1GM Yanmar Cooling water blockage: Lessons learned

[Andrew Troup]

Even well designed, salt water cooled marine diesels are prone to the cooling passages in the block clogging. This boat lives ashore except when on cruising duty, and is flushed whenever pulled from the water.

However this was actually a good thing in this instance, because the crap was kept from finding its way right through the block.\

That's a strange scenario though, and there are better ways of straining the seawater, which I will discuss. So anyone with a small marine diesel would be well advised to quite frequently give the passages a good talking to

I'm going to do this so I'll try to remember to post some of the methods which trial and research suggest might be worth passing on, if any

I'm thinking suitable scraper buttons (bevelled discs, like a conical carbide turning tip, perhaps, ground thinner) screwed to the end of a mild steel handle which can be bent to get partway around some of the bends. I don't know if it's possible to poke a chain through any of the paths, and use it like dental floss....

The engine's life will undoubtedly be affected once the buildup reaches a degree where some passages no longer have a viable flow path.

[Andrew Troup]

@ bill good.

Thanks for those ideas. The one about clearing the passage to the thermostat is a great hint, for one. (Ours was in good shape)

We seriously considered the idea of removing the whole pump, but as my Mate pointed out, in the case of the 1GM10, the pump is actually direct driven from an internal gearset and its housing is sunk into the front of the block below the oil level. (I've just gone out and verified by taking the pump housing off my engine, whose oil is currently drained, and there's a coating of oil on the internal parts of the coupling which comes off with the pump - Thanks for reminding my because I meant to check that on my return, but had forgotten ! I'll let my mate know he was right)

So taking the whole pump off for us would have involved removing all the belts, draining the engine oil, and in our case, to get at one of the hex bolts holding the pump housing to the block meant using a cranked ring spanner deeper than the one we had.

On my 2GM20F where the parts are otherwise largely interchangeable in most respects, the pump is a stand-alone item, easy to replace, and your suggestion would work well, so maybe you have a 2GM or a 3GM?

[Andrew Troup]

@ bill good again:

Regarding catching dinner in your saltwater intake: although I know people who've done this, it has only happened to me once, and it was an eel.

(NOTE: the word "YOU" in the following is not aimed specifically at you, Bill, but at anyone reading this, which helps me realise that may well also applies to your post, and its applicability to the usual situation, where the saltwater pump is stand-alone)

Although it was evidently a large-ish eel (the inlet was quite sizeable) I'm guessing it was stressseed out and somewhat stretched and lengthened by circumstance and suction alike on insertion, because it showed all the signs of being a large (and long, and VERY tough) plug in a smaller diameter hole. Not good news.

I like standpipes (mainly used on metal hulls, but can be applied more widely under certain controlled circumstances) because what happened to that eel was that the bit outside the boat, and the bit in the flexible hose, both became sustantially larger than the bit in the non-expanding metal ball valve and thru-hull. This caused it to develop a wasp waist (although of course much more subtle) and meant that trying to use air to force it out would have just enlarged the eel, which had gone in head first as you would expect, and things would no doubt have gone quickly downhill from there. Bear in mind that one did not at the time KNOW it was an eel.

Ideally a standpipe would be a conical bore, reducing gently all the way up to the waterline .... but that would use a great deal of material to do from solid, and I don't fancy welding it.

In the case in point, we had some joiners, but no long lengths of suitable hose spare, but IIRC we were able to leave the eel as a guardian of our watertight integrity (he was certainly a hell of a lot more "integrated" than the mandated 'soft wood plug') , cut the hose off inboard of his head, and splice the remainder to a less essential hose leading to another thru-hull which was re-purposed.

INCIDENTALLY: on the "softwood plug" topic: I didn't realise until the occasion arose that there is actually a good feature in the fact that the taper is always too bloody steep. I always realised it was to extend their diametral range, but it bothered me that as a result they did not stay in place.

