Hi all, I'm new to this forum. Just wondering if anyone has experience with a raw water cooled Yanmar 2GM20. I'm looking at buying a yacht which has a 15 year old 2GM (raw) with 1200 hours on it. It's making me nervous about buying the yacht ($20K) knowing that a new motor in the near future could potentially double the price of the boat. Raw salt salt water and cast iron seems like a bad mix.
Any experiences greatly appreciated.
Hi Jimmy welcome to the forum. I know nothing about Yanmars, but I have a Bukh raw
water cooled engine that's cast iron. It's 30 odd years old and still going strong. So don't
worry about the salt water/cast iron mix. I was told that raw water cooled engines are
designed to be just that....raw water cooled......no worries.
Hi Jimmy
I have a 1984 built yacht with a raw water cooled 2GM (15 hp) which is a earlier version of a 2GM20
I am not sure how many hours on it as it does not have a hour meter fitted but i assume it has a few
Before i bought the boat a couple of years ago it had a cylinder head replaced due to corrosion but the bottom end is still original as far as i know
The engine has 2 anodes fitted in the cooling system to help prevent corrosion and these need to be checked on a regular basis and replaced when necessary
From what i have found on the internet a common problem with these engines is the water injection tube in the exhaust elbow cracks where it is fitted in the elbow and this allows sea water to leak back into the cylinder head corroding the head and so i assume this is what happened to mine
When mine starts (normally starts after cranking for a couple of seconds) it is a bit smokey initially for a few seconds but then runs cleanly and smoothly
It doesn't have glow plugs fitted so i think this would be normal for this engine
Regards Don
Donk probably the first injection stroke or two may not have fired so it puts out a little smoke as it starts nothing top worry about.
If your engine turns over and starts in the first few cycles is in reasonable order .When it takes 60 seconds plus on the starter a motor could do with a freshening up for me any way 
1200 hours its just run in
