3GM30 overheating

[Sos]

Hi,

We have a Yanmar 3GM30, raw water cooled, that has started overheating.

I have changed the impellor and the thermostat.

Also flushed it through a couple of years ago with Ridlyme.

Still get a good flow from the exhaust outlet.

Ran for about 10 minutes before alarm went off. Temperture at the exhaust elbow was 62 C. Our other 3GM30F (fresh water cooled) runs at about 35 C.

Any ideas?

Chears, Steve

[barnab]

Did you measure flow at the exhaust? As you have two engine, I would measure (bucket and stopwatch) - it's really hard to estimate water flow by just looking at it.


Mixing elbow is a suspect, did you check the raw water intake for blockage?

[Sos]

Only looked at the flow which looked similar.


I did recently replace the mixing elbow on the other engine and it was pretty carboned up so could well be the same on this engine.


I have looked at taking it off but some of the fixing bolt heads are partly rusted away so didn't get any further! Was going to leave until the off season but may have to move that forward.


Intake is on the saildrive so not sure.

[barnab]

The pickup tube in the saildrive makes a nice home for all sorts of creatures...You could try to pick up the water instead of through the through hull from a bucket to see if there is a restriction in the saildrive (always measure with a bucket to compare).