The "good feature" I mentioned is this: Provided you have spares of each size, (which you should do, as usually many thruhulls on a given boat will be the same diameter) a good way to go about things is to use the first for two purposes: Ram it in the offending hole, and get someone to lean on it. Take an OTHER identical plug, and mark on it the amount protruding from the first one, which is being used for immediate relief but also as a tapered gauge: a primitive but effective way of measuring holes.

So now you whittle away the second plug, starting a little way towards the smaller end from that point and working towards the BIG end, so you end up with a much shallower taper starting at a diameter which, as well as you can judge, will go about an inch into the fitting.

And the softness of the wood should do the rest.

Don't smack it in too hard, especially if you made a really shallow taper, or you will risk splitting the fitting, especially when it swells and is unable to back out.
If you have a Zyliss vice (I forget the model) and a galley bench to clamp it to, you can use your electric drill motor as a lathe headstock in the supplied clamp, and use the Zyliss tailstock, and make a superb job of it ! But whittling (or, quicker, a decent wood rasp) will do just fine.

[Andrew Troup]

I had another post written on the denouement of the saga, but the forum software sneezed and my post is now adorning a virtual kleenex in the cyber recycling bin ...

Haven't quite got the impetus (given my state of health - sniff) to make it back up the cylinder towards the ignition stroke, so that'll have to wait till tomorrow, folks.

[Badsanta]

Thanks for taking the time to explain this.

[dbraymer]

Cat 30s have a worse diversion thermostat thingee on I believe a universal 2504???
Drive you batty. everything in the cooling circuit is fine, but no water comes out the pipe until the diversion is removed by the thermostat. I guess no old bad idea can be left alone for long by a new engineer

[Andrew Troup]

@dbraymer

That's intriguing. I did know that running some Caterpillar diesels with the thermostat removed actually caused them to overheat, rather than (as usual) to take an excessive time to reach running temperature, or run cool !

Before I pick up this thread, I'm just wanting to do a bit more research to find out EXACTLY how the thermostat on the 1GM10 (and 2GM20F) works, so that I don't mislead anyone.

[Andrew Troup]

OK; I've done a bit of delving into the literature, and searching past discussions on this and other internet groups, and there's remarkably little about marine diesel thermostat circuits and the different options.

So .... I figured it deserved a thread of its own, which I have started. Marine Diesel Thermostats: NOT WHAT THEY SEEM - Cruisers & Sailing Forums


As for the blockage which got me pondering these matters in the first place:

Here's the final wrap-up, including my best guess at what went wrong, and some thoughts about what I'd do if faced with this situation again.

The reason for the blockage was essentially that, on entering the water, the saildrive passed through the carpet of trash for a significant period (on a shallow angle), something which would never happen under normal circumstances.

In doing so, the unfolded prop would have picked up a whole bundle of seaweed mixed with wood trash

- - - - - - - - - - - - -

Main learnings:

DO NOT use the ahead/astern trick when the prop gets fouled, for saildrives without strainers, unless you are confident the cooling system will pass the resulting debris without retaining any.

When launching any boat with a saildrive with no strainer (even a keelboat on a cradle) through a carpet of trash on the water, don't have the engine running unless you can arrange a temporary alternative source of cooling water.*

(Note: We didn't have the engine running until the boat was on her lines, which SHOULD have kept us safe – but we still needed some way to clear the above-mentioned "bundle" off the saildrive.

I guess we could have turned the motor by hand, slowly, in forward, a few turns with the decompressor open, selected reverse and done the same, and cleared the prop that way, before starting the engine.

Cranking it electrically would have sucked up the trash, and once in the sternleg, it would have inexorably found its way into the engine.)

*I'm increasingly inclined to think that some prearranged ad hoc daytank would be a good thing to have, perhaps using either the galley sink, or the cockpit well (if it has a compact low region or a sump).

For seawater cooled engines which are rarely used, this would also provide a handy way of flushing the system with freshwater.