Apologies for the repeat post, I have searched the forum and can't find the discussion that I know is there somewhere.

I'm just wanting to know what the acid is that is recommended for flushing the cooling system on a marine diesel. There are a few products around that are marketed specifically for this such as Barnacle Buster
www.proactivemarine.com.au/sites/default/files/Barnacle%20Buster%20-%20Seawater%20Engine%20Cooling_pro.pdf
but I have seen people discuss using other options based on the active agents in the purpose made products.

any pointers on where these can be sourced?

Brick cleaner / hydrochloric acid + detergent from the big green shed. I remove the tubes from the heat exchange and put them in a tub of the concoction, it fizzes up and come out like new. Might not be so good as a flush as it might attack rubber bits

I use Metal Gleam which is a locally made product which I'm sure is the same as Barnacle buster at probably the fifth of the cost.

Here is a previous thread.

www.seabreeze.com.au/forums/Sailing/General/Bukh-DV20-water-jacket-flush?page=1

Thanks for the info guys.

Helpful as always

So I have been looking into this a bit more and I have a couple of questions I'm hoping the more engineer / mechanically talented people can assist with.

Below is a diagram of my engine (Volvo Penta MD7b). Reading the directions for the "open loop recirculation process" published by the promoters of the Barnacle Buster solution they suggest to "choose an injection point as close to the sea water valve as possible". So somewhere between part 54 and 26 along the water intake pathway on the diagram. That's easy enough done and the flush solution would travel from the water pump (part 21) (having removed the impeller so the solution could flow through) outlet to the thermostat (7) housing inlet.
For the recovery / outlet point they suggest to "look for a hose or fitting just after the heat exchanger. Most often, this hose will lead to the exhaust / water mixing elbow". It's just cut off the number in my diagram but I'm thinking this would be where the pipe (67) joins the exhaust elbow.

My questions are as follows:
1) The directions make no mention of running the engine up to temp prior to running the flush solution through so would this not mean that the thermostat would be closed and no solution would flow through the exhaust manifold?

2) The Barnacle Buster "immersion cleaning instructions" do call for the engine to be run up to operating temp before introducing the flush solution while the engine is running. Once the flush solution is introduced they say to run it through until it is coming out the exhaust, cut engine and let it sit in the system for a period of time before rinsing out with fresh water. So this would see the solution pass through the exhaust manifold. Is it safe to do this given that there is a connection between the exhaust manifold and the engine through the openings on the side of the manifold where it connects to the engine.?

3) Is this engine from a time prior to heat exchangers and the direct raw water cooling means it is just not appropriate to be considering this process with this particular engine? If I want to clean out the exhaust manifold does that mean taking it off and immersing it in a bucket of solution rather than running it through the engine?


I realise that these are probably some pretty basic questions but having never tackled anything like this before messing around with the engine makes me a bit nervous. But I'm keen to give it a go if I feel I understand what I'm doing.

Thanks in advance for your assistance.

I've done this with vinegar, which dissolves calcium from shells, etc. As per your step 2; run the engine up to working temperature, i.e. coming back to to dock, let the engine idle a few minutes but still warm, and then I would stop the engine, undo a rubber inlet hose and pop that into a bucket/bottle of vinegar, from 2 to 5 litres. Once the colour is seen out the exhaust, then shut down the engine, and let the solution sit for a few hours or days. It's a very weak acid.
As with most chemistry, extra warmth makes reactions faster. I had a rubber hose just aft of the raw water strainer which I tapped into/ popped into the bucket. A hose that sucks intake water into the engine. Mine was a Yanmar YSE8, a raw water cooled 'agricultural' class motor.
No need to remove any impeller. Just connect a 12 mm (or whatever) hose pipe from your vinegar/BarnacleBuster bucket into your water pump or RW strainer. After closing the sea water tap of course. The pump should be able to suck it.

