Coolant in the exhaust when I started it. Got towed back to the mouth of the harbor. Was able to limp the boat back to the slip .

Don't think blown head gasket because I wouldn't have been able to limp back. So either elbow gasket or blown heat exchanger.

The overheating was gradual. Took 20 minutes for it to overheat.

What do you think?

Hung thermostat?

Got a pressure tester ? From my end coolant in the exhaust is never a good thing.Heat exchangers when they get warm can crack and when they crack coolant does leak into the exhaust.I see this on newer emissions diesel engines with EGR when they use coolant to cool the exhaust gasses before recirculating.I am not sure the purpose of a heat exchanger on a boat.I would take off the exhaust intake and exhaust outlet of the heat exchanger.Leave the coolant lines attached and pressurize the system.The water will leak out of the exchanger if it is the suspect.Not knowing the type of engine and configuration this diagnosis could be way off.I have also seen exchangers that wouldn't leak when they were cold but once warmed up would start leaking.I am not sure what an elbow gasket is on that engine.Maybe if your smelling coolant burning on your exhaust it could be a gasket above your manifolds like a t-stat gasket or elbow gasket.Sorry I couldn't be of much help.

Your're on the right track. Start simple. Riser, Riser gasket, heat exchanger.......Could still be the head gasket even thou gradual......

Assuming FW cooled exh manifold since you mentioned elbow gasket.

Hope it is not the exchanger, a bit pricey......

Got a pressure tester ? From my end coolant in the exhaust is never a good thing.Heat exchangers when they get warm can crack and when they crack coolant does leak into the exhaust.I see this on newer emissions diesel engines with EGR when they use coolant to cool the exhaust gasses before recirculating.I am not sure the purpose of a heat exchanger on a boat.I would take off the exhaust intake and exhaust outlet of the heat exchanger.Leave the coolant lines attached and pressurize the system.The water will leak out of the exchanger if it is the suspect.Not knowing the type of engine and configuration this diagnosis could be way off.I have also seen exchangers that wouldn't leak when they were cold but once warmed up would start leaking.I am not sure what an elbow gasket is on that engine.Maybe if your smelling coolant burning on your exhaust it could be a gasket above your manifolds like a t-stat gasket or elbow gasket.Sorry I couldn't be of much help.

Adam, your thinking all bassackwards....... heat exchanger has nothing to do with exhaust. Saltwater to Antifreeze

Stumbled across this while trying to figure out the purpose of risers.Interesting page.

Replacing Marine Manifolds and Risers – News and Information on Boating, Boat Repair and Boat Maintenance (http://www.boatpartsinfo.com/2010/05/replacing-marine-manifolds-and-risers/)

Oh yeah.. forgot to mention it's a FW cooled Mercruiser small block.

Adam, your thinking all bassackwards....... heat exchanger has nothing to do with exhaust. Saltwater to Antifreeze

I work on diesel engines and am not familiar with marine engines.I just did a little research.I wouldn't suspect the exchanger first.Seems like risers and manifolds have a short life span depending on the environment.When I see coolant in the exhaust of an EGR diesel it is usually the exchanger but this is a different animal.

The only positive to the whole day was it was a flat calm day 3 miles outside of Green Harbor catching macks.

Glad I wasn't on Wildcat in 3-6s.

For coolant to enter the exhaust it sounds to me like the heat exchanger could have rotted thru and is mixed cooling seawater with the antifreeze or you have a head gasket leak of some kind. If the engine is running smoothly then look to the HE. Did you winterize it properly? (Freezing water could crack the brazing inside)
Take it off and either take it apart or have it pressure tested/cleaned/boiled out. Do you keep a temp gun on board? They are really inexpensive and they help diagnose temp problems of all kinds. I keep one in my toolkit. You can measure the inlet and outlets of the HE and see if it is working OK. Also check a lot of other things without taking anything apart.

If the HE is compromised internally, you could be mixing coolant and seawater that will eventually exit out of the exhaust. If the engine is running smoothly otherwise, and you don't see any obvious problems I would look here first.
Best of luck. How hot did she get? Are you sure you have coolant in the exhaust? How much coolant did you loose?

Are you sure you have coolant in the exhaust? How much coolant did you loose?

Thats a good point, it could be just leaking out of the overflow if it was boiling and getting into the bilge....

When I started the engine, I noticed coolant in the water coming out of the exhaust before it overheated (a lot). That was a big "DUH" moment. I had been fishing all night at the canal and was delirious after 1 hr of sleep. I should never taken the boat out after seeing the coolant. (lesson learned) After I go outside of the jetty and ran for about two miles the engine went straight into the red hot on the temperature gauge and the warning alarm went off.

The engine was winterized properly by Jim at Coastal Marine in Marshfield.

I would suspect the heat exchanger 1st. With a fw cooling system if you are seeing that much antifreeze in the exhaust there has to be a hole in there somewhere. If it was a head gasket you would see a lot of white smoke in the exhaust and if the failure was bad enough chances are that cylinder wouldn't fire at all, and you would notice that.

You have a very similar engine to me sounds like. If you lost allot I would lean towards the HE. I had to do mine about 5 years ago. That is about 7-8 Marine Units. 1 MU = $100

On my MerCruiser HE there is no provision for an anode which is never good. When mine went I tried plugging a few tubes but it was more like half the tube sheet was leaking.

Make sure there's no water in the oil if the risers go they can let water down thru the head and Past the valves and into the oil.
Maybe the raw water pump Is junk causing it to overheat in the first place, and the antifreeze blowing out is the secondary problem?
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Andrew,
Sounds like a good reason to convince your dad into flipping the bill for a diesel re-power :uhuh:

Andrew,
Sounds like a good reason to convince your dad into flipping the bill for a diesel re-power :uhuh:

He pays for the slip. I bought the boat. He gets to use the boat when he wants. We split repair bills. A good partnership we have. I'd have a better chance of seeing god than getting him to pay for a diesel. :D

I brought the idea up of a diesel and my wife reminded me that we're supposed to be saving for college educations.

The heat exchanger was replaced yesterday. All is well with the world except I think I got ripped off on the part price.

Glad it worked out without replacing an engine.

Fox 25 news been in GH this morning.
Saw a few boats in know in the mooring field in the back ground.

I brought the idea up of a diesel and my wife reminded me that we're supposed to be saving for college educations.

Good for you !!!:uhuh:
The kids should come first.
An education is the best insurance in these days.
So they won't have to borrow from you for the rest of their lives !!!

You already have a nice boat too..

Between my wife's MS, and my 2 kids, I've been paying college tuitions for the past 11 years. This is the last year, and we just made the last payment. So the bigger boat is next. (maybe)....:biglaugh: She wants another house.:wall::wall:

Glad the repair worked out for you.