Heat Exchanger

[Ip485]

I am tempted to give my heat exchanger a clean on my 100HP turbo Yanmar.

The reason is that only at the very top end of the revs I get a high temp alarm after a short while. I suspect this maybe because the exchanger is no longer functioning quite as well as it could.

The other possibilities are the sea water filter is partially blocked (checked that, all fine), the impeller is damaged, (havent checked that yet, but was replaced very recently) or the thermostat is faulty (also not yet checked) - unless anyone can think of anything else!

As I say the temp warning only comes on running the engine at full throttle (3,500 rpm) and is absolutely fine at 2,500 and up to 3,000 rpm for long periods which is the normal cruising range, and stops immediately after throttling back.

Yanmar say the engine will run fine at full throttle and indeed this should be done occasionally. As I mentioned earlier I am more worried that it might be an indication that the heat exchanger is not working as efficiently as it should and it may gradually get worse.

So, my second question is whether to remove the heat exchanger for a visual examination and clean or use one of the magic descalers - and if so which one?

The third question is if I do remove the heat exchanger what is involved as I have not done this before and thoughts on how best to clean once removed?

Thank you

[sailah]

I don't have a Yanmar but I vote to remove it.

On my boat, I get this crazy salt precipitation that necks down the inlet of my HX, and since it happens essentially from my water pump to exactly where the hose enters my engine, it's really not engine specific either.

When I bought the boat I noticed temps would start climbing when I was hard on it for extended periods. Still pumping good water, everything else you checked off was fine, new impeller, clean intake. 2 years ago I removed heat exchanger and was shocked how closed the inlet had become. Think clogged artery. My inlet hose was 1" and it had to be 75% blocked. Scraped out and cleaned HX.

So last season (1 year after removing) I figured how clogged could it be, well it wasn't nearly as bad but still enough it's now on my list every year.

I think this year I plan to use Salt Away and pump it through the system before laying the boat up. I like that whole idea and I think it would probably keep my severe clogging to a minimum.

But in your case I'd remove and clean really well, makes sure you don't have any impeller blades stuck in there. Going forward you can probably get away with a Salt Away flush. Heck maybe try that first before you disassemble not sure how difficult it is on Yanmar, on mine it's straight forward.

[Captsteve53]

Some thing to consider?

1) Has this always happened or a new occurrence?
2) How old is the engine?
3) Raw Water impellers need changing every year/season if you dont want these situations
4) It could be that the engine is just overloaded (wrong pitch prop size/dirty prop/hull)
5) Blockage in the exhaust riser (either rust/carbon or in the actual water inlet nipple as these often corrode and limit the amount of passing water
6) Heat exchangers may need cleaning but you normally need new gaskets /seals etc and often a **** fight to remove
7) When did you last change your coolant (max 2 years- other wise can turn into acid)
8) Salt A Way is great: Salt-Away Home Page

Cheers Steve

[Lepke]

You could have rust on the coolant side of the cylinders or in the head, insulating them and keeping them from being properly cooled.
I use Rydlyme on 2 mains and 2 generators for several years. And other engines before that. All with good results and no problems. You can dump it over the side or down sewers. I use 2 different methods. One with a pump and bucket. And the other with the engine idling using the engine's salt water pump and a big bucket. The hot method works quicker and cleans better & faster but you have to watch for over heat. It doesn't hurt the impellers or other rubber seals or parts. I occasionally use Rydlyme in the coolant side as it does a good job on rust. I have used it in friends' engines after the "local mechanic" flushed the system with something else, but didn't achieve good results.
Ebay or Amazon seem to have the best price.
You need to know your exhaust gas temperatures at wot.

[jimbunyard]

Are you in the Northern Hemisphere? Hot summer raw cooling water can cause engines that are near the edge of acceptable limits (overpropped, dirty hull, dirty prop, poor alignment, clogged filters, etc.) to overheat. Certainly there is no issue, and good reason, to clean the heat exchanger regardless...


For advice on how to, or tips for economical execution, a starting point would be to know the model of the engine...

[DeepFrz]

If you have owned this engine from new and you have never lost any impeller parts then what Lepke says.

However, if you have not owned the engine since new then I would suggest you dismantle the heat exchanger and mixing elbow to check for impeller bits and to clean the raw water side of the cooling system. The next best thing would be to back flush the system with Rydlime.