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Old 03-25-2015, 01:59 PM   #1
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Heat Exchanger Fouling Solution?

I have a Perkin's 4.236 in a small trawler I keep in the salt water in one of the river outlets off Boston Harbor. I moved my mooring recently up river a bit and for whatever reason the fouling within my cooling system, particularly heat exchanger and oil coolers has gotten out of control. I have a strainer on the intake, and change the zincs annually, but inevitably half way through the season my temp starts rising and when I remove the end cap on my heat exchanger it's full of growth and half the tubes are plugged up, usually along the bottom half of the exchanger where the water pools. My particular heat exchanger only has a removable cap on the intake end of the exchanger. I can rod out the tubes of the exchanger, but from what I understand it's best to do this against the flow, which I am unable to do.

To make matters worse, due to my engine installation, it's nearly impossible to pull the heat exchanger or open up the hoses to it without stripping all the components off of my engine. It's full days work just to get the exchanger on/off the engine.

So my question is, does anyone have any tips or tricks that might solve my issue? can I add something in the strainer periodically through the season that might kill the growth? Has anyone ever tried mounting the heat exchanger off the engine in a more accessible place?
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Old 03-25-2015, 02:38 PM   #2
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Greetings,
Welcome aboard. What kind of growth? Barnacles? Slime? Algae?
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Old 03-25-2015, 02:43 PM   #3
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Mostly crusty formations.. like the early stages of mussels and barnacles.
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Old 03-25-2015, 02:51 PM   #4
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Commonly done -

Rig up a fresh water flush system. With your seacock closed and water turned on, operate your engine at about 700 RPM and run fresh water through it for a few minutes. Do not run water with engine off. Do not open seacock until your next outing, critters do not like fresh water.

Caps are sold that will fit on most sea strainers to accommodate this setup.
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Old 03-25-2015, 03:01 PM   #5
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Greetings,
Mr. pd. The next time you get a sample of the "growth", place it in some vinegar to see if it dissolves (barnacle shells are calcite). Maybe you can periodically fill your cooling system with vinegar and prevent/dissolve blockages. Just a guess but it might minimize/eliminate disassembly of the whole system.
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Old 03-25-2015, 03:05 PM   #6
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Quote:
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Commonly done -

Rig up a fresh water flush system. With your seacock closed and water turned on, operate your engine at about 700 RPM and run fresh water through it for a few minutes. Do not run water with engine off. Do not open seacock until your next outing, critters do not like fresh water.

Caps are sold that will fit on most sea strainers to accommodate this setup.
just want to stress the DO NOT RUN WATER WITH ENGINE OFF part. That is all.
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Old 03-25-2015, 03:48 PM   #7
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If you are on a mooring you don't have dock water available to do a fresh water flush. But you can use your boat's potable water system.

On my boat I have a hose bib in the aft cockpit that is very convenient to hook up a garden hose to. Then I just hook it to a flush attachment on the top of the strainer. I start the engine with the thru hull open but then close it and let it run on fresh water only supplied by the boat's tank. After a few minutes I close the fresh water valve and quickly shut down the engine. Then I open the sea cock to be ready to go next time.

You can run for a few seconds with no water flow. But it is important not to pressurize the raw water system without the engine running. It can blow the seals on the raw water pump. That is why I leave the seacock open when I connect the fresh water so it will not pressurize the system. After starting the engine I close the seacock.

As others have said, marine critters don't like fresh water.

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Old 03-25-2015, 04:20 PM   #8
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just want to stress the DO NOT RUN WATER WITH ENGINE OFF part. That is all.


Why?
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Old 03-25-2015, 04:32 PM   #9
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Water pressure can backfill into the motor if the motor is not running . I flush my motor using a 10 gallon bucket and an extra strainer cap with a hose barb mounted in it. The motor sucks the freshwater from the bucket. I close the through hull to ensure only freshwater is being used. Make sure you put the old strainer cap back on and then reopen (or leave closed) the through hull. I occasionally throw in a little salt away when I know the boat might sit longer than usual.
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Old 03-25-2015, 05:01 PM   #10
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Blue Yonder is correct, you can end up with water inside the engine. The same thing can happen if you continue to crank a boats engine that will not start btw.
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Old 03-25-2015, 05:21 PM   #11
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There are flushing/descaling products like Rydlyme, Barnacle Buster, Triton Green, etc. that could help, depending on the fouling you're experiencing.

Two ways to do it on engine: "import" enough to fill the raw water system using the engine's raw water pump and let it sit for a bit... or cobble together a loop so you can pump the stuff through and recirculate it for a couple hours.

Both would likely depend on whether it's easy for you to each easy inlet and discharge places (for example, in through a sea strainer, out from the hose that leads to the exhaust elbow). In the first method, the raw water pump impeller stays in and does some work. In the second method, the impeller comes out and an off-engine pump of some sort does the work. In both instances, any zincs come out first, too... 'cause the stuff will probably eat any existing zincs anyway.

