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Old 10-08-2010
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Winterizing a Yanmar 2QM20H raw water cooled

I am tired amd grumpy. The boat came out of the water Tuesday and it is seven months until launch. I have been working every day getting her ready for the BIG SLEEP. The BIG COLD SLEEP.

So, don't even answer this if you live south of Boston or anywhere else it does not get to 20 below for too long at a time in the winter.

I need to put -50 anti freeze (I use the plumbing stuff becauso it is way better for the environment) into the engine. I have to either run the engine until it gets hot enough for the thermostat to open, or do something else.

If you have a Yanmar 2QM20H and live were it gets really cold (see above), what do you do?

Thanks

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Last edited by rikhall; 10-08-2010 at 05:59 PM. Reason: typo
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Old 10-08-2010
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I run a hose into a bucket, and put the raw water hose in the bucket. Run the engine for a few minutes untill good and warm. Let the water run out of the bucket, (with the engine running) and pour in a couple gallons of antifreeze . Let the engine suck up that anti freeze and let it run dry for 15 seconds. Shut off the motor. My Yanmar has a drain valve, that I open to drain out the block. it's also a good idea to remove the impellor for the winter. Also you should change the oil now.

Some people spray fogging oil into the intake at the last. it's not a bad idea to tape up the intake and exhaust ports.
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Last edited by okawbow; 10-08-2010 at 09:36 PM.
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Old 10-08-2010
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Second what Okawbow said... Might be a good idea to leave the NEW IMPELLER someplace really obvious... so that you can't forget installing it in the spring.
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Old 10-09-2010
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The 'key' here is to be sure that the engine internals are FULL of antifreeze. If any section of the engine has AIR instead of antifreeze, such will promote 'slab rust' and that's highly destructive.

Best is run the hell out of the engine for a few hours to 'heat soak' the engine so that you build up a good layer of 'black' rust (ferrous oxide) in the water passages which is protective, then cool down and add antifreeze. Never ever store a marine engine 'dry' from the winter.

;-)
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Old 10-09-2010
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Just because the engine is "up to temp" it in no way means the t-stat was fully open especially if at a dock idling with no load on it. T-stats open and close quite a bit and those temp springs are nearly always in movement unless at or near full load and pushing up against max design temp/flow etc. which may or may not happen at idle with no load. Unless you absolutely know the t-stat was open I would not risk it. Pulling the t-stat is good practice.

If the t-stat not fully open then the antifreeze can just by-passed the block and still come out the exhaust. I have seen many a RWC engine that froze due to improper winterizing. The only sure fire method to know you got full circulation of the antifreeze is to remove the t-stat, reinstall the housing without. it and run the engine. This is fairly standard practice when winterizing a RWC engine.


On the 2 GM10 the coolant path looks like this

Path 1: Seacock, raw water pump, bypass junction, injection elbow of exhaust

Note: There is ALWAYS water flowing out the exhaust on this engine despite the orientation open/closed of the t-stat. So just because you saw coolant out the exhaust does not mean it went through the block.

Path 2: Seacock, raw water pump, bypass junction, engine block, cylinder head, t-stat, exhaust injection elbow.

If the t-stat is not open the cooling water completely bypasses the block and flows straight to the exhaust. The water delivered from the RW pump is basically branched into two directions at the cylinder intake coupling which is nothing more than a tee fitting. One side goes direct to the exhaust, so you don't melt the hose waiting for the t-stat to open, and the other goes into the engine & when the t-stat opens and allows flow to cool it. T-stat not open or only partially open means no or only minimal flow through the block.
Also what type of antifreeze wil you use? Propylene glycol / (PG) should not be diluted so be sure to sick enought through. You may also want to use the -60 or -100 PG stuff that is intended for engines which has a better anti-corrosive package in it. It is usually blueish or purple.

While you MAY sufficiently protect the engine without pulling the stat you also MAY not. Do you like going to Vegas?? Are ya feelin' lucky??

One trick I use on the RWC 1 & 2 GM's is to pull the stat then pinch the hose between the block inlet Tee and the t-stat housing using a pair of needle nose vise grips. This ensures that the the antifreeze I am pumping will NOT take the path of least resistance and flow direct to the exhaust. The pinching of this hose FORCES the antifreeze to flow through the cylinder block and head BUT only with the t-stat removed. DO NOT pinch this hose with the t-stat in place or you could melt your exhaust system!

In theory draining an engine SHOULD work but it still has a decent failure rate and a high potential for internal rust, especially on a RWC engine.. After working in three different NE boat yards I have yet to come across one who is willing to drain engines as standard practice for winterization, unless it is an outboard. Even in fresh water systems my yard makes you sign a waiver if you want your system "blown out" because it has proven to be unreliable on many boats especially ones with large domestic plumbing systems.

Marine engines often sit at odd angles, have drains at that are not at the bottom of the coolant passages, do not capture all the water in the block nor drain it and thus some can still freeze up when drained. While some engines do drain well many don't. Take the M-25 / Kubota for example this popular engine has multiple locations from which one could drain off the block yet you still don't get it all. I have flushed many of these engines and even after a thorough draining there is still a lot of dirty antifreeze remaining which on a RWC version would be fresh water that could freeze.

Pulling freeze plugs can often get more but this is the last thing you want to do on a rusty old marine engine as they will rarely if ever re-seal even with new freeze plugs. They can also be next to impossible to remove/re-install with the tight conditions on a boat.