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FabulousPhill said..
I've done this with vinegar, which dissolves calcium from shells, etc. As per your step 2; run the engine up to working temperature, i.e. coming back to to dock, let the engine idle a few minutes but still warm, and then I would stop the engine, undo a rubber inlet hose and pop that into a bucket/bottle of vinegar, from 2 to 5 litres. Once the colour is seen out the exhaust, then shut down the engine, and let the solution sit for a few hours or days. It's a very weak acid.
As with most chemistry, extra warmth makes reactions faster. I had a rubber hose just aft of the raw water strainer which I tapped into/ popped into the bucket. A hose that sucks intake water into the engine. Mine was a Yanmar YSE8, a raw water cooled 'agricultural' class motor.
No need to remove any impeller. Just connect a 12 mm (or whatever) hose pipe from your vinegar/BarnacleBuster bucket into your water pump or RW strainer. After closing the sea water tap of course. The pump should be able to suck it.

I did a comparison test with some seashells years ago. One jar had vinegar, One CLR and the other one Metal Gleam,[phosphoric acid mainly with a couple of others]. Same amount of seashells in each jar. The vinegar was extremely slow, the CLR was a little bit better. The metal Gleam frothed up instantly and the shells were completely gone in 20 minutes.

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MattM14 said..

So I have been looking into this a bit more and I have a couple of questions I'm hoping the more engineer / mechanically talented people can assist with.

Below is a diagram of my engine (Volvo Penta MD7b). Reading the directions for the "open loop recirculation process" published by the promoters of the Barnacle Buster solution they suggest to "choose an injection point as close to the sea water valve as possible". So somewhere between part 54 and 26 along the water intake pathway on the diagram. That's easy enough done and the flush solution would travel from the water pump (part 21) (having removed the impeller so the solution could flow through) outlet to the thermostat (7) housing inlet.
For the recovery / outlet point they suggest to "look for a hose or fitting just after the heat exchanger. Most often, this hose will lead to the exhaust / water mixing elbow". It's just cut off the number in my diagram but I'm thinking this would be where the pipe (67) joins the exhaust elbow.

My questions are as follows:
1) The directions make no mention of running the engine up to temp prior to running the flush solution through so would this not mean that the thermostat would be closed and no solution would flow through the exhaust manifold?

2) The Barnacle Buster "immersion cleaning instructions" do call for the engine to be run up to operating temp before introducing the flush solution while the engine is running. Once the flush solution is introduced they say to run it through until it is coming out the exhaust, cut engine and let it sit in the system for a period of time before rinsing out with fresh water. So this would see the solution pass through the exhaust manifold. Is it safe to do this given that there is a connection between the exhaust manifold and the engine through the openings on the side of the manifold where it connects to the engine.?

3) Is this engine from a time prior to heat exchangers and the direct raw water cooling means it is just not appropriate to be considering this process with this particular engine? If I want to clean out the exhaust manifold does that mean taking it off and immersing it in a bucket of solution rather than running it through the engine?


I realise that these are probably some pretty basic questions but having never tackled anything like this before messing around with the engine makes me a bit nervous. But I'm keen to give it a go if I feel I understand what I'm doing.

Thanks in advance for your assistance.

With the MD7b it is straightforward. No need to run the motor. The engine is raw water cooled and the calcium build up occurs mainly where the saltwater first encounters heat At the thermostat. You will need a couple of pieces of 20mm rubber hose and some plastic push on joiners. Pull off the hose at the water pump, the side that goes to the engine and add some hose to it and lash it so that the end is higher than the cylinder head. Don't worry about the pump it will be clean. Pull off the hose at the other side where the water leaves the block, the end that goes up to the anti syphon[65]. Blow the water in the block out. It's easy and there is not much there! Lash the hose up the same height as the first hose and pour in your acid mix, use a funnel. Only takes a 1/3 of a bucket or so.
Put the kettle on and relax for half an hour or so. It will froth up a bit as the calcium dissolves. When you are satisfied it's finished, drop one end of the hoses into a bucket and check what comes out. Button up the hoses and run the engine.
I have a 20 litre plastic container with a $20 pump that I can put into the circuit and continuously pump acid about but the static method works well.

If you are referring to the exhaust elbow where the salt water enters the exhaust I would suggest leaving that alone unless you are having performance problems.

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Ramona said..

