Yanmar 3GM30 direct cooling: good option?

[wimd]

Fell in love with an Elan 36 but before buying it, I would like some more info regarding the 27Hp Yanmar 3GM30. This model is direct cooled with sea water. What are the disadvantages of this type?
Durability of engine? -> clogged hoses?
Do you need seawater inside your engine? better go for indirect cooling version and let the love of my life dissapear on the horizon?
Any tips more than welcome!

 

[rob2]

I think you've covered the main disadvantages, although boat engines with direct cooling have been successfully used for decades. Part of the problem is that to limit crystallisation of deposits in the engine, the engine is run cooler than its indirect cooled version which slightly reduces the engines efficiency and therefore fuel conmsumption. Its not likely to be hoses that clog so much as the smaller channels within the block and cylinder head, but I seem to recall that the 3GM30 has pressed-in cylinders with large cooling volume around them, so the cylinder head is more likely to suffer.

Before rejecting the boat, you should consider how long you would hope the current engine will last and its replacement cost and compare with how it compares with the situation should you find one with an indirect cooled version. Shold the engine be approaching its life expectancy, then it makes little difference although you might be able to justify a lower bid price on this basis.

Rob.

 

[prv]

Never had any bother with my 2GM20 (very similar engine with one less cylinder) in Kindred Spirit. I can see that raw-water cooling may not be a very good idea with marinised van engines, but I believe the Yanmar GMs are purpose-built marine engines with good spacious waterways.

Keeps things nice and simple.

Pete

 

[wimd]

So what to do after a nice day of sailing? You just did a perfect manoeuver under engine to arrive in your box and are ready for the first cold beer. Is there any need for flushing with fresh water like it is common sense with outboard engines?
Any ideas how to check the amount of crystallisation, eg how to know if engine is approaching his (or is it her?) life expectancy?
Thanks anyway for the replies!

 

[prv]

So what to do after a nice day of sailing? You just did a perfect manoeuver under engine to arrive in your box and are ready for the first cold beer. Is there any need for flushing with fresh water like it is common sense with outboard engines?

No!

Switch off the engine and open a beer. Job done.

There are a pair of anodes inside the engine block which need to be inspected annually and changed if necessary - not difficult at all once you've found where they unscrew from. I recommend a good coating of grease on the threads when you screw them back in, then they'll come out even easier next time. There shouldn't be any significant build up inside the waterways, though a decent strainer to ensure you're not pumping sand and weed through the engine is a good idea.

Pete

 

[rob2]

I believe the 3GN30 has three anodes, one in the CH and two in the block.

Rob.

 

[Fr J Hackett]

If you are that bothered Yanmar do a conversion kit to change to indirect cooling it's expensive though!

 

[Jabamusic]

I believe the 3GN30 has three anodes, one in the CH and two in the block.

Rob.

Three I believe - as rob2 states

Great engine, and certainly no need to flush out with fresh after using it.

The maintenance manuals are freely available and well worth getting hold of.