Yanmar 1GM10 Cooling Water Issue

[PaulH]

Hello folks...I have a question in regards to raw water cooling on my 2001 Yanmar 1GM10...there's about 350 hours on it, and has been running exceptionally well with the exception of once when some water got into my fuel. That's when I started noticing that my raw water cooling light kept coming on after about 0.5 - 1 hour of running.

I had my fuel tank removed, and all of the water removed by a certified mechanic, the fuel system was primed as well. I would gather, though, that this would have nothing to do with my raw water intake.

I (myself) removed the impeller, and brought it to a Yanmar dealer to get a new one, and the guy told me that there was nothing wrong with the one I had in my hand...??? I replaced the impeller, and I still got the RWC alarm.

The raw water strainer is about 7 months old, and I keep a pretty good eye on it, and all appears to be normal.

Has anyone else had this problem, or have an idea of what could be going on? Any help would be GREATLY appreciated.

 

[Don S/V ILLusion]

Paul - is it the temp sensor light to which you refer?

Whoever told you the impeller was okay with 350 hours on it is an idiot!
Even if it appeared okay, that's FAR too long to run an impeller. Regardless of the hours as an indicator, one of the most common problems with cooling water is the impeller going bad but appears fine. What often happens is the brass spline and rubber hub separate slightly thereby allowing the brass spline to turn freely while the impeller blades don't move.
Your inclination is correct that this is the first thing to replace.

 

[kloudie1]

You have an interesting one, Paul. It could be a bunch of different stuff .. It would be interesting to know how you clear the light.. Do you stop the engine or do you slow it down to make the light go off?
Some of the things to suspect would be the strainer.. clean it.. the exhaust elbow could be plugged where the water goes into the exhaust pipe, the thermostat could have failed or plugged, a hose could be pinched, or the switch that turns the light on could be failed (unlikely) These are arranged in order of probability, I think.. There are many others but these are common .. it gets more difficult (and expensive) if you eliminate those and it is still misbehaving! Good luck !

 

[PaulH]

Don...yes, it's the RWC light that comes on, and an alarm goes off with it...I couldn't physically move spline, but that doesn't mean the engine couldn't...I will go get another one...

Claude...I've pretty much checked everything on your "list", and all appears normal. I normally just shut the engine off for about 0.5 hr, and start it back up again...I haven't taken any trips since I've noticed this happening, just in and around the marina...I'm not going to venture far until this is fully fixed...

 

[Stu Jackson]

It could also be something BEFORE the strainer, like the small thru hull opening. What we did was to blow out the hose with a dinghy foot pump, cleared the crud, whatever it may have been, out of the thru hull. Agree that 350 hours is a loooong time for an impeller. Anyway, when you had ti out, it was as easy to replace with a new one. The good news: now that you know how to do it, it should be a snap from here on out.

 

[Steve Dion]

Check intake prior to the strainer.
Check for hoses that may be collapsing.
Check the exhaust elbow.
Check the heat exchanger.

 

[Hermit Scott]

RWC

You say the light comes on after about 1/2 hour of running. The RWC light must be measuring temperature. IF you still have water going out with your exaust. I would guess that the thermostat is stuck in the closed position.

 

[kloudie1]

Yes, Scott is right.. Remove the thermostat and put it in a pan of water with a good thermometer.. raise the temp slowly until the port opens .. It should be close to the temp stamped on the device. The approximate opening temp is 107 F and it should be fully open at 125 F for this raw water cooled engine. . Remove the exhaust elbow from the engine and clean out the inside of the water injection point and the exhaust passage.. Certainly blow out the line from the strainer through the thru-hull..
Good luck!

 

[PaulH]

Scott...I replaced the thermostat about 3 months ago...I figured that was the problem because when I took it out, it was very difficult to move...so I tried the heating up water trick that Claude mentioned...and it didn't move. The new one I put in worked perfectly.

Could there be something wrong with the circuit itself? I mean, would a short cause the RWC light to come on...but then...one would think that it would come on right away...It's really getting aggrivating...as I won't go anaywhere until I get it sorted out...

I'm Puzzled!?!?

 

[Hermit Scott]

Temperature

The whole goal of the RWC system is to keep the engine at a specific temperature. Don't run it with out a thermostat, it's hard on a cylinder liner to have too cold of water on the other side of the combustion chamber. It's actually better for an engine to be ran hotter. However this is only possible with synthetic oil that doesn't break down at high temperatures and also you can not run it hotter than the boiling point of your coolant. Otherwise the coolant turns to vapor and there is no coolant up against the cylinder and it will overheat and fry something. You must have a thermostat set to run hotter, and it's better accomplished with a closed cooling system that can be pressurized.
Anyway, I just rebuilt a Yanmar YSM12. I installed a temperature gage right away and haven't even gotten around to installing the alarm yet.
Alarms are great, they let you relax a little and not have to keep an eye on stuff so much but in my opinion everyone should have a temperature gage and an oil pressure gage.

 

[kloudie1]

More intrigue, Paul.. If the thermostat was bad and it overheated a few times, you may have a pretty good amount of crud built up in the cooling passages in the head and block. Overheating the salt and little critters inside can rapidly build up stuff that is difficult to get out.. Have you tried hosing backwards through the engine? Like remove the injection hose from the exhaust elbow and remove the pump outlet hose (jump the pump with a hose connection to the thru-hull) and pressure water through the system from the injection hose out the thru-hull hose.. May help. There are some chemicals to remove salt and crud that can help with this too.. it may be in order to remove the thermostat for this flush, since it would reduce flow.. ?? I remember seeing a discussion on the forums about a good way to flush a raw water cooled engine. There were some chemicals listed to help with this in that discussion. Again, I hope this helps..

 

[PaulH]

Thanks for all of your help guys...I really appreciate it...I guess I have a few things to try...

Scott...alarms are great...until they go off incessantly...and I don't know if you're familiar with the alarm on the 1GM10 system on Lancer's...it's something like the squeal of bad brakes, with a dash of volume for good measure!!

Once again...thanks for the suggestions.

Cheers

 

[Tom Metzger]

I didn't see where it was said the engine was actually running hot. Is it?

Is the amount of water in the exhaust normal?

Is the belt tight on the pump?

Is the impeller installed for the correct direction of rotation?