With the MD7b it is straightforward. No need to run the motor. The engine is raw water cooled and the calcium build up occurs mainly where the saltwater first encounters heat At the thermostat. You will need a couple of pieces of 20mm rubber hose and some plastic push on joiners. Pull off the hose at the water pump, the side that goes to the engine and add some hose to it and lash it so that the end is higher than the cylinder head. Don't worry about the pump it will be clean. Pull off the hose at the other side where the water leaves the block, the end that goes up to the anti syphon[65]. Blow the water in the block out. It's easy and there is not much there! Lash the hose up the same height as the first hose and pour in your acid mix, use a funnel. Only takes a 1/3 of a bucket or so.
Put the kettle on and relax for half an hour or so. It will froth up a bit as the calcium dissolves. When you are satisfied it's finished, drop one end of the hoses into a bucket and check what comes out. Button up the hoses and run the engine.
I have a 20 litre plastic container with a $20 pump that I can put into the circuit and continuously pump acid about but the static method works well.

If you are referring to the exhaust elbow where the salt water enters the exhaust I would suggest leaving that alone unless you are having performance problems.

Thanks Ramona, I think even I could manage that

I had been thinking that another option would be to take the raw water inlet hose from a point before the pump and stick that into a bucket of flush solution and just run the engine until say half the fluid has run through. Let it sit for a few hours, run the engine again for the remainder of the fluid then flush with fresh water. Would there be any problems with this method?

I have also been thinking of the cheap pump circulation set up. Am I correct in thinking that this would involve taking the hose off the engine side of the pump as you suggest and connecting this to an in line pump with the uptake in a bucket of flush solution. Take the hose from the anti syphon and put this into the bucket so it completes the circuit and discharges back into the bucket ready to be sucked up again?

Thanks again for your input on this Ramona and to all others who have contributed.

Just pull the hose off after the pump and fill the block with the acid of choice. There is a surprisingly small amount of coolant in the block water passages, the head is not cooled. When you button it back up and start the engine the seawater will flush out the acid and crud. Metal gleam does no harm to the cast iron and brass bits in the thermostat so you could leave the solution there for a couple of days if you wanted.
The pump set-up is hooked up the same way. Just with the pump you can watch the crap heading into the container. This is better suited to cleaning the saltwater side of heat exchanger engines.

With the MD7b I found the block needs a flush about every 18 months or so.

Best done with a warm engine, otherwise the thermostat, being closed, will prevent or at least slow down the flow through the engine.

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wongaga said..
Best done with a warm engine, otherwise the thermostat, being closed, will prevent or at least slow down the flow through the engine.

There is always a small bypass hole. The acid can be added to either hose end too. Warm water mixed with the acid [5:1] will make the acid work faster though.

With the MD7b the thermostat is easy to get to and it might be a good time to check it's there and is working correctly.

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Ramona
With the MD7b it is straightforward. No need to run the motor. The engine is raw water cooled and the calcium build up occurs mainly where the saltwater first encounters heat At the thermostat. You will need a couple of pieces of 20mm rubber hose and some plastic push on joiners. Pull off the hose at the water pump, the side that goes to the engine and add some hose to it and lash it so that the end is higher than the cylinder head. Don't worry about the pump it will be clean. Pull off the hose at the other side where the water leaves the block, the end that goes up to the anti syphon[65]. Blow the water in the block out. It's easy and there is not much there! Lash the hose up the same height as the first hose and pour in your acid mix, use a funnel. Only takes a 1/3 of a bucket or so.
Put the kettle on and relax for half an hour or so. It will froth up a bit as the calcium dissolves. When you are satisfied it's finished, drop one end of the hoses into a bucket and check what comes out. Button up the hoses and run the engine.
I have a 20 litre plastic container with a $20 pump that I can put into the circuit and continuously pump acid about but the static method works well.

If you are referring to the exhaust elbow where the salt water enters the exhaust I would suggest leaving that alone unless you are having performance problems.

I am the owner of a 2GM20 subject to satisfactory survey. Sea trials yesterday went well but planning on giving the Yanmar some love.

It appears the 2GM20 is a similar technique to above, I assume I pull anodes and thermostat out first? After flush intend to change all flex hoses, oils, filters, anodes, valve adjustment, impeller and maybe a new fuel lift pump as the current one has a leak. Anything else particular to look for, the stainless exhaust bend looks to be a couple of years old.

If this is just a precautionary acid flush there is no need to remove the thermostat. If there have been heating issues it might be an idea to pull the thermostat and check the opening temperatures.