Yanmar 2GM water passage cleaning

Nereussailor

Nereussailor

.
Mar 22, 2004
733
Hunter 30 Vero Beach
I finally got my Yanmar 2GM engine out for some needed repairs and started taking it apart. Behind the plate for the zinc in the back of the head there was a lot of black stinky residue. I couldn't see inside the water passage in the head. I carefully scraped around in there and got it so that I could see in more than an inch or two but I need to know the best way to get it cleaned out completely. Has anyone ever done this without tearing the whole motor apart?
 
woodster

woodster

.
Sep 15, 2009
6,244
S2 9.2a Fairhope Al
you may need to take the head off and boil it out with muriatic acid and do a valve job while you have it out ...i know you don't want to do that but that is the only thing i can think of that will get it clean again ....you can prolly get the valves ground for about 100.00 dollars.....if it a two cylinder....just get a automotive machine shop to do the valves i think its a 45 degree grind on the valves and seats
 
Nereussailor

Nereussailor

.
Mar 22, 2004
733
Hunter 30 Vero Beach
Thanks woodster, I just heard that that was the best way to do it about an hour ago. I was hoping not to have to pull the head, but oh well, it's only money. :)
 
woodster

woodster

.
Sep 15, 2009
6,244
S2 9.2a Fairhope Al
the only thing i have reservations about this is ......if it is corroded very bad inside it may be to thin.....try taking an ice pic or some sharp object before you have it boiled out while you have it on the workbench and try to pick it some more until you cant get any more of that crud out and see if it will be open enough to use as it is....then you may get away with just a head gasket and some cleaning just go slow and cautious
 
Nereussailor

Nereussailor

.
Mar 22, 2004
733
Hunter 30 Vero Beach
It's not plugged completely, I have taken a coat hanger carefully poked it around in the head and got most of it out. It seems like it was mostly within an inch or two of the zinc end. I pulled one of the freeze plugs in the back of the block to see if it was plugged in the bottom half. The bottom half looks pretty good. The black stuff in the block can't be more than 1/32" thick. I hooked up the shop vac and sucked out as much as I could through the zinc plate in the back of the motor and through the thermostat housing, then swapped the hoses and made it into a blower. I could feel a good stream of air out all of the open holes, so I think it's going to be okay. It's a lot better than it was before I cleaned it out and it never overheated.
I've never understood how Hunter could put in a sea water cooled engine and not put in a sea water strainer. I'm planning on putting one in when I put the engine back in.
 
woodster

woodster

.
Sep 15, 2009
6,244
S2 9.2a Fairhope Al
the strainer will keep out the seaweed and the like but it will not stop the degradation of the block ...that is what the zinc is for and its best to maintain them ( checking and changing them ) probably more so than the water pump impeller
 
Nereussailor

Nereussailor

.
Mar 22, 2004
733
Hunter 30 Vero Beach
The block is really solid, I don't see any loose rust or eroded metal, more of a buildup of stuff that looks like black rock salt in most places and some black goo in others. For as old as it is, it looks to be in really good shape which I wasn't expecting.
 
Ted

Ted

.
Jan 26, 2005
1,278
C&C 110 Bay Shore, Long Island, NY
You can try circulating white vinegar through the block and head as if you were winterizing the engine. On the 2 GM remove the thermostat then pinch the hose between the block inlet "T"and the thermostat housing using something like a pair of needle nose vise grips. This ensures that the the vinegar gets into the block and head. Let it sit for a few days or a week. Then flush with fresh water and repeat as necessary. The white vinegar is pretty mild so it takes some time to work.
 
S

Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Star Brite makes a descaler that is supposed to remove sale and corrosion.

Are you sure that this engine is raw water cooled? Most of the GM's are fresh water cooled with a heat exchanger. If you use antifreeze then you have a fresh water cooled engine (closed loop).
 
Nereussailor

Nereussailor

.
Mar 22, 2004
733
Hunter 30 Vero Beach
I wish it was fresh water cooled. Life would probably be a lot easier. No antifreeze and a short L shaped exhaust elbow. I've got it pretty clean right now and will flush the inside out with a garden hose to get rid of any loose particles floating around. That will also give me an idea of how much flow there is. once that's done it's time to start putting everything back together.

Does anyone know of a good Yanmar parts dealer here in Florida? I used to use Marine Diesel Direct when I lived in Wisconsin. I'm not in their territory anymore. The local Yanmar parts guy is really slow here. The last bunch of parts I ordered from him took a couple of weeks to come in and he shorted me all of my crush washers. We used to have a Yanmar dealer right here in Vero Beach that was really good, but they went out of business a couple of years ago.
 
woodster

woodster

.
Sep 15, 2009
6,244
S2 9.2a Fairhope Al
Nereussailor said:
Does anyone know of a good Yanmar parts dealer here in Florida? I used to use Marine Diesel Direct when I lived in Wisconsin. I'm not in their territory anymore. The local Yanmar parts guy is really slow here. The last bunch of parts I ordered from him took a couple of weeks to come in and he shorted me all of my crush washers. We used to have a Yanmar dealer right here in Vero Beach that was really good, but they went out of business a couple of years ago.
Click to expand
try masty in clearwater or bells marine in p cola
 
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