Yanmar 3GM30F exhaust manifold/heat exchanger question

[Chris & Lenore]

My "new to me" 3GM30F has about 350 hrs on it, over a period of 14 years.

This winter I plan to check the exhaust elbow plus remove and inspect/clean the heat exchanger core (has never been serviced).

From looking at the shop manual and the tight engine room (V drive) it looks far easier to just remove the entire manifold and work on it at home over the winter.

My question - is it just the hoses and 6 bolts holding it on? Do the bolts come out easily? I have had nasty experiences with car exhaust manifold bolts.

Hopefully it's as easy as it looks?

Thanks,

Chris

 

[Steve Dion]

Chris:

I think that it is only 4 bolts that hold the manifold in place.

One part of removing the manifold that is not easy is removing the exhaust hose. We used a screw drive to push between the hose and the elbow. Then I sprayed some WD-40 in the crack. I would get the hose off before you attempt to remove the manifold.

You may find that your elbow is still intact. When they operate in fresh water there is very little if any coking. If that is the case I would just order a gasket and put the unit back on.

You should also get some never-sieze (sp?) to coat the threads. If you elbow is coked you may want to get a new coupling too (left/right threads).

 

[kloudie1]

Chris, yep.. the 6 nuts on studs on each side of the head exhaust ports.. because they are water cooled, they will be a lot easier than the same ones on a car.. Some 3GM's have the secondary fuel filter hanging on two bolts from the bottom of the manifold.. yours may or may not.. other than that, the two coolant hoses, the two sea water hoses, and the exhaust hose and the whole thing is off.

 

[Chris & Lenore]

Excellent news! Thanks for the replies. I'll remove the exhaust hose while the manifold is attached to the engine - that makes perfect sense.

Hopefully the heat exchanger will be in good condition (only seen fresh water). My concern is more on the engine side - I don't think the coolant has been changed for several years.

That leads to another question - I see lots of recommendations as to when the seawater impeller should be changed but none concerning the freshwater pump/impeller. I assume that since they run in an anti-freeze solution the bearings fail before the impeller?

Thanks,

Chris

 

[Calif. Ted]

The freshwater pump is on the front of the block and uses a metal impellor, it's like the water pump on a car.

 

[Chris & Lenore]

That makes sense. I only had a diagram in the shop manual to go by - it looked similar to the raw water impeller.

Thanks,

Chris