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Old 06-02-2012, 02:44 PM   #1
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Do you Flush? How Often? With What?

Hey there - Its actually a serious question. I have a 3208 natural Cat (210hp) and have never flushed the exchanger. Is there a consensus in the group as to if/how often this should be done. I've read somewhere that muriatic acid works well, but I've never used it - advice/safety tips. Thanks!
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Old 06-02-2012, 03:46 PM   #2
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Consensus? I doubt it. I remove my main heat exchanger, and oil and tranny coolers every 2 or 3 seasons and flush them out with freshwater. This winter I used some muriatic acid becuase the crud was sticking in the tube walls. I went full strength, but only let it dribble thru, then I flushed with fresh water. And I change raw water impeller every 2 seasons.
That's what works for me.
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Old 06-02-2012, 05:16 PM   #3
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Thanks Guru - I think its time as I don't seem to be getting the same volume of water through as I used to, even with a new raw water impeller. Thanks Again
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Old 06-02-2012, 05:29 PM   #4
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I would inspect the face of the heat exchanger first. We change the raw water impeller every year (I was told every 4-600 hours). Since I have drained the water to the pump, I also inspect the heat exchanger, oil and transmission coolers. I have had to clean some crap off the face of the heat exchanger but I have never flushed it.
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Old 06-02-2012, 06:24 PM   #5
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Thanks Guru - I think its time as I don't seem to be getting the same volume of water through as I used to, even with a new raw water impeller. Thanks Again
Be sure and check any screens in the raw water system too. Like your oil cooler inlet (this is usually where impeller blades get caught) and the water lines around to the exhaust manifold. Any low spots will hold water when the engines are not running and salt and minerals will leech out of solution and form deposits over time.

Also, with the engines idling, use your fingers and squeeze your raw water hoses between the pump and cooler . If the hoses are swollen up or feel hard, that's back pressure and you probably have a blockage somewhere in the system.

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Old 06-03-2012, 11:54 AM   #6
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Probably depends on the type of engine and raw water system layout and your boating environment. We have FL120s and we have never had the main heat exchangers flushed or inspected. We change the raw water pump impellers every five years or so and with the modern Johnson pumps the impeller that comes out looks exactly like the impeller that's going in. We change the engine coolant every six years or so, although the trend now is to have coolant tested and analyzed every so often and change based on that rather than on any sort of timetable.

But your engines in your climate may be a whole different deal. If it was me I would consult a reputable local diesel shop familiar wth your type of engine and raw water setup and follow their advice, which is what we did.
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Old 06-03-2012, 06:00 PM   #7
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I just went thru this myself on my FL120. Since the exchanger is so easy to remove and clean I will likely do as a matter of maintenance in the future. I too had hard deposits and a lot of rust from the metal tube that it connects to on the starboard side. I capped the end and filled the exchanger with CLR and let it stand a few minutes. Rinsed it thoroughly and put it back on. I got my flow back and my engine temps are normal. Did the same on my trans oil cooler when I was rebuilding the trans.
That metal tube I mentioned is getting replaced with a piece of Vernatube too.

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Old 06-03-2012, 06:22 PM   #8
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The Lehman heat exchange should be serviced at least annually. The procedure is to shut off the raw water inlet, and remove the end caps. They are held on with a single bolt in the center. This will spill the raw water inside. Inspect the tube ends and clean gently as needed (metal tools can damage the tubes). Remove any old zinc parts, and replace the zinc. Reinstall the end caps using new rubber gaskets.

This procedure will ensure that the raw water side of the heat exchanger is not blocked and that there is a new zinc with the old zinc parts removed.

I have found that in the PNW there is a crusty growth on the tube ends and about 25% of the tubes were either blocked or partially blocked after a year.
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Old 06-03-2012, 06:58 PM   #9
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i had a sportfish with 3208 ta's...it wasn't the main heat exchanger on them that was a problen...it was that aft oil cooler that stays wet and more likely to clog with marine life...by the time I learned that lesson...I had to resort to a cat dealer to even take the thing apart...expensive!!!
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Old 06-03-2012, 10:05 PM   #10
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We asked our diesel shop, which works on hundreds of boats with FL120s, how often we should check and clean the main heat exchangers. They said when we notice a rise in average engine temperature and/or a decrease in exhaust water flow. So far neither one has happened. We have cupro-nickel exchangers if that makes any difference. We change the exchanger zincs every six months although there is always plenty left of the old ones we take out.
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Old 06-04-2012, 08:05 AM   #11
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Larry - how do you clean the tubes? Thanks - Kevin O
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Old 06-04-2012, 01:17 PM   #12
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To rod out the tubes, I have used a wood dowel. Use an undersize dowel, if the dowel jams in the tube, it's too big. Not all the tubes can be reached due to the end cap support. A brass gun cleaning brush of .17 caliber can be used. If the fouling is just at the tube ends, a phillips screwdriver can be twisted VERY GENTLY against the tube ends to remove the crusty stuff. Flushing with a freshwater hose with a nozzle also works. Inspecting with a light held at the other end shows the condition of the tubes.

