Yanmar 2GMF Coolant change/flush

Jun 15, 2015
15
Hunter 31 Port San Luis
Hey there sailors.

Im looking to do a coolant flush and change on my 13hp Yanmar 2GMF engine. I'm not sure what type of coolant is in it currently but it def needs a flush.

Question, To flush I drain the existing coolant and fill with new stuff. Run the engine for a bit with the radiator cap off until I see steam then cut engine and drain again. Correct? I repeat this a few times if I wish right?

As for what coolant to use, is 50/50 prediluted long life coolant I can get from auto store sufficient? Any recommendations?

Thanks so much.
 
Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
It's pretty easy to do. Use your Yanmar 2GMF manual to see all the draining ports and drain into a bucket. from the auto store purchase a bottle of engine flush and read the directions and pour it in and run the engine for time on the bottle. after that drain again and add DEX-Cool 50/50 and your set to go. However, There's a bigger picture here. If you have a HOT WATER tank, that too has fluid in the lines too so you may want to drain the lines too! to make sure you get all the old fluids out.
2. Heat Exchanger - Facing the engine the small hose leading into the exchanger is the raw water hose into the exchanger from your RAW WATER pump. remove the hose and with a flashlight look into the heat exchanger and see how bad the tubes are. If you see a lot of white corrosion filling the tubes then its time to clean it.
3. Exhaust Elbow - Inspect and verify it doesn't have any cracks If you see one crack you must replace it right away. do not think well later..for it will BITE you big time for it did me. If the engine for any reason doesn't start on the third rotation then STOP! turn your raw water seacock off until you get it running the turn seacock open. By doing this you will prevent seawater backing up and going into your exhaust manifold that could cost a lot of money to fix.
4. Raw Water Pump - Use only RUN DRY Global impellers, not the black ones. Run dry allows you to run up to 15 minutes without water in the pump.
Hope this helps you! StarGazer II Pearson 303 #221 You also can look for info in the Pearson section.
Best regards.
 
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Jun 15, 2015
15
Hunter 31 Port San Luis
Thanks. Great info! We just installed a water heater but haven't connected it to the heat exchanger yet so will do the flush before doing that. Just learning about the raw water intake and am probably going to run barnacle buster through it. Have never heard of the dry run impellors, ill look into them. Thanks again.
 
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Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
Thanks. Great info! We just installed a water heater but haven't connected it to the heat exchanger yet so will do the flush before doing that. Just learning about the raw water intake and am probably going to run barnacle buster through it. Have never heard of the dry run impellors, ill look into them. Thanks again.
Hey, check out my water heater installation before you do yours. I installed a MIXING valve at the heater which allows you to adjust hot water out to your liking. A but also saves hot water burns and wasting water trying to get the right temp out.
Just turn on the hot and NO cold and gives me 110 deg out for even showers. My wife loves a shower so now by installing the mixing valve it turned out that my 6gal tank actually gives me 12gal of hot water with the valve.

 

RoyS

.
Jun 3, 2012
1,739
Hunter 33 Steamboat Wharf, Hull, MA
+1 on mixing valve. Also, you can order that same mixing valve with threaded hubs instead of the copper sweat fittings shown. Then you can screw in hose barbs or whatever.
 
Dec 19, 2006
5,809
Hunter 36 Punta Gorda
Just did it and drain old full with distilled water and ran engine 30 minutes and even used radiator flush in for 15 minutes and did this a few times and on my 3YM took 2 end caps off
and used gun rod cleaner in each tube of heat exchanger.
Nick
 
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Oct 22, 2014
352
Pearson P303 #221 RockPort Maine
Nick 1+ on the gun cleaning kit. Only took the front off and used gun kit with CLR! Changed rubber gaskets and poured CLR into all tubes let sit ~ 45 min. started the engine and watched it flushing out the exhaust.
Capt. Rob
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
...saves hot water burns and wasting water trying to get the right temp out.
+1 to Stargazer. Even full hot does not burn. An additional benny is I now have hot water on Sunday morning, having not used it all Saturday night. I should have done this a decade ago!
 

Bob S

.
Sep 27, 2007
1,771
Beneteau 393 New Bedford, MA
Definitely refer to your Yanmar manual. I also removed the two hoses at the thermostat and used a vacuum outlet to blow air through them to remove the coolant from the hot water heater. I used a garden hose to run fresh water through them before I flushed using distilled water. I always use the black impeller from Yanmar, there is an authorized dealer across from my mariner. I remembered reading some negatives on the Globe impellers a number of years ago. I can't vouch for them and don't know if they are any different today then they were 10 years ago so it's your choice. You may want to read these posts.

https://forums.sailboatowners.com/index.php?threads/globe-impeller-update.144334/#post-947339
https://forums.sailboatowners.com/index.php?threads/diesel-rated-coolant.196394/#post-1536961
 
Jun 15, 2015
15
Hunter 31 Port San Luis
Just did it and drain old full with distilled water and ran engine 30 minutes and even used radiator flush in for 15 minutes and did this a few times and on my 3YM took 2 end caps off
and used gun rod cleaner in each tube of heat exchanger.
Nick
Im curious, I just read a bunch of stuff and the manual and it doesnt seem to call for adding actual coolant rather than simple distilled water?
 

NYSail

.
Jan 6, 2006
3,048
Beneteau 423 Mt. Sinai, NY
Both my yanmar manual called for yanmar certified coolant..... gives a few brands that meet their specs. I use shell rotella elc which was recommended by a certified yanmar mechanic. Just distilled water will lead to overheating just like it would in your car.......

Greg
 

MitchM

.
Jan 20, 2005
1,009
Nauticat 321 pilothouse 32 Erie PA
might as well replace your thermostat when you have the whole cooling system apart...!
 
Mar 29, 2017
576
Hunter 30t 9805 littlecreek
I used those hot water lines to flush just attached garden hose to inlet and put out put in 5 gal bucket ran engine with fresh water flow till clear then ran another 10 min with fresh water flowing over side boat then drain and fill with anti freeze