Safety procedure after melted impeller on 2GM?

[patrickkidd]

I left the engine cooling water intake seacock closed and melted my impeller and overheated my engine. Yanmar 2GM, very low hours. Happened with the marina. Ran for maybe 7-10 minutes warmup at the slip and 7 minutes from slip before noticing the problem. Smelled exhaust from the cockpit and heard whistling and whining noises out exhaust pipe before the noises it suddenly settled back to normal but still with low amount of smoke coming from the engine. The impeller is disintegrated into little 2-3mm chunks in the pump.

After I replace the impeller, what other procedures should I do? I imagine all the little impeller chunks made it into the engine and exhaust? Any tips on what to do to avoid engine problems next time I'm rounding the Cape?

Cheers.

 

[Ralph Johnstone]

Only one thing to do ....................

Had a number of close calls where one of the crew grabbed the ignition key which was looped around the engine thru-hull but forgot to open said thru-hull because we just "had" to get going. Several other situations occurred over the years but someone always managed to catch it before any damage was done. Just plain lucky, I guess. Biggest problem of all is that the exhaust is a few inches below the water line. No indication if the water is flowing or not.

You're going to hear an assortment of the whackiest solutions to this problem but all they tell you is that your engine "has been running" without cooling water and you are now up "Schitt's Creek" without a paddle. Invest <$100.00 on a flow detector and you'll know instantly when water stops flowing and before problems start.

 

[MikeHoncho]

I had a inboard raw water cooled ski boat where the impeller failed with water. Following the impeller replacement I kept getting a mid RPM rise in temp issue. After messing around with the pump and checking things. I allowed the hose from the pump to the thermostat housing to drop into the bilge. Out came chunks of rubber and water. I also found chunks stuck in the outlet part of the pump where there was a strainer casted in the housing body. Lesson learned and problem solved. You didn’t say it was a 20f so I’m assuming you don’t have to worry about a exchanger. I’d disconnect as many hoses you can prior to starting it and try to get as much of the pieces out. I’d also check the nipple were the raw water is injected into the elbow. I had a clog there resent it from scale and crude. It is a choke point .

 

[sailcapt340]

Great advice from Mike and Ralph, you need to open up the pump and clean out the outlets (which you did ?) when you replaced the impeller. And flush out the hose to the thermostat.
I like the flow detector installation. It's a great back up to knowing the "sounds" of your engine while running.
My impeller has a stainless steel screw in the center that fits into a notch in the pump shaft. I once had a brand new, fresh out of the box, impeller that failed at the insert in the center with the screw. The rubber just spun around the insert. You couldn't tell be holding it, the insert was spinning but the rubber blades just stayed in place.
I'm telling you this story because it was the "sound" of the water coming out of the back of the boat that gave it away. It just didn't sound right and given that the exhaust in underwater there is no way to tell, except sound.
You should be fine but a real good flushing out won't hurt.

 

[jssailem]

what other procedures should I do?

Flush the system from the impeller to the exhaust. This will mean checking all of the hoses, removing them at the downstream end and checking for bits of impeller. Count the pieces and hope that you got all of them. Be cautious running the engine for a while. Check often for water out the exhaust. (like every 10-15 minutes of operation - It will encourage you to do more sailing). Monitor the engine temp and shut down at the first sign of temps higher then normal operating (somewhere around 155-185 depending on your engine specs).

If you really messed up the engine will eventually tell you. They are pretty tough engines and can take a little abuse. Just not constant abuse.

 

[markwbird]

The water from the raw water pump goes through the heat exchanger and then into the exhaust at the elbow. Nowhere else. I would recommend that you open up the heat exchanger and and clear out all the little bits of the impeller. Do the same for the hoses from the pump to the exchanger and then the exchanger to the elbow. That should cover it. As for preventing it, I never close that particular seacock for that reason. Also, I have gotten into the habit of always checking that water is coming out of the exhaust when I start it up.

 

[jssailem]

Also, I have gotten into the habit of always checking that water is coming out of the exhaust when I start it up.

Item ONE on the checklist
AFTER ENGINE STARTS:

1. Look over the stern and confirm exhaust water.
2. Advance throttle to 1000RPM. Confirm increase in exhaust water volume.
3. Listen for smoothing of engine sounds.
4. Check oil pressure.

 

[Sailfanatic]

My practice has been, if the engine is not ready to start, remove the key from the ignition and place it below in the chart table. The when you want to start the engine, if the key is not in the ignition, find it below and go through a check procedure to cover why it was there. i have for years have left the raw water seacock open and the key in the ignition, but that is a bit of a bad habit....

 

[Charles Erwin]

Monitor the engine temp and shut down at the first sign of temps higher then normal operating (somewhere around 155-185 depending on your engine specs).

This 2gm is probably raw water cooled. Likely it does not have a temp gauge either. Temp gauge or no - if raw water cooled then your running temperature ought to be about 105 F. I think the over temp alarm goes off at about 140 F with raw water cooling.

