Yanmar 2GM20F Exhaust Mixer/Elbow

[kiltym]

Originally Posted by Dulcesuenos

This is incorrect, they do have zinc on the block above and forward of the lift pump . They are Into the water/antifreeze jacket so they rarely fail. Verified this on a new old stock crate 2gm20f and a older replaced 2gm20f.

The 2gm20 has a zinc like you describe, but I am fairly certain there is no such zinc on the 2gm20f(c).

The specific engines we had were 2gm20fc-yeu. They also made a non yeu version as well but I don't think there is a zine in either fresh water cooled version.

More info: Replacing zinc on Yanmar 20M20F - SailNet Community

Would love to know the part number and would be happy to look it up in the parts diagrams.

[Dulcesuenos]

The yanmar dealers all say no it doesn't have one (probably because it's not really needed to replace on the F series) but the blocks weren't made differently. I have looked at 4 different 2gm20F from 1995 to 2005 and all 4 had the zinc above and forward the lift pump, right above the block drain kind of behind the drain on the heat exchanger. I challenge you to look at yours and then respond.

[kiltym]

Originally Posted by Dulcesuenos

The yanmar dealers all say no it doesn't have one (probably because it's not really needed to replace on the F series) but the blocks weren't made differently. I have looked at 4 different 2gm20F from 1995 to 2005 and all 4 had the zinc above and forward the lift pump

Can you take a photo of the zinc and location and post it here? I am indeed curious as to what you have found.

There is no part # for a zinc on the F as far as anyone knows, including Mack Boring, likely the largest Yanmar dealer in the U.S. Even if there is a zinc as you state, and it was never needed to be replaced, there would still be a part # for it.

Here is the parts diagram, in Fig 1, page 5, line item 18, there is a ZINC, 27210-200300, clearly stating it is not on the F engines, only on the 2gm20.

You will note line 19, a "plug" which is there instead.

http://j30.us/files/Yanmar-2GM20-Parts-List.pdf

[Dulcesuenos]

Here it is. Same spot on 4 I've seen.

I will say I pulled one out of a 5100 hour engine that had probably never been replaced and it was still mostly there due to being in coolant not seawater.

[roverhi]

The exhaust on my 3GM30F is a cast exhaust fitting bolted to the heat exhanger with a vertical piece of threaded galvanized pipe to a cast iron mixing elbow. This type of fitting isn't an issue other than they can clog up after many hours of use. The length of pipe isn't critical for engine performance but may be for backfilling depending on your installation. Apparently yours could use the stock Yanmar cast fittings with close nipple to get the same functioning as your SS mixing elbow. Has anyone suggested that solution to you.

FWIW, stainless steel apparently doesn't like corrosive exhaust mixed with vibration which is what your set up has in spades. Westsail tried using a SS muffler with similar results to yours so went with cheaper stock exhaust systems that weren't stainless.

[kiltym]

Originally Posted by roverhi

The exhaust on my 3GM30F is a cast exhaust fitting bolted to the heat exhanger with a vertical piece of threaded galvanized pipe to a cast iron mixing elbow. This type of fitting isn't an issue other than they can clog up after many hours of use. The length of pipe isn't critical for engine performance but may be for backfilling depending on your installation. Apparently yours could use the stock Yanmar cast fittings with close nipple to get the same functioning as your SS mixing elbow. Has anyone suggested that solution to you.

I wrote this in a previous post:

"They make a forged version which is likely fine, but had no vertical room to accommodate it so we had to use the more standard, low profile, versions."

The forged version would not fit in our install unfortunately as no doubt it is the better solution.

The SS elbows worked fine for the 1.5 years we had them installed before selling the boat. But that was about 15 months longer then the stock Yanmars as they started leaking after 3 months or 50 hours.

[kiltym]

Originally Posted by Dulcesuenos

I will say I pulled one out of a 5100 hour engine that had probably never been replaced and it was still mostly there due to being in coolant not seawater.

You've got me. The parts catalog clearly shows it as a plug, not a zinc. Maybe they ran out of plugs and installed zincs in some units... Seems unlikely, but stranger things have happened.

All of it sounds odd to me, and I would not break a seal unnecessarily to find out so I guess it will remain a mystery.

[Wotname]

Originally Posted by kiltym

You've got me. The parts catalog clearly shows it as a plug, not a zinc. Maybe they ran out of plugs and installed zincs in some units... Seems unlikely, but stranger things have happened.

All of it sounds odd to me, and I would not break a seal unnecessarily to find out so I guess it will remain a mystery.

FWIW, all the GM series Yanmars that I have come across have that plug and inside the plug, there is a pencil zinc threaded in but I also know there is lot different parts out there for seemly the same engine.