It doesn't take the place of our scheduled aftercooler (etc.) service regime, but the advantage for us is that I can do the sea strainer, fuel cooler, aftercooler, gear cooler, and heat exchanger all at once.

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Old 03-25-2015, 05:40 PM   #12
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I'm doing that regular service on my boat next week. Aftercooler, heat exchanger, Oil, fuel and transmission coolers. Holy Guacamole! I'm glad I only have one motor to pay for.

I've seen some setups that use a fitting that goes where the first zinc in your raw water system goes. Output from the cooling water injection hose back into the bucket with the chemical. Get a cheap 12v bilge pump and connect the water output to the zinc fitting. Turn on the pump and run until the foaming stops. This can be used to clean air conditioner systems also. Be careful, use eye protection and don't let anyone convince you to use muriatic acid.
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Old 03-25-2015, 06:25 PM   #13
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I bought a household sump pump @ Lowe's, rigged a loop from the raw water intake hose to outlet hose on exhaust elbow, Then used Rydlyme to flush system. Ran about 3hrs until stuff stopped foaming. Repeated with fresh water. It was later suggested that I should have flushed system in reverse to clear any trapped gook. We have Detroit 82L's in our Californian. Certainly cleared out a lot of stuff. Loop is not hard to set up; some PVC pipe & a bucket.
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Old 03-25-2015, 07:08 PM   #14
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thanks for all of these ideas! I wonder if it's possible to invent a pencil zinc with some sort of slow release biocide? In the meantime, I'm going to put some of these ideas to the test.
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Old 03-25-2015, 07:53 PM   #15
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I have the same engine. I never noticed marine growth but have had your normal calcification in the tubes. I rigged a semi closed acid wash with a cheap bilge pump and some hose. You should have seen the crud that settled in that bucket. I know this will not help the quick growth but giving it a deep clean might buy you some time.
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Old 03-26-2015, 06:38 AM   #16
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Confused. If I attach a fresh water hose to the raw water intake strainer / thru hull, how does it back flow into the engine. The only connection with the fresh water system is the heat exchanger.
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Old 03-26-2015, 07:21 AM   #17
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Confused. If I attach a fresh water hose to the raw water intake strainer / thru hull, how does it back flow into the engine. The only connection with the fresh water system is the heat exchanger.

The system I described would flow from supply bucket to 115V (in my case) transfer pump to flush adapter (in our case, this sits between seacock and sea strainer) and then through water pump (impeller removed), fuel cooler, aftercooler, gear cooler, heat exchanger (raw water portions, only)... and then gets captured from the hose leading to the exhaust elbow... and is routed back to the supply bucket for continuous recirculation.

The descaler never enters the "freshwater" (anti-freeze) side of the cooling system, never enters cooling passages in the block, etc. That side gets a different process, for us: drain/capture/recycle old antifreeze, flush with a different product (Fleetguard's "Restore" in our case), then fill with new anti-freeze.

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Old 03-26-2015, 07:57 AM   #18
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About the same in my photo above, but the 4.236 does not have a fuel cooler. I connected the hose from the 12v pump directly to the oil cooler then disconnected the hose going into the elbow and routed it back into the bucket. I completely left the raw water pump out of the equation.

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The system I described would flow from supply bucket to 115V (in my case) transfer pump to flush adapter (in our case, this sits between seacock and sea strainer) and then through water pump (impeller removed), fuel cooler, aftercooler, gear cooler, heat exchanger (raw water portions, only)... and then gets captured from the hose leading to the exhaust elbow... and is routed back to the supply bucket for continuous recirculation.

The descaler never enters the "freshwater" (anti-freeze) side of the cooling system, never enters cooling passages in the block, etc. That side gets a different process, for us: drain/capture/recycle old antifreeze, flush with a different product (Fleetguard's "Restore" in our case), then fill with new anti-freeze.

-Chris
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Old 03-26-2015, 05:20 PM   #19
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Confused. If I attach a fresh water hose to the raw water intake strainer / thru hull, how does it back flow into the engine. The only connection with the fresh water system is the heat exchanger.
Lengthy periods of turning the starter can cause water to build up in the exhaust line to the point it back-flows through the exhaust manifold, runs past the exhaust valves and fills the cylinders. The same can happen if you run water through it.
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Old 03-26-2015, 09:41 PM   #20
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You can also take a 5 gallon bucket with a bilge pump in it, fill 3/4 full with hot water and cooling system cleaner (radiator flush). Run a hose from the bilge pump to one end of the cooler, run a hose from the other end back into the bucket. You'll be surprised at the crud you'll flush out, depending on how many hours a year do this every year or 2. Good luck
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