Be careful not to damage the tubes, which are copper, copper nickle or brass.

If you see that the fouling is extensive, removing the heat exchanger and soaking in vinegar, CLR, or taking the exchanger to a radiator shop is the next step.

The idea here is to inspect and clean, to determine the fitness of the exchanger. Marin's way is to wait till the blockage is enough to cause the engine temp to rise.

I prefer to do an annual inspection and clean as needed so I know I start the season with clean heat exchanger. I have no experience with high fouling areas which may require more frequent inspection.

I was advised to use new rubber gaskets each time, as the old ones may not reseal.
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Old 06-04-2012, 03:25 PM   #13
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To remove the tube bundle. Pull the end cap off the side where the water enters.
In the end cap you will find a devider and two pencil zincs or what is left of them. The other side will have the fuel priming pump mounted to it.

Once off you will see the ends of the tube bundle you should be able to pry gently on the end plate to allow the tube bundle to slide out.

It is long and kind of heavy but not too much. take it to a radiator shop and have it hot tanked and tester for leaks.
If there is a leak the usual fix is to plug the leaking tube both ends

Replace the gasket when reinstalling the tube bundle. It is really as easy as that.

The good thing is you will get to understand exactly how your heat exchanger works. Every engine is different.
This is just something I did on my 3208N.A.

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Old 06-04-2012, 06:09 PM   #14
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skipperdude,

Your post reminds me that my instructions are for the factory heat exchanger on a Ford Lehman 120 engine.

Yours are for 3208NA.

Other engines will have a different procedure.
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Old 06-05-2012, 04:14 AM   #15
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Marin's way is to wait till the blockage is enough to cause the engine temp to rise.
It's not my way, it's the way the pro shops do it, at least the ones I've talked to which includes Northern Lights/Lugger. Some people like to take things apart needlessly to check things when there isn't a problem manifesting itself. Sort of like rebuilding your car's engine every 5000 miles whether it needs it or not.

Others--- like me--- don't have the time to waste chasing unmanifested problems. One of the oil heat exchangers on our boat developed a leak a few years after got the boat. The boat's records showed this heat exchanger had been installed 16 years earlier. I took it off to replace it expecting to find a mess of corrosion and buildup but the inside was imaculate. The raw water tubes had reflections on their interior surfaces from the light coming in the other end.

If we begin to see issues like the ones I mentioned we'll check the main heat exchangers. But so far we haven't, so we haven't.

Besides, we have a spare engine so shoud we get an overheat due to a heat exchanger problem we'll just shut the one engine down and keep going on our way until the problem can be resolved.
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Old 06-05-2012, 07:16 AM   #16
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It's not my way, it's the way the pro shops do it, at least the ones I've talked to which includes Northern Lights/Lugger. Some people like to take things apart needlessly to check things when there isn't a problem manifesting itself. Sort of like rebuilding your car's engine every 5000 miles whether it needs it or not.

Others--- like me--- don't have the time to waste chasing unmanifested problems. One of the oil heat exchangers on our boat developed a leak a few years after got the boat. The boat's records showed this heat exchanger had been installed 16 years earlier. I took it off to replace it expecting to find a mess of corrosion and buildup but the inside was imaculate. The raw water tubes had reflections on their interior surfaces from the light coming in the other end.

If we begin to see issues like the ones I mentioned we'll check the main heat exchangers. But so far we haven't, so we haven't.

Besides, we have a spare engine so shoud we get an overheat due to a heat exchanger problem we'll just shut the one engine down and keep going on our way until the problem can be resolved.
Exactly...it's not a problem that happens overnight. Unless there is an all of a sudden a major blockage at which point your strainer system failed miserably.