If raw water cooled then clear the hose between the pump and thermostat cover, remove the thermostat cover and the thermostat to assure no bits are lodged in the thermostat, then clear the hose between the thermostat cover and the mixing elbow - the discharge fitting at the mixing elbow is a favorite for impeller debris so check that is clear as well. Any debris in other places probably won't have any effect on cooling performance (ie motor block/head interior, mixing elbow, water lock muffler.)

I imagine you have fixed this by now but either way I hope this helps

 

[Sailfanatic]

This 2gm is probably raw water cooled. Likely it does not have a temp gauge either. Temp gauge or no - if raw water cooled then your running temperature ought to be about 105 F. I think the over temp alarm goes off at about 140 F with raw water cooling.

If raw water cooled then clear the hose between the pump and thermostat cover, remove the thermostat cover and the thermostat to assure no bits are lodged in the thermostat, then clear the hose between the thermostat cover and the mixing elbow - the discharge fitting at the mixing elbow is a favorite for impeller debris so check that is clear as well. Any debris in other places probably won't have any effect on cooling performance (ie motor block/head interior, mixing elbow, water lock muffler.)

I imagine you have fixed this by now but either way I hope this helps

This engine is fresh-water cooled, as you can see the heat exchanger in the photo. The OP needs to also open up and inspect the heat exchanger.

 

[Charles Erwin]

This engine is fresh-water cooled, as you can see the heat exchanger in the photo. The OP needs to also open up and inspect the heat exchanger.

Confused. Wish to avoid confusion.

Fresh water cooled 2GM is a rare animal indeed. The original post (to whom I intended to direct my comments) does not provide a photo. I did not see one from you either.

Is the 2GM original post (post # 1) motor raw water cooled?

Charles

 

[fullbore]

Yanmar model number should indicate whether or not is is fresh water cooled. Such as 2GM20F (where “F” indicates fresh water cooling). But raw water still pumps through exhaust mixing elbow.

 

[patrickkidd]

This is a 2GM, raw water cooled with no heat exchanger.

 

[Sailfanatic]

Confused. Wish to avoid confusion.

Fresh water cooled 2GM is a rare animal indeed. The original post (to whom I intended to direct my comments) does not provide a photo. I did not see one from you either.

Is the 2GM original post (post # 1) motor raw water cooled?

Charles

Sorry, I missed that the photo above was not from the OP...

 

[MitchM]

if your engine overheated, also check the integrity of hoses supplying oil to any oil cooler and your exhaust hose near the exhaust el. i had an engine overheat due to failed raw water impeller on my yan 3 JH4E which i caught pretty fast due to overtemp alarm screeching. impeller bits clogged the heat exchanger, took that apart and cleaned it. next time out i had an overheat due to failure of the formed oil cooler hose which started leaking... i had some extra oil and some repair tape on board that fixed it for the 5 weeks it took yan to send the special little weird hose part, (which was bigger on one end than the other of course. )

 

[HMT2]

This is a 2GM, raw water cooled with no heat exchanger.

Have one from 1983. It’s still running good

 

[patrickkidd]

if your engine overheated, also check the integrity of hoses supplying oil to any oil cooler and your exhaust hose near the exhaust el. i had an engine overheat due to failed raw water impeller on my yan 3 JH4E which i caught pretty fast due to overtemp alarm screeching. impeller bits clogged the heat exchanger, took that apart and cleaned it. next time out i had an overheat due to failure of the formed oil cooler hose which started leaking... i had some extra oil and some repair tape on board that fixed it for the 5 weeks it took yan to send the special little weird hose part, (which was bigger on one end than the other of course. )

You know, that's funny because I was just out on the first sail after repairing the impeller and discovered that I need to replace the exhaust hose. There is a slight leak there, and I recall it ballooning up a bit near the manifold whilst the engine was overheating. I am also looking forward to getting my new temp sensor in the mail this week, which happened to be on order when this happned! When it rains it pours, for both the good and the bad I guess.

 

[RoyS]

I do not hear high frequency sounds as well as most people and I am not alone in this. As people age many will lose their ability to hear high frequency sounds like the typical engine over-temperature alarm. I installed a boat horn near the helm connected to the engine over-temperature switch. That I can hear and so can the dead probably.

 

[DArcy]

@RoyS I've been thinking about doing this. I had an overheat a week ago due to the water pump belt breaking. I heard the change in engine RPM so was keeping an eye on the engine gauges. I saw the temperature creeping up and the light came on but couldn't hear the buzzer over the engine noise. I'm going to get a louder alarm but it will also go off when starting so didn't want to go too loud. I heard (probably on this site) of someone putting a momentary button in line with the alarm to hold it off during starting which sounds like a good idea then I can install the loudest 150 dB alarm I can find. I may need to change my shorts after it goes off but at least I will know if there is a problem
Maybe something like this mounted under the chart table

 

[RoyS]

IMHO you really do not need to have all your alarms so enhanced. Overheat is the one to watch. I placed a 12 volt marine snail horn in parallel with the overtemp alarm. The circuit consists of tapping into the hot wire on the ignition switch, going to the horn, and bringing the ground back to the engine overtemp switch. That switch completes the circuit to ground only when overheated and not when you are starting.