Yanmar 3GM30 over heat

[Mazenaziz]

Thanks everyone for the help here. Here is an update and what I did this morning. I took off beginning of every hose and blow in it to make sure there is no blockage somewhere. Then topped every hose with coolant manually. Some of them specially the top ones off the engine block did have bubbles coming out as I was pouring coolant. Anyways engine has been running now for almost half an hour. Temp staying around 150. And little high rpm. About 2000? Please know that none of the gauges work on mine. That’s the next task. So for now just going off sense, alarm sender(new) and I bought infrared temp gun. Fingers crossed it stays like that without over heating and I think I would have solved the problem. If so, blue smoke would be my next worry. Prob something I messed up during this process.

1-the coolant good stuff is that you wanna look for the pink oat premium coolant. Different than the winter antifreeze

2- my 3gm was adjusted to be coolant cooled. All the parts are from local shops unfourtanetly and doesn’t have a bleed air valve anywhere. All the hoses now are staying way cooler than the last few days. Even the ones after the thermostat, are warm not HOT.

[NYSail]

Shell rotella extended life after flushing extensively. I like to first remove the thermostat and flush several times..... this way you don’t have to get engine heated up. I also fill without thermostat and make sure heat exchanger hoses for water heater are filled..... then I put thermostat on and button her up. Also as was mentioned check the exhaust elbow. My previous boat had 3HM35f..... I always ran her hard and I’m the 10 years I owned her I changed the elbow twice. First time the water
Port was 80% blocked. Second time the exhaust side was almost completely coked. Some people clean them..... I just change them.

Good luck!

[Mazenaziz]

Thank you nysail. Why is the elbow related to the coolant? Or you just mentioning to check in general. Yes agreed, I don’t have heated water installed on mine but yes the empty coolant hose thing was weird. Fingers crossed now. Any thoughts what to check now Inregards the blue smoke?.

[Compass790]

Originally Posted by Mazenaziz

Thank you nysail. Why is the elbow related to the coolant? Or you just mentioning to check in general. Yes agreed, I don’t have heated water installed on mine but yes the empty coolant hose thing was weird. Fingers crossed now. Any thoughts what to check now Inregards the blue smoke?.

Blue smoke is not a good sign after overheating. Usually it indicates wear in piston/rings/bore or valve guide area but engines can smoke for decades.
I'd first change the oil & filter as you might have "cooked"the oil & that can smoke more.
If it starts quickly from cold & runs ok with good oil pressure I wouldnt worry too much if oil consumption is not too high.
If it is hard to start I'd think about compression or leak down test then.
Check cooling elbow as they are prone to clogging. If it's knackered you can buy cast ss ones cheaper. Wont cause blue smoke but black smoke.
You need gauges & alarms

[NorthCoastJoe]

If I understand this right it was a raw water cooled 3gm30 that was converted to freshwater cooling. First place I would look is the thermostat, then exhaust elbow. If you have a dead heater hose looped you can get rid of it and plug the ports, if I remember right 3/8 brass pipe plugs fit. All the ports are standard pipe thread.

I would change the oil and filter its only 3 quarts. Run it and work it see how much smoke you get after a little use. Most of the time you can live with some smoke it is not too much.

I have rebuilt some raw water cooled engines and they can have quite a build up of crud in the water jacket, how long ago was it converted to freshwater cooling? Who did the work, and did they clean out the water jacket?

[Cpt Mark]

To bleed the engine, any engine, find the place where the air rises the highest and crack it open there and fill and bleed. On my 3gmy30 that is the hot water heater for my boat which is pretty typical on cruising boats.

When mine was new to me the PO did an inept job with the coolant as evidenced in that it was everywhere outside the engine. gave me fits with random overheats for weeks before I finally got all the air out of it.

[chasfgr]

Originally Posted by Snowgoose71

Is your thermostat working properly?

To check, take it out heat it from closed in an electric kettle, using a liquid thermometer.
It should be fully open just above 80C.
With your history, I'd change it in any case, keep the old, if good as a spare.


Raw water cooled engines are usually the worst.

[NYSail]

Originally Posted by Mazenaziz

Thank you nysail. Why is the elbow related to the coolant? Or you just mentioning to check in general. Yes agreed, I don’t have heated water installed on mine but yes the empty coolant hose thing was weird. Fingers crossed now. Any thoughts what to check now Inregards the blue smoke?.

If the mixing elbow begins to get blocked it can cause an increase in back pressure in the engine as well as reduced sea water flow circulation and for exhaust cooling.

Greg

[gamayun]

I was just reading another post on a Facebook page that said they had a belt slipping that wasn't turning the water pump and overheating the engine. I'm just grasping at straws here and passing this along in case it might of help.