generator heat exchanger?

mnm99

mnm99

Well-Known Member
Oct 2, 2015
2,447
Long Island
Boat Info
2004 340 SeaRay Sundancer
Engines
Twin 8.1 Merc
I just winterized my Kholer generator and noticed a small spot of corrosion through the paint on the exchanger. It looked a little powder like. I'm concerned about the the exchanger going bad and ruining the engine. What is a good way to check? It's not like the end caps can come off. In the pic is where I have the spot. I;ll take a pic today. Some history..It has 35hrs on it, Fresh water it's whole like except the last 3. I flush it with fresh water EVERY time I come back to the dock.
39134b_1_1.jpg
 
35 hours on the generator, or 35 hours on the heat exchanger? For many of us the generator is mission critical - can’t leave the dock without it. But if you only run it 2 hours per year, let it go. The failure won’t hurt the genset, just cause it to shut down. Check it periodically and replace it if it starts to leak.

I don’t think fresh water flushing is necessary either.
 
35 hours on both. Now that I think about it you're right. There aren't any oil coolers or transmission coolers that if the heat exchanger went bad would cause the mixture of fluids. I was thinking along those lines. Worst case scenario the antifreeze would mix. Thanks
 
But if the internal tubes corrode thru, you will be mixing seawater with engine coolant. I had that happen.....when my original heat exchanger had 1500 hours at 21 years service age in warm Florida water ! Just keep an eye on the coolantn and when it looks like rust soup, raise the red flag.

I think you are seeing a spot of surface corrosion on the exterior of the heat exchanger which no cause for alarm. All that takes is a pin hole or scratch in the paint to get a sopt of corrosion to begin. Sand the corrosion to bare metal and spot paint it. I took some samples to an auto paint store and got a quart of acrylic enamel mixed for both the main engine color and my generator color. For larger touch ups, I use a Preval sprayer, for smaller ones, an artists brush. Stay after the corrosion spots and you boat will look new when you are ready to trade up or sell it.
 
Mike, from what you have stated, it sounds like superficial corrosion. Certainly nothing to worry about to the extent you posted. This exact thing happens with sterndrives/outboards in fresh water. A small crack or pinhole develops in the paint for some reason... could be a speck of dirt on the metal before it was painted and the paint didn't adhere properly... could be just expansion/contraction and the paint opened up. But the result is exactly what you describe - a little powdery like corrosion. Sand it back to clean metal and repaint. Take care of it now, while it's easy - before it gets bigger - but, realistically, whether you do it now or in the Spring doesn't really matter. Put a dab any kind of paint on it for now, if you really want to.
 
juggernaut1 said:
I don't think freshwater flushing is necessary either as you have a pencil annode in the exchanger don't you?
Click to expand...
How often do you need to change the pencil anode on the gen? Mine is fresh water but I don't think its ever been changed and I have 1200 hrs on a 2003 yr.
 
I'm in salt and find it needs changing every 6 months. I've tried 12 months but find there's virtually nothing left. The other problem is the annode can snap off in the exchanger when you go to remove them if left for too long.
 
juggernaut1 said:
I'm in salt and find it needs changing every 6 months. I've tried 12 months but find there's virtually nothing left. The other problem is the annode can snap off in the exchanger when you go to remove them if left for too long.
Click to expand...
Is it an easy change? Do you lose coolant when changing it out?
 
No loss of coolant because the annode is on the seawter side. Yes, very easy to change - probably one of the easiest things to do on your boat.
 
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