Heat exchnager and shaft cooling hose servicing

[Risk Adverse 4]

I have a 20 hp Beta Marine diesel which is three years old. The enhgine manual shows tht the heat exchnage should be serviced annually.  Is flushing the raw-water circuit with fresh water sufficient, or should I remove the heat exchanger and clean it with a marine-grade descaling solution?

If descaling is recommended, which products are safe to use? Should the shaft-cooling hose also be removed and cleaned separately, and are there any risks associated with circulating a descaling solution through the shaft seal or stern tube?

If the heat exchanger needs to be removed, I have heard that using a wooden dowel to clear the cooling passages is safer than using metal tools, which could damage the tubes. Is this correct? Are there any recommended cleaning techniques when cleaning the build up inside the heat exchanger tubes?

[Psyche 976]

Best to ask the local Beta agent what they recommend, that said typically a HE service involves removing the inlet cover and making sure there is no crud build up, you can poke a wire rod down the tubes but at 3 years they should be reasonably clear. You would be surprised what gets past the raw water pump though, it's all pretty basic and well within the ability of someone who can change their own oil. Stern tube- highly unlikely to block. Descaler is typically a weak phosphoric acid solution, highly unlikely to be needed at 3 years, Ive never needed it.  Check the raw water inlet strainer while you're at it, usually problems start there.

 

 

[K4309 470]

2 hours ago, Risk Adverse said:

I have a 20 hp Beta Marine diesel which is three years old. The enhgine manual shows tht the heat exchnage should be serviced annually.  Is flushing the raw-water circuit with fresh water sufficient, or should I remove the heat exchanger and clean it with a marine-grade descaling solution?

If descaling is recommended, which products are safe to use? Should the shaft-cooling hose also be removed and cleaned separately, and are there any risks associated with circulating a descaling solution through the shaft seal or stern tube?

If the heat exchanger needs to be removed, I have heard that using a wooden dowel to clear the cooling passages is safer than using metal tools, which could damage the tubes. Is this correct? Are there any recommended cleaning techniques when cleaning the build up inside the heat exchanger tubes?

I've got a Beta 35.

No, flushing the hot water circuit with fresh water is absolutely no good, unless you do it EVERY time you use the engine and remove all the salt before shutting the engine down. The heat induces scale (calcification) which reduces the efficiency of heat transfer and blocks your tubes. Eventually your engine will overheat, generally just when you need it to really push your boat in some sub-optimal conditions.

Mechanically cleaning the HE tubes is a pain. The commercial products are Barnacle Buster or Rydlyme. Chemical de-scalers.

Last time I spoke to Andy at the Engine Room (Beta Engine supplier), they use Rydlyme. Probably due to price, when you see what the barnacle buster costs, although the Rydlyme isn't cheap either when you account for the dilution factors of both products.

If you look at the MSDS for Barnacle Buster, is is something like 80% Phosphoric Acid with a little bit of surfactant. I buy 5l of 85% phosphoric acid and just use that (diluted 5:1). Phosphoric acid is used in many food / beverage processes such as home brewing, so is available from a number of non-marine places, at about a 5th of the cost. It is also a food ingredient in things like Coca Cola.

Previously I've gotten it from The Sourcery and Chemmate, Chem Mate - Home Of All Your Chemical Cleaning Needs

My last order from Chemmate was 5l for $78 delivered, although the delivery was VERY slow, as it's a hazardous good or something.

Generally, getting the tube stack out is a pain, you have to take the alternator off, and spill salt water and coolant all over your engine (haven't worked out how to get the tube stack out without doing that yet). You should also replace the O rings on the cover plates if you do that.

Additionally, I have a hydraulic gearbox with a gearbox oil cooler. That actually blocks up faster than the engine tube stack. Getting that all dissambled is a classic boat job (hard to access, easy to spill stuff everywhere, always skin knuckles etc...)

SO - I've made up an in-situ recycling system. I have a threaded hose tail that screws in where the engine anode goes at the rear of the HE, and fit another hose tail into the rubber boot upstream of the heat exchangers (downstream of the raw water pump). Two long hoses into buckets sitting on the floor. Dilute the phosphoric acid to 20% ish, use a jug and funnel to pour the mixture in one end, and it naturally drains out the other. On the discharge side, make sure a point in the hose is higher than the top of the HE, so you submerge the whole HE, rather than just running the phosphoric acid around the lowest point.

When you first to it, the water will come out looking grubby and grey. Continue flushing it through with fresh mixture until it's coming out looking clean. Flush well with clean water immediately on finishing. Basically, google the instructions for Barnacle Buster and copy them, it's the same stuff but at a fraction of the price.

You shouldn't need to flush the stern tube. The HE causes calcification due to heat, and there shouldn't be any heat in the stern tube. The need to clean the HE is a completely different issue to raw sea water flushing the stern tube.

Pro tip for blocked heads, the phosphoric acid will also de-scale the waste pipes that foul up with what ever urine and salt water does when they sit too long. One caveat, be cautious of metal fittings in your waste system, such as through hulls. I aren't across what the phosphoric acid does to old bronze through hulls.

[Panache 7]

Acetic acid works well, its is marketed as non toxic and enviornmentally friendly. You can buy it in powder form as concrete etcher from hardware stores. It disssolves the calcium build up and is cheap. You would have to check and make sure it doesn't damage the seals or housings of your heat exchanger. Mine is aluminium, copper and nitrile seals, so far it has worked great.

[aardvarkash10 1,187]

On 18/09/2026 at 9:51 AM, Panache said:

Acetic acid works well, its is marketed as non toxic and enviornmentally friendly. You can buy it in powder form as concrete etcher from hardware stores. It disssolves the calcium build up and is cheap. You would have to check and make sure it doesn't damage the seals or housings of your heat exchanger. Mine is aluminium, copper and nitrile seals, so far it has worked great.

Vinegar.  Typically between 6 and 8% acetic acid.

And you can make a tasty vinegrette afterward.

[LBD 240]

Oxalic acid has been by go to for 50 some years servicing marine heat exchangers.

[Island Time 1,359]

+ 1 for phosphoric Acid. That's what barnacle buster is. Easy to buy, and a food grade acid. You can leave it in the engine overnight without issues, it has no effect on Aluminium, rubber, paper gaskets, or sealant. I've been using it for years on my own boats and customers ones without a single problem.