yanmar 3YM20 heat exchanger corrosion

[PauloP]

Hello,
I bought a oceanis 323 (made in 2006) some months ago. The boat is in very good condition. The motor is a yanmar 3YM20. This week I notice that there was a coolant leak near the heat exchanger. When I take out the tube, I saw this corrotion in the aluminium - photos. A friend of mine will open this part to weld the aluminium. I´m perplex with this. Is this comon? What is the cause? Will I have corrosion in other parts of the motor? The manual don´t refers any zinc in the motor.

[PauloP]

I forgot to say that the motor has 640 hours of use.
Does anubody can help me?

[Compass790]

I dont really know about yr 3ym20 but I remember reading in CF someone said that the tube bundle is cupronickel & the ends caps are aluminium & if they dont have a gasket seperating the differing alloys the end caps corrode badly. I searched but cant remember which post it was in. try the google custom search, it probably applies to 3ym30 too.
The poster had repaired quite a few but cant recall who he was either.

[Compass790]

apologies PauloP I might have the materials wrong.
Here is the thread you should look at tho. pay particular attention to Kenbos posts, he's clearly had to deal with this issue: Its not your engine but maybe the same issue.
Hope it helps.

https://www.cruisersforum.com/forums...d-60015-3.html


If it's any consolation to you I talked to a fellow sailor who had a similar problem on a low hrs Beta 20hp. Says they have changed the hx supplier now.
He had to threaten legal action to get them to replace it.

[DougR]

15 year old engine.....how many times has the antifreeze been changed?

Of course you can’t know, but most likely a lack of cooling system maintenance is the culprit here. Failure to change the antifreeze, use of low quality antifreeze, high chemical content water, maybe a thin spot in the casting to start with, all can lead to a failure like this one.

Repair or replace the housing and be meticulous about your ongoing coolant maintenance.