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Yanmar Heat Exchanger Corrosion


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Posting this to maybe help others avoid this problem on the Yanmars and other engines with aluminium body heat exchanger/exhaust manifolds. This is my Yanmar 4JH4E

A few months ago I noticed salt crystals forming around the forward HEX end cap

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and20210725_140415.thumb.jpg.d2423f32bd771d67cd0c1e2fc8338950.jpg

and when pulled apart this was the situation

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and yet the rear one is just about in perfect condition

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What is noticeable is that the corrosion is on the part of the face between the clamping bolts. Will need to check if the face of the cover plate is dead flat. Hoping that Rocke can work his welding magic on this, otherwise it will be new one from USA  -already priced it up.

James Mobberley at Moon Engines recommends setting up a fresh water flush for these engines, a tee and a valve on the salt water intake. Had a look at a friend's 75hp Yanmar, and we could see signs of salt crystals, then he mentioned that his alternator had been damaged by salt water.

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Being a sealed system, heat exchanger separate to normal cooling, why would you not have fresh water in there with a rust/corrosion inhibiter?

Just like car with alloy heads

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1 hour ago, Fogg said:

How old and how many hours?

The engine is 16 yrs old, but has only been in service 6 yrs, 1000hrs. The more i look at this the more I am convinced this was a manufacturing/assembly defect. When the weld repair is machined they will ensure all parts mate perfectly.

If you have a Yanmar, have a good look around those end caps - noting the turbo versions have a quite different heat exchanger

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1 hour ago, harrytom said:

Being a sealed system, heat exchanger separate to normal cooling, why would you not have fresh water in there with a rust/corrosion inhibiter?

Just like car with alloy heads

Because it's a heat exchanger, one side is fresh, one side is salt (raw) to allow the heat exchange.

This issue is common on these engines and the D series Volvo Pentas.

The manufacturers say this is why they are insistent on the right coolant in the fresh water side, and that it is changed at the correct interval.  It's also important to ensure that the models with electrically isolated sail drives are, in fact, still electrically isolated! There is a plastic gasket, and plastic inserts/washers on the saildrive mounting bolts for this reason.

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5 hours ago, Island Time said:

Because it's a heat exchanger, one side is fresh, one side is salt (raw) to allow the heat exchange.

This issue is common on these engines and the D series Volvo Pentas.

The manufacturers say this is why they are insistent on the right coolant in the fresh water side, and that it is changed at the correct interval.  It's also important to ensure that the models with electrically isolated sail drives are, in fact, still electrically isolated! There is a plastic gasket, and plastic inserts/washers on the saildrive mounting bolts for this reason.

Beta and Nanni and just about everyone else use the same concept

Beta:

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Nanni

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notable that they both use 3 bolt end caps compared to the Yanmar's 2 bolt. Maybe they figured out these are a problem.

The guys at Moons said they believe all the European assembled marine engines source their Heat Exchanger/Exhaust manifolds from an Italian OEM supplier, Mota.

Fogg's turbo Yanmar is different, those are assembled in Japan c.f mine which came out of Yanmar's Netherlands factory.

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On Vivaldi there is a hose fitting on the suction side just after the sea cock for the salt water inlet. We can shut off the salt water side and run fresh through it which is pretty handy for the occasional rinse out. 

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14 hours ago, Vivaldi said:

On Vivaldi there is a hose fitting on the suction side just after the sea cock for the salt water inlet. We can shut off the salt water side and run fresh through it which is pretty handy for the occasional rinse out. 

That's exactly what James Mobberly recommends, he also suggests using one of the salt removal products, eg Saltaway. Said he was not so keen on Barnacle Buster, has found it is too aggressive and has caused problems with seals, gaskets etc.

He did highlight you need to be using some sort of container to hold the fresh water and let the salt water pump suck it into the engine via a hose to the Tee you mention. Some people have plumbed up direct fresh water hose connections to the downstream side of the salt water pump and this has resulted in flooded engines 

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2 hours ago, marinheiro said:

That's exactly what James Mobberly recommends, he also suggests using one of the salt removal products, eg Saltaway. Said he was not so keen on Barnacle Buster, has found it is too aggressive and has caused problems with seals, gaskets etc.

He did highlight you need to be using some sort of container to hold the fresh water and let the salt water pump suck it into the engine via a hose to the Tee you mention. Some people have plumbed up direct fresh water hose connections to the downstream side of the salt water pump and this has resulted in flooded engines 

Yeah you don’t want to pressurise it. The hose I use has a T fitting just after the tap that allows pressure water to run to waste. The water pump sucks what it needs and the flow can be adjusted with the tap

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On 5/08/2021 at 7:50 PM, marinheiro said:

Fogg's turbo Yanmar is different, those are assembled in Japan c.f mine which came out of Yanmar's Netherlands factory.

Thanks. Do you know if that makes mine any better or still equally susceptible?

As usual, other people know more tech info about my boat than I do…

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2 hours ago, Fogg said:

Thanks. Do you know if that makes mine any better or still equally susceptible?

As usual, other people know more tech info about my boat than I do…

you need to look around where the 2 arrows are, especially on the underside, sorry cannot find a rear view of the engine.

at the front look between the alternator and the hoses above it.

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even if you do not see any salt leakage, I would suggest if the engine is more than 5 yrs old as preventive maintenance, you should be taking the end caps off, checking the seals and sealing surfaces and getting the heat exchanger tube bundle cleaned, the last especially seeing as your yacht has come from a warm water environment.

If you have any doubts I am sure IT would check it out for you 😄

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