We had been getting a lot of water in the bilge while underway under power. I know we have a leaky stuffing box (another project) but I never quite believed that could be the cause of all this water. When running the engine, the bilge pump would expel water for a few seconds about every minute!
On Saturday, while Linda was driving (with no wind), I went down to look for the source. Opening the engine compartment, I could see that water was pouring out of the radiator overflow tube. Worse, it tasted salty. Since our engine is not a magical water maker, the obvious reason is that raw water is crossing the boundary of the heat exchanger. So we've effectively been cooling the engine with salt water all season. Not good.
I googled around and found a few forum posts talking about this exact problem. I have never even seen a heat exchanger before but I got some edumakation on them. In case I couldn't get to it (or more likely it was over my head), we opened a work order with the marina to have it looked at.
Let me try this
I printed the entire PDF of the shop manual for the MD2030 and also a few exploded diagrams I found. I also read and reread the forum threads on the topic. Most likely, the seals on one end or the other are not tight or the worst case is that holes have corroded in it and it's leaking. If it's the latter, the part is about $650 or more.
Step 1:
Get the exchanger out. Right away, I realized that the cabinetry around our engine was not going to make this simple. I had to remove the front surface of the engine compartment that has the door in it. While I was futzing with that, I drained the "coolant" (actually brine) out of the engine. Also CLOSE THE THRU-HULL for the raw water if you like the boat to stay on top of the water.
To remove it is pretty simple. Actually the whole thing is pretty simple. You just undo the hose clamps on either end of the exchanger housing, remove the front boot from the housing and slide the whole unit out. It's a cylinder about 2.5" in diameter and about a foot long.
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| Exchanger housing with the exchanger assembly removed |
Look at it and marvel at it's simplicity. Now look at how disgustingly filthy the thing is and how clogged all the tubes are.
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| After the first flushing with the hose. Yuk |
I put it in a bucket and carried it over to the dock. DON'T DROP IT IN THE WATER. DO NOT DROP IT IN THE WATER. It would be very easy to imagine this thing rolling off the dock - splash - $650.
Step 3:
Clean it and figure out if it has a leak. Blast the crap out of it with as much garden hose pressure as you can get. Marvel at the crud in it. At first, I didn't realize you were supposed to be able to SEE through the little tubes in it (I couldn't but you are).
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| almost like new. No more debris coming out. |
After a few more flushings with no more crap coming out (hey look - you can see through all these tubes!), I tried pouring water slowly though the tubes to see if any was leaking out the fresh water holes. Nothing! This is good! The unit actually looks pretty good now that it's clean.
Step whatever:
Put it back together. I took the garden hose in the boat with me and really blasted out as much more crud as I could in the housing. I also really cleaned the rubber boots that seal the ends of the exchanger. Slide the exchanger back in the housing and tighten the hose clamps on the boots.
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| Exchanger housing with the clean exchanger re-inserted |
Next step:
Refill the engine with actual coolant. As much as I enjoyed the brine cooling design, I hear good things about this coolant stuff. Oh and don't forget to close the drain cock when you pour your nice new coolant and fresh water in the engine.
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| All re-assembled. ready to fill with actual "coolant" |
Did it work?
Fire up the engine. OPEN the raw water thru-hull first. Hey it runs. Hey raw water is flowing out the exhaust. Hey look NO raw water is flowing out of the radiator overflow tube! I'll run the engine for a while before I call it a success. So far so good
I'm thinking now might be a good time to buy various cooling system additives.
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