Yanmar Corrosion Question...

[Star-Lord]

Yanmar 3JH3E 1700hrs from 2000.
Engine was lifted and well serviced a couple of years ago, and painted... So it is easy to spot this corrosion around coolant tank. I do not remember what it looked like before lifting engine for a spring clean. But it seems I need to pay attention to something. Does anyone know how to remedy / stop future corrosion as shown in photos? Thanks. BTW no problems with overheating and coolant was new last season. Looks like aluminium on steel corrosion.

 

[KompetentKrew]

It's not seawater escaping the hose?

 

[peteK]

You have a leak.

 

[Star-Lord]

You have a leak.

Ah... a leak makes sense. thx.

 

[Star-Lord]

It's not seawater escaping the hose?

It seems this could be the case. I check engine bay every hour or two when motoring... never seen any water and obv too hot around there to feel under way. But a small leak makes sense. I was thinking it could be a lot worse.

 

[KompetentKrew]

I think the barest dribble of salt water would be sufficient to cause that corrosion.

The metal will be iron or steel, and salt water is more corrosive than fresh water; the engine was repainted, so the finish will have been imperfect and the corrosion will have started in a pit.

I think, but I'm not sure, that the white is the salt left behind from evaporation of the leak. I think you only see the "white rust" around the raw water hoses. The leak is such a small amount of water you'd never notice it.

I would order a new hose and jubilee clip - I recently had a leak a bit like this, and the jubilee clip wouldn't fully tighten; the thread sort of jumped as it got nearly tight enough, and then it was one turn too loose again. You put boiling water on the hose to soften it enough to get it off, but the old hose may have perished whilst on there - if so it'll stick and will be damaged by the removal.

I can't properly see the spigot but, if the boat is being unused over the winter, you may be able to remove the casting and repaint it, should you wish.

I wouldn't let it worry you. My boat's engine is only a few years older (1994) but has far more corrosion - some of it like this, and "fresh water rust" in other places.

 

[rotrax]

That

It's not seawater escaping the hose?

That is EXACTLY where I would look first.

 

[Star-Lord]

I think the barest dribble of salt water would be sufficient to cause that corrosion.

The metal will be iron or steel, and salt water is more corrosive than fresh water; the engine was repainted, so the finish will have been imperfect and the corrosion will have started in a pit.

I think, but I'm not sure, that the white is the salt left behind from evaporation of the leak. I think you only see the "white rust" around the raw water hoses. The leak is such a small amount of water you'd never notice it.

I would order a new hose and jubilee clip - I recently had a leak a bit like this, and the jubilee clip wouldn't fully tighten; the thread sort of jumped as it got nearly tight enough, and then it was one turn too loose again. You put boiling water on the hose to soften it enough to get it off, but the old hose may have perished whilst on there - if so it'll stick and will be damaged by the removal.

I can't properly see the spigot but, if the boat is being unused over the winter, you may be able to remove the casting and repaint it, should you wish.

I wouldn't let it worry you. My boat's engine is only a few years older (1994) but has far more corrosion - some of it like this, and "fresh water rust" in other places.

Great info, many thx.

 

[VicS]

It seems this could be the case. I check engine bay every hour or two when motoring... never seen any water and obv too hot around there to feel under way. But a small leak makes sense. I was thinking it could be a lot worse.

There seems little doubt that seawater is leaking from the joint between the hose and the heat exchanger

I wonder if this is being made worse by a restriction of the water injection point into the exhaust causing a pressure build up in the seawater system
When was this last inspected/ cleaned?

 

[peteK]

There seems little doubt that seawater is leaking from the joint between the hose and the heat exchanger

I wonder if this is being made worse by a restriction of the water injection point into the exhaust being restricted and causing a pressure build up in the seawater system
When was this last inspected/ cleaned?

Good point Vic you may be right.

 

[Star-Lord]

There seems little doubt that seawater is leaking from the joint between the hose and the heat exchanger

I wonder if this is being made worse by a restriction of the water injection point into the exhaust causing a pressure build up in the seawater system
When was this last inspected/ cleaned?

The hoses were removed and replaced twice because the first chap who lifted out the engine was not as good as the second chap (long story) and on closer inspection of hoses and fitting - could be better. Ends of hoses are not in the best of shape and I have spotted the beginning of corrosion on another one. If the hoses were taken of incorrectly this may have damaged them.

To my knowledge 'it' has never been inspected / cleaned. I have no idea how to check this but now I will be able to ask a mechanic to check 'water injection point into the exhaust' and hopefully he can show me the details.

I wanted to give mechanic as much information and help as possible before call out (actually still at anchor in sunny Sardinia just so all bases are covered.

All the suggestions are much appreciated.