Dangerous Overheat?

[brianontheroad]

So I already fried my engine or maybe I did -- but I know it dangerously overheated.

I was motoring back in from a great sail when I saw a faint bit of steam/smoke coming up from the engine area and immediately turned off the engine, the steam/smoke immediately got much worse, I'm glad I turned it off immediately but I'm worried I might have run done some damage, it smelled like burning coolant I think and today in my troubleshooting/investigating I found:

1. Impeller was totally eaten (could have been the cause of the overheat, or the result)
2. Sea **** was open, I tested it today and waters come out of it, though I'm not sure if enough is coming out -- it was like a garden hose without any sort of end on it (and this is after the strainer) a steady stream but not exactly powerful
3. I can't get my strainer open? I've never opened it before (only had the boat for 8 weeks, and had the engine checked out before I sailed it the 80 miles from Hilton Head up to Charleston) it looks like a standard old style strainer, like the top should twist off and then the strainer lift out? I must be missing something
4. The zinc on the heat exchange was totally eaten, but it also looks like the zinc is still in the heat exchanger? I'm not sure if it's corroded -- picture to follow, how do I get the zinc out to put a new one in?
5. I couldn't get the end of the heat exchange off to check for clogs, I was able to get the bolt off the end but not the cap -- do I just need to dig into it and give it some force or ?
6. The top of the coolant recovery tank was blown off (eek...bad sign) how did that happen? The coolant burning up?

The motor was only running for a few minutes total, but I know a few minutes can be a few minutes too long -- I'm going to replace the impeller with another Johnson 810, check the strainer (once I get the damn thing open) and the zinc.

What kind of coolant should I use? Do I need to flush the cooling system? Once I replace the impeller/zinc/coolant/check heat exchanger should I start it and see how it runs or are there other things I should check after a dangerous overheat? Any tips for a newbie to tell just how bad he f'ed up?

Thanks for all your help and advice.......

Brian

[sailingdog]

Brian-

It would really help if you said what kind of boat and engine you had. Some engines are more tolerant than others... and some have known issues.

BTW, you really should read the post in my signature...since it has a lot of information that will help you get the most out of sailnet.

[brianontheroad]

Westerbeke 27

[phallo153]

Looks like you already found the problem - no impeller (I assume you meant on the raw water pump) means no cooling in the heat exchanger. Overheating caused a rise in pressure which is what blew the top off the recovery tank. You should have heard an alarm or seem the temp gauge shoot up before you saw steam - do you have an operable temp gauge/alarm? You may have a faulty temp-sender.

Your strainer probably has some sort of cam lock on it, look for a long bolt that swings up into the strainer top and is secured by a wingnut, or something similar. That would be to keep a simpler cap from working it way loose.

Might be easier to service the heat exchanger by removing it completely. There are probably 4 hose connections (2x raw water, 2x coolant) plus whatever is holding it in place. On mine, the zinc is screwed into the bottom of the exchanger. The end cap is probably sealed, it will come off with some effort. I'd recommend just removing the whole contraption and taking to a radiator shop for servicing. $50 got mine flushed, pressure tested, a new gasket/sealant on the end cap, and a paint job.

You'll definitely want to flush the system to remove any pieces of impellar, especially between the pump and the heat exchanger.

[brianontheroad]

no alarm on the temp guage (I'll be adding one of those)

but the last recorded temperature was over 200 degrees, but less than 240

[brianontheroad]

This is my heat exchange with the zinc anode taken off, the zinc is like a bolt basically and it was broken off of the end, but it looks like its filling the hole (or maybe corrosion is.....) any thoughts on how to get that out

and you can see where I removed the bolt from the end of the exchanger....now I just need to figure out how to get the rest of it off!

great call on taking it off and taking it to a radiator shop....hopefully I'll be so lucky with the $50!

[brianontheroad]

hmmm image didn't show up...

here's a link

Picasa Web Albums - Brian - Boat Stuff

sailnet is awesome......thanks for all the input folks

[hellosailor]

Brian-
What SD said. Some engines are known to be robust, others damage easily. One thing that you can do is either grab the flywheel or put a wrench on it (or use a hand crank if you have one) and try to turn the engine over, slowly, with all power and fuel off. Open the decompression lever too, if this is a diesel.
If the engine turns easily and smoothly, you probably don't have damage. With modern engine oils, engines don't seize up as quickly as they used to. (Oil cools the pistons, then the coolant cools the cylinder walls and the block. But oil is actually the critical front-line cooling agent in the cylinders.)

Sounds like you really need a manual for your engine and your installation--don't scrimp on that! When you've got a used boat, you never know what the previous owners did or didn't do, like not change impellers. Do that annually as preventive maintenance, because once a fin breaks off the impeller, it goes on to clog the heat exchanger coils or the engine passages.

Ditto on internal zincs, you don't know if the previous owners "lost" an old one in the system and then added a new one, or if the correct one is in there. Far easier to get a manual, and see what is correct.

On the strainer, if it hasn't been opened in a long time it may be seized. Could be a gorilla put it on too tight, could be galvanic corrosion, could be six dozen barnacles glues it shut from the inside. Do your best to open it, but expect that you may need to replace it. And if it does open--consider using some teflon tape, pipe dope, or other lubricant on the threads when you close it up again.

On the seacock...how much flow depends on many things. Can you see through it? Can you poke a finger (carefully) through it? If the seacock is not obstructed, the flow is probably correct for whatever it is. If there is a strainer on the outside of that seacock intake--expect it to be full of barnacles, the strainer cover needs to be taken off the hull and cleaned from time to time (usually during hauls) and needs to be painted, inside and out, with bottom paint to prevent their regrowth.

Coolant? Generally a 50-50 mix of coolant and DISTILLED water. Minerals in "really good" tap water can damage a heat exchanged ten years down the line. using distilled water or deionized water at $2/gallon is a good investment in preventing that. A 50-50 mix will not cool the engine as well as a 60-40 (60of water) mix, but will protect it better against cold and heat. Again, your factory manual would be specific about that. The new "orange" permanent antifreezes are really great--but can't be mixed with the old green ones, you need to flush out the old coolant before using the new stuff. Also avoid the "antileak" fluids unless you are leaking, they also reduce cooling capacity.

And the blown off cap on the coolant recovery bottle? No mystery, if the coolant overheated fast, it would rise up, overfill the bottle, and blow the cap off. That probably means the pressure cap on your heat exchanger is working correctly--but if you don't know how old it is, replace it with the correct cap for that boat anyway. Make sure the seat is clean so the cap seals well, too.

But you'd really get better help faster, if you said what kind of engine and what kind of boat you have.

[camaraderie]

Brian....Phallo gives good advice above.
The only other thing I would add is to make sure your intake line is totally clear and without obstruction. You will need to dive on the through hull with a very long screwdriver or similar piece ofmetal to clear any barnacles, kelp, plastic bags etc that may be restricting your flow a bit without blocking it. Also...you indicate your strainer may be an issue.
From your description I assume you have something like this:
with a small plastic body and scre on clear cover for the cleanable mesh filter. Correct?
Suggest you get a Perko or similar like this:

I wouldn't worry too much about the engine since YOU were the one to shut it down and NOT the overheating. Your chances for no damage are very good!

[brianontheroad]

Thanks HelloSailor.......It's a Westerbeke 27 and the boat is a Chris Craft Apache

I have the manual (downloaded off Westerbeke.com.....thank god for the internet) and it recommends a 50/50 mix, thanks for the advice on the coolant, it was the orange coolant -- so that's good, I checked the oil today and it was full so hopefully that helped prevent any permanent damage