Doing the MAIN heat exchangers usually is only done with an unwanted rise in temps or if other major engine maintenance is being done. But I guess if a lot of people on here like to change their oil every 15 minutes...routine cooler cleaning is a great time passer...

But things like oil cooers need a look because their blockage can be masked unless you have an oil temp guage or infrared gun them regularly.

More imprortant than cleaning the coolers is maintaining their zincs and integrity so you don't loose or dilute coolant.
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Old 06-05-2012, 04:41 PM   #17
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My advise came to be from a 40 year expert in Lehman engines, Norm Dibble, who was a mechanic with Pat's Marine Engine, Seattle. When I have serviced my exchanger, there has been fouling and growth as well as the parts of the zinc. Since I only have one engine, a preventable overheat is not acceptable.

I have noticed that boaters with twin engines have the attitude that 'if one engine quits, I have another, so why bother with a lot of preventive maintenance'.

This may work fine if you operate in calm, protected water, with repair and towing available. Try keeping your boat off a lee shore in 10ft swells and 20 knots of wind when your leeward engine overheats!

Consider that the mechanics are not the ones going to be out on your boat if you have a failure. They will be there on land to do the repair when you limp in. Unless you have an accurate overheat alarm, the engine could damage itself by overheating prior to the operator noticing and shutting it down.

All this trouble can be avoided on a Lehman by remove two end caps, with only one bolt per cap, and inspecting the tubes and then replacing two $2 gaskets. If you have never looked, how do you know if you have fouling or not. Just because the exchanger cools the engine with 25% blockage does not mean it will with 40 or 50% blockage?

Marin,

The oil cooler on a Lehman is smaller in diameter and has more relative flow per tube than the heat exchanger. My engine oil cooler was also clean when I changed it, whereas the heat exchanger was fouled.
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Old 06-05-2012, 05:04 PM   #18
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Once every couple of years, I fill the HE with white vinegar, leave it for a week or so and then drain out the resulting slurry. It's a very easy and cheap way to keep it clean. Just fill through the zinc holes - one of mine is on the upper side - and there's a drain plug on the lower side. The Cat 3406 HE is very heavy and difficult to remove - it's at the front of the engine and down low in the bilge - also there are 105 litres of coolant to drain!
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Old 06-05-2012, 05:12 PM   #19
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skipperdude,

Your post reminds me that my instructions are for the factory heat exchanger on a Ford Lehman 120 engine.

Yours are for 3208NA.

Other engines will have a different procedure.

Larry, that is what the belfastcruiser has in his boat A 3208 n.a. He started the tread so I was responding to his query.

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Old 06-05-2012, 09:04 PM   #20
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My advise came to be from a 40 year expert in Lehman engines, Norm Dibble, who was a mechanic with Pat's Marine Engine, Seattle. When I have serviced my exchanger, there has been fouling and growth as well as the parts of the zinc. Since I only have one engine, a preventable overheat is not acceptable.

I have noticed that boaters with twin engines have the attitude that 'if one engine quits, I have another, so why bother with a lot of preventive maintenance'.

This may work fine if you operate in calm, protected water, with repair and towing available. Try keeping your boat off a lee shore in 10ft swells and 20 knots of wind when your leeward engine overheats!

Consider that the mechanics are not the ones going to be out on your boat if you have a failure. They will be there on land to do the repair when you limp in. Unless you have an accurate overheat alarm, the engine could damage itself by overheating prior to the operator noticing and shutting it down.

All this trouble can be avoided on a Lehman by remove two end caps, with only one bolt per cap, and inspecting the tubes and then replacing two $2 gaskets. If you have never looked, how do you know if you have fouling or not. Just because the exchanger cools the engine with 25% blockage does not mean it will with 40 or 50% blockage?

Marin,

The oil cooler on a Lehman is smaller in diameter and has more relative flow per tube than the heat exchanger. My engine oil cooler was also clean when I changed it, whereas the heat exchanger was fouled.
Sure...they need to be inspected and cleaned...but fouling by marine growth/crusting is a VERY gradual thing and your temp guage gives months of warning if you are paying attention.

40 years of experience...great but the facts are that it's gradual enough to check it as your temps slowly rise...it will never be an emergency shutdown unless you ignore it for too long.

As I said before...there's lots of people that would like to change the oil after a daily run because "no mechanic would ever argue with changing the oil too often"...great...after changing the oil, diismantle the coolers for fun...
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