I thought I would do this post in the hope that it may save someone else the trouble I have just had to deal with. They say ignorance is bliss- but it can also become VERY expensive! I am manic about maintenance on my boat having the engine professionally serviced every year. This year, I had noticed that the end caps on my heat exchanger manifold were showing the slightest sign of corrosion. There was a tiny white line at the joint between the manifold and the end caps at each end. I had ordered the new seals ( O-rings (from Yanmar) and pointed it out to the mechanic. When he removed the end caps- the one at the back of the engine - where the sea water enters the manifold had actually corroded the seal surface on the aluminum manifold and was very close to blowing out. I removed the manifold and found that unfortunately this corrosion looked to go about 3>5mm into the aluminum at the sealing surface. When I found a replacement manifold from Yanmar was going to cost $3900, I got serious about trying to get it repaired. luckily I did find a guy who was willing to tackle the job and had a big enough vertical mill to be able to re-machine the seal surface after welding. Well, it turns out he had to grind out as much as 30mm ( over an inch) of metal before he found solid aluminum that would receive the weld. It turns out , once corrosion begins it permeates into the the aluminum much deeper than it appears to the naked eye.
During this process, I found out that you really should replace these O'ring seals every 12 months- it turns out this is the cheapest possible way to avoid this problem- you have bronze end caps clamped to an aluminum manifold , exposed to salt water- not at all good. Having said that, in 6 annual engine services by registered Yanmar mechanics, I don't think anyone of them checked - let alone replaced these seals. I was also advised to use copious amounts of Vaseline grease on these sealing surfaces during re-assembly.
I also found that my fresh water drain plug at the bottom rear of the manifold had become blocked with a build up a dirt/sediment- it was easy enough to clear and clean, but again who would have thought! Another good find was that instead of paying $20 for the genuine Yanmar O'rings , a standard 232 O'ring is a perfect fit and readily available anywhere that stocks a good wide range of O'rings (it is 76mm x 3mm thick) and costs cents each!
So , I hope this post saves someone else from experiencing this same - potentially ,very expensive problem.
During this process, I found out that you really should replace these O'ring seals every 12 months- it turns out this is the cheapest possible way to avoid this problem- you have bronze end caps clamped to an aluminum manifold , exposed to salt water- not at all good. Having said that, in 6 annual engine services by registered Yanmar mechanics, I don't think anyone of them checked - let alone replaced these seals. I was also advised to use copious amounts of Vaseline grease on these sealing surfaces during re-assembly.
I also found that my fresh water drain plug at the bottom rear of the manifold had become blocked with a build up a dirt/sediment- it was easy enough to clear and clean, but again who would have thought! Another good find was that instead of paying $20 for the genuine Yanmar O'rings , a standard 232 O'ring is a perfect fit and readily available anywhere that stocks a good wide range of O'rings (it is 76mm x 3mm thick) and costs cents each!
So , I hope this post saves someone else from experiencing this same - potentially ,very expensive problem.
