3YGM 30 Overheat Alarm

Halo

Halo

Well-Known Member
Joined
10 Nov 2009
Messages
2,051
Location
Wetherby
Visit site
Dear All
I serviced my 3YGM30 2 weeks ago - changed coolant, seawater pump impeller, oil, filters etc. Took her out for a motor in the flat calm last weekend. I ran her flat out for 5 minutes after warming up etc and the obverheat alarm came on. Idled her for a short time then switched off. Left her 10 minutes then motored in - all well. Plenty of raw water going through and no lack of coolant. any ideas about what could have caused this and what checks to make.
Thanks in advance
Martin
 
3YGM30 Overheat Alarm

Could you have picked up a plastic bag on the raw water inlet, then stopping the engine the bag could have dropped off and was well again?

Were you reaching maximum revs (3600) when at full throttle? If the propeller is heavily fouled, you can have the throttle fully open but not reach max revs, then after a while the engine overheats and alarms...... it happened to me once with a Volvo.

Alan.
 
I have the same engine, but new and trouble-free at the moment (crosses fingers, touches wood, throws salt over left shoulder). Not that I'm suspicious.

My old engine (different make) was very fond of spurious overheat alarms, as well as genuine ones. Usual causes in no particular order - faulty thermostat, faulty temperature sender, lead coming off temperature sender, vegetation in raw water filter, animal life in raw water filter, forgetting to turn on raw water sea cock.
 
A batch of the original 3YM30 engines had an overheating problem that showed up when operating at full throttle / high sea water temperature due to lack of cooling tubes in the heat exchanger. My engine was one of the affected ones. This was brought to our attention by Fullcircle.

I quoted the serial number to the supplier and they sent out a new up rated cooling coil
free of charge.

This problem was known by Yanmar, but they would not notify owners and automatically change the coil. Few years back now, so not sure you would get a new coil free of charge at this stage if your engine is one of the affected ones. Best to check / quote engine serial number to supplier, your engine may already have the up rated coil fitted. If it has - all advice above is good.

Bob
 
alan said:
Could you have picked up a plastic bag on the raw water inlet, then stopping the engine the bag could have dropped off and was well again?

Were you reaching maximum revs (3600) when at full throttle? If the propeller is heavily fouled, you can have the throttle fully open but not reach max revs, then after a while the engine overheats and alarms...... it happened to me once with a Volvo.

Alan.
Click to expand...

It also happens with Beta engines too, especially when you move to a new berth and finally get to see your prop is really crusty at low springs. Ho hum, guess it's the beach (or slipway) for me.:rolleyes:
 
Halo said:
Dear All
I serviced my 3YGM30 2 weeks ago - changed coolant, seawater pump impeller, oil, filters etc. Took her out for a motor in the flat calm last weekend. I ran her flat out for 5 minutes after warming up etc and the obverheat alarm came on. Idled her for a short time then switched off. Left her 10 minutes then motored in - all well. Plenty of raw water going through and no lack of coolant. any ideas about what could have caused this and what checks to make.
Thanks in advance
Martin
Click to expand...

Could have been an air lock that stopped the freshwater coolant circulating (since you'd drained the system).

It takes quite a while for the engine to warm up to a point where this would be a problem - I had something similar with our 2GM20 after changing the coolant - squishing the hoses on the fresh water system made it obvious that this was the cause and simultaneously cleared the air lock.

Just another 0.02p

Andy
 
Halo said:
Dear All
I serviced my 3YGM30 2 weeks ago - changed coolant, seawater pump impeller, oil, filters etc. Took her out for a motor in the flat calm last weekend. I ran her flat out for 5 minutes after warming up etc and the obverheat alarm came on. Idled her for a short time then switched off. Left her 10 minutes then motored in - all well. Plenty of raw water going through and no lack of coolant. any ideas about what could have caused this and what checks to make.
Thanks in advance
Martin
Click to expand...

As other have said about the first 5000 3YM30s made had an undersized heat exchanger: I had to chase Barrus/Yanmar to get this changed under warranty in 2006 - initially they claimed there was no problem. It was genuinely overheating then, measured by exhaust manifold temperature by an engineer.

Mine still can occasionally be pushed into overheat alarm with prolonged high throttle - which I make a point of giving from time to time to give the engine a bit of proper work. I think it is now more oversensitive alarm.

Barrus know exactly what serial numbers were fitted with the original smaller heat exchanger.....
 
You must log in or register to reply here.

Share this page

Top