Pulling a t-stat on a RWC engine takes about four minutes and on a RWC engine it is a good idea to replace it yearly anyway if it is not in good clean shape. I pull mine every other winter because I replace the antifreeze bi-annually. I prefer to flush my engine without the t-stat in place as it makes it far easier.

Over many years I have seen some serious crud buggering up RW t-stats as raw, dirty ocean or lake water has to pass through the t-stat, & block, to make it out of the engine. Normally I replace them. Engines are very expensive so it pays to winterize them well. Properly filled with the right mix of antifreeze I have never seen one freeze. I wish I could say the same for "drained" engines. The 1GM is an engine that actually drains somewhat well, better than many, but I have seen some installations that I would still feel quite uncomfortable with even IF you ignore the high potentials for rust internally.

Even if you own a FWC engine that has a HX you should test the antifreeze in the block to make sure it will not freeze. I have also seen numerous examples of boaters who did not know they had a leaking HX, one just last weekend. The leaking HX diluted the engine antifreeze and the engine froze in the winter. A one minute check with an antifreeze tester, before putting her to sleep, will tell you if you are safe for winter.

Tried to winterize a neighbors CD last weekend and her engine block antifreeze had a burst point of 5F. It was highly diluted and very light green. I circulated fresh antifreeze, just in case it freezes over the next few weeks, but I have not had a chance to pressure test her HX. I suspect that this is the culprit. Once the leak is defined, & I fix it, her engine will get a full Rydlyme flush, fresh antifreeze, t-stat and a new HX, or whatever is causing the dilution, then will then be put to bed. If I had not checked the condition of her antifreeze she'd have likely frozen the block and at the least blown out the freeze plugs which would require removal of the entire engine on this boat to hone the plug holes and replace them. Surprisingly leaking HX's on older engines are not very uncommon..

I have seen many, many ruined marine diesels from improper winterizing, hydrolocked and frozen mostly. Just this past spring the guy five boats away from me had two spit freeze plugs. A RWC engine which he sucked only one bottle of -50 into. The engine was full of raw water in the spring and two less freeze plugs indication that the t-stat was not fully open when winterized.

Watched another guy split his HX and refrigerant HX due to dilution of the antifreeze, again only one bottle of -50 PG that got to diluted. Have seen "drained" blocks split and freeze plugs blown out etc. etc.. Freeze plugs rarely go back in without leaking in the future and often require a R&R of the engine to replace which is a LOT more money than another one or two bottles of antifreeze and procedure know to work well...

Probably a lot more than you wanted but it is fall and others may be reading as well..
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Last edited by Maine Sail; 10-09-2010 at 03:38 AM.
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Old 10-09-2010
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Quote:
Originally Posted by Maine Sail View Post
Just because the engine is "up to temp" it in no way means the t-stat was fully open especially if at a dock idling with no load on it.

Probably a lot more than you wanted but it is fall and others may be reading as well..
Perfect! Absolutly perfect. I am not a mechanic by trade, but I can read and I spent some time with the service manual last night. It is so good to have ones thoughts and ideas confirmed. I had come to the conclusion that I would have to pull the t-stat and do it that way. Pinching that line off the top of the t-stat is something I never thought of.

Everybody says - get it "up to temp" Ya, right - what is "up to temp" anyway? There is no temp gauge and my 2QM20H runs really cool. My laser digital temp meter was only showing 60 F after 20 minutes of running at 2000 RPMs. But, no load. Hard to get a load when the boat is on the hard.

So - to do:

Pull t-stat, pinch hose, run with a bucket of water for a while, when bucket gets almost empty pour in anti-freeze and keep adding until I see it coming out the back as pure anti-freeze. (Any hints on pulling that off - not something I have done yet on my engine - and what about a gasket?)

Pull impeller

Check both zincs

Cry til next May and we get to launch again.

Thanks Maine Sail, we really do have to hook up next summer when we get dwon your way (or you up our way) so I can buy you a beverage (of your choice).

Rik
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Old 10-09-2010
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On QM engines there is a rubber hose between engine block and collector cooling housing there the thermostat is. You can just undo the hose on one side and run the engine to get the antifreeze running through the engine block, Just collect the antifreeze from the hose into bottle, then reconnect the hose and run the engine little longer.
On another side it is always a good idea to check a thermostat to see of it is closing properly. Now it is as good time as ever.
while you are working in the area of thermostat it is good idea to check how much carbon buildup is in mixing elbow.
For me it always looks like this: "OK, since I have all this tools out, and I'm already placed my bulk into engine compartment, what else can I do here?"

So I'd unscrew a water inlet into mixing elbow and pock around with some wire.
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Old 10-09-2010
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I have a raw-water cooled 2QM15G, and I just drain it rather than filling it with antifreeze. Pull all the hoses off, and open up the drain cocks -- one on the side of the block near the oil filter, and one on the underside of the exhaust manifold.... then tend to the zincs (your antifreeze will just all drain out anyways when pull the zincs out...)
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Old 10-09-2010
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Originally Posted by rikhall View Post
Pinching that line off the top of the t-stat is something I never thought of.
Just don't pinch the line off the TOP of the t-stat that goes to the exhaust elbow or you won't get any flow. You want to squeeze the one between the by-pass and the bottom of the t-stat that would force flow through the block and through the t-stat housing then out the exhaust.. Should be a short length IIRC.
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Old 10-09-2010
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The bypass is probably a relatively long length of hose snaking up the outside of the front of the engine block, taking off from the front zinc -- at least that's the way it is on the 2QM15G, 'spect it would be similar on a 2QM20H(?)
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