each and everyone of you here to take the time and consideration to reply here.
Yes, I have changed the thermostat and impeller as well this year along with rebuilding my Rochester 4 barrel along with that gimble bearing...
You and others here have greatly helped me with these processes.
Wow, why couldn't the world share a "peace" forum similar to It boats where together we all could work it all out? That would be awesome!

"...run to the rescue with love, and peace will follow..."
Scott