Overheating Yanmar 1gm

[TDudley]

I am sure you have heard this all before.

I have a warning lamp and buzzer indicating overheating.

I have replaced the Thermostat, impeller and tempeture sensor. I have checked hoses for blockage. I have checked to make sure water is coming into the boat to be used for cooling. I have water comming out of the exuast port. I dont have any odd smoke at all.

But still the same, after about 1 hour of motoring, my warnings come on.

I have not checked the mixing elbow, that will be next. My orinal impression was that my cooling system passages were all gunked up with crap because I dont have a strainer prior to sea water entering the system. I came to this theory because my cooling system flushing plug was PACKED full of crap (sand and small shells). To help try and clear it I tried flushing and I also would gun the engine when the warnings occured.

But I have come accross some other post that talk about having blown head gaskets that have casued these symptoms. I have a 2 Yanmar Manuals and a Parts book, but I cant find something specific call a head gasket. Maybe this is a nick name for something else? an someone answer this for me and whether it could have something to do with overheating.

Thanks,

 

[dakno]

I would try the mixing elbow, its a frequent source of cooling issues. The head gasket is between the engine block and the head and is a serious project to undertake.

 

[Neil McDonald]

The head gasket refers to the cylinder head. I would check quite a few more items before chasing this subject. The mixing elbow for one. They only last around five years in my area. Not sure if your engine is fresh or sea water cooled. If fresh water cooled I would take apart and clean the heat exchanger

 

[Benny]

Is the engine actually heating up? The warning lamp and the buzzer going off could be the result of a short in the wiring. On the h27 the electrical harness going from engine to control panel takes some turns around sharp fiberglass corners and with time and hull flexing that harness can get chaffed cutting through the wiring insulation and causing short circuits playing havoc with the warning lamps and buzzer or the key switch and starter button. Also check for a soft collapsing hose or debri in the cooling passages. Pieces of a previously failed impeller can cause intermitent cooling flow blockages.

 

[TDudley]

Thanks for the info. I will have 5 days to check it out and hopefully resolve it. I will post something when I get it fixed.

 

[J Hunter]

Of course check that the head/cylinder is actually getting too hot and not a false alarm, but I believe your issue is more likely before the pump rather than after it. The engine cross -sectional area of the engine jacket passages are bigger than the supply hose, and the mixing elbow is even bigger, the overboard hose even bigger. Not to say corrosion formed during lay up, or scale precipitated out by engine heat doesn't sometimes cause a restriction there, but more often I've seen and heard of sea suction fouling.

Do this test if you can, unhitch the water pump discharge from the motor and direct it into a 5 or six gallon bucket (close the seacock while doing this). Reopen the seacock and quickly start the motor and time how fast it fills the bucket to a line you draw about half way up. Shut off the motor and reconnect the hose to run the engine at idle for ten minutes to cool it, then let it sit another half hour to cool it off even more. Now close the seacock and disconnect both the pump discharge/engine supply connection and the sea suction at the seacock. Fashion a hose extension without any air leaks on the hose you took off the sea cock and put the end in the half full bucket. Put the pump discharge into another empty bucket, run the motor and if it pumps this water noticeably faster than the first bucket your problem is fouling at the sea suction. The fact that water appears to free flow from the sea suction with the pump suction disconnected can be deceiving. The pump is moving alot of water under pressure through a pretty small discharge hose and an unrestricted suction is the key.

As far as clearing it out if it's the trouble, that can be tough in the water. Pressure back flush with some descaler is often tried but rarely if ever works. Mask and underwater light and scraper another possibility. Haul out remove anti foul strainer plate and rod out always works.

One thing about the mixing elbow- if it's restricted, it slows the whole stream of water cooling your motor, meaning you can't have an overly restricted mixing elbow AND an adequate flow out the stern. Not to say that that is definitely not the offending restriction, only saying that some water getting to the stern does not prove pump suction is adequately clear any more or less than it indicates a restricted mixing elbow or engine passages.

My boat has a concave plate with slots at the hull covering the sea suction, maybe some of those shells you saw in your engine flush connection have built up there as well if yours is similar.

 

[TDudley]

Well, I think I found the problem. I blew a hole in the exhaust pipe that is between the mixing elbow and muffler while out with the Admiral and kids today. It put so much smoke in the cabin it reminded me of when Quint tried to pull Jaws into the shallows and blew his engine.

After restoring order to the crew, I found the hole and also saw that the pipe was about 50% clogged with carbon. It was also a piece of crap old ass pipe which I am still kicking myself for not paying more attention to and replacing. Especially since I brought more than enough of the $10 per foot pipe to bench test the engine a year ago but it was 400 miles away.

I put the crew to sailing and then wrapped enough electrical tape (all I had at the time) around the hose to reach from here to the moon. We then started her up and made a bee line to the slip. IT HELD. There were a few bubbles, but my god it held. I’m not even going to mention the engine stop pulling loose or the anchor falling off its holder…kids play.

I ended up getting less than 2 feet of brand new hose from WM. It was a 30 minute fix and I even ended up with a new fishing rod to boot (my seven year old lost the one I had as a part of the sacrifice for thinking we had just got torpedoed due to all the smoke). I think this was the root cause of the overheating issue. Tomorrow will tell. Thanks for the help and here is to the new roll of duct tape I have to save my bottom in the future. I even bought it in the color black so that no one may notice if I am between repairs.

 

[Neil McDonald]

Now I am really concerned about the condition of your mixing elbow!

 

[TDudley]

Yea, me too. If I had some gasket maker I would have checked it this weekend. I did take her out again and she motored fine. I had the overheating alarm come on after about an hour of running at 2500 rpm, but it went off almost immediately. I will check it. It may also give me an opportunity to look further up into the engine.

Any suggestions on how to clean a mixing elbow?

 

[Neil McDonald]

Most people replace them rather than to try cleaning them, so sorry have no suggestions. I suspect that you will have better idea once you have removed it. Good luck!

 

[dakno]

fyi- according to my mechanic- you should be able to touch your engine while running at normal operating temp- without burning yourself. I have tested this(do you really know if your overheat buzzer works properly), and have no scars to date.

 

[Steve Dion]

I suggest that you get a new mixing elbow & gasket. I think you may have a slightly different elbow than what they use on the 2GM & 3GM engines.

If you are lucky you can clean up the old one and have it as a spare for the future. Most of the time they are shot.

 

[TDudley]

Dakno,

Based on what your mechy said, I have passed that test. Just this weekend when it ran hot, I opened the engine drain plug to see if there was a clog there and had running engnie water spill over my hand. I was able to stand that water temp with very little problem.

I think I am going to replace the elbow, but I want to take it off and inspect it before I order a new one. I still am thinking that the plugged and kinked hose may have been most of my problem. When I bench tested the motor last year, I had lots of water out of it and I was not using that piece of crap hose at that time. I would fill up a five gallon bucket in no time. And I had no warning alarms occur.