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Old 08-03-2014, 20:42   #1
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1GM Yanmar Cooling water blockage: Lessons learned

I usually end up regretting starting a thread which seeks to inform, rather than asking a question. I should really put this on my blog, except I don't have one.

Here goes anyway. I think some of the lessons have wider relevance than the context might initially make it seem likely.

The other night I went for a night-and-day sail with a friend who a few decades ago built the nicest 23' offshore cruiser it has ever been my pleasure to crew on, and sometimes borrow for my own use
(Undying thanks, Mate!)

This is a boat which can be (and generally is) stored ashore, and trailered to the sea, because the steel keel can be retracted.

Due to storms [which incidentally broke the heavily regulated and regularly inspected and maintained moorings of more than half the boats in a nearby harbour of refuge and drove them onto the rocky foreshore],all the usual launching ramps are currently damaged and unavailable.

So we canvassed the alternatives, eventually finding a (marginally) usable ramp about an hour's drive from town.

The surface of the sea was still thickly carpeted with trash, a mixture of broken-free seeweed and seagrass, shattered timber shards and twigs from trees destroyed in the storm, and general accumulated flotsam and jetsam, refloated after the storm surge took the tideline to the highest level in years.

We were not too concerned about the implications for cooling water, because this boat has a Yanmar with a saildrive, where the inlet slots on the drive leg are on the midline of the boat, below the hull and well below the carpet on the surface.

We were more concerned about the effect on traction for the towing vehicle from the masses of trash on the ramp, redeposited with every surge (the ramp being quite exposed to a long, low ground swell, curling into the bay.

This turned out not to be a problem, despite being a modern 4WD relying on electronic smartypants traction control rather than locking diffs)

So my mate drove the truck and I the boat, and everything went smoothly as we launched just on dark.

Until (having already motored gently back off the trailer) I went to back off in earnest, and it was clear the (standard 2 blade folding) prop was fouled. I gingerly eased it from forward to reverse a number of times, which normally does the trick, but no improvement was forthcoming, and clearly one blade was not deployed.

A third member of the party was luckily aboard and luckily a good seaman, and he had meanwhile snared a pile with the bowrope, so I though I had better "take one for the boys" and be the one to strip off and lower myself into the sludgy muddy soup, fight through the thick carpet of organic matter, and (as it turned out) get a bit disoriented and head butt the trailing portion of the keel.
But I could tell by feeling it where I was, and that sent me in the right direction to find and clear the problem without having to go back for more breath.
First learning follows (actually I 'knew' this one, but had forgotten, and luckily it is easily fixed without needing to start again)

I'll put each point in a separate post, to make discussion easier
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Old 08-03-2014, 20:43   #2
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

(1) By all means do a bit of hyperventilating before going under a boat with no suit or weights, but DON'T fill your lungs full, or you will be pressed too hard against the underside of the hull to be able to travel efficiently about.
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Old 08-03-2014, 20:47   #3
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

There were fronds of wide kelp and sea-lettuce wrapped around the prop, but because I had alternated from ahead to astern without doing any long bursts, it was easy enough to brush and flick it off with one hand, and open and close the prop to check for binding. I then felt the slots of the cooling intake and they felt clear.
So I returned to the cockpit and dripped dry while we had another go at heading off to the jetty where my Mate was going to join us, not having thought to pack a towel.
I had got within 200m of the jetty when the temperature alarm went off. I took the chance and pointed upwind and up-current of where we needed to end up, gave the motor a burst, then turned off when I judged we would coast the distance. Naturally I erred on the side of not falling short, so there was a solid "THUMP" to announce our arrival, in spite of everyone's best efforts (do not try this on a bigger boat!) but no damage done.

First job was to check that cooling water was emerging from the transom. Check: it wasn't.

So yours truly, being still the naked shivering member of the party, slipped over the side with a degree of resignation (there being no carpet out here) and checked to see if we'd picked up another blockage inshore where it was rife.
No obstruction.

We had a good enough wind angle to sail through the adjacent moored boats and anchor, thinking we had enough tools on board to fix the problem. Yanmars are generally quite good to work on, and none of us had struck a situation to do with engine temperature on a Yanmar that was beyond being fixed afloat.
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Old 08-03-2014, 20:49   #4
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

2) We should have pulled off the hose to see if the water was getting this far before I went back over the side: no harm done, except that now I am fighting off a cold which I'm sure I would not otherwise have incurred. We could have done this step sooner than we did, and I could have got dressed and rewarmed once that problem was ruled out.
The boat is only as happy and secure as the crew so there's no point in being a hero.
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Old 08-03-2014, 20:54   #5
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

So the next likely problem (probably the first one most people would check) was for the usual Yanmar impeller debonding, where the central bush with the D hole keeps spinning but the spiral arms of the impeller remain resolutely immobile.
It would be a work of moments to flick the impeller cover off, we thought. We thought wrong. Somehow, the crankshaft pulley had managed to block off the access to one of the fasteners. The screw in question was a Phillips head, and although we had a ratchet driver on board, it required too much headroom to get it onto the screw.
We don't know how this came about: I can only presume that the last time the impeller was changed, my Mate had the crankshaft pulley off, and mistakenly used the wrong screws. Otherwise we would surely have encountered this problem.

Which was somewhat difficult because, being a small boat, we had no large enough sockets for that particular nut, and even if we had, no strongbar long or strong enough to turn it.
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Old 08-03-2014, 20:55   #6
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

4) IF you have an integrated, direct-drive salt water pump on your engine, if you haven't fitted a crafty aftermarket kit with a new, thicker, slotted impeller cover plate with thumbscrews and an O-ring seal, and unless you're CERTAIN you have the right tools to get at the fasteners:


It might be an idea to do a 'dry run' and make sure you can access the fasteners with the tools you have.

In the case of the culprit engine under discussion (hanging its head gasket in shame), the fasteners will be swapped for Hex head screws, which my own 1GM (see photo) has ex factory. The problem immediately goes away.
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Old 08-03-2014, 21:28   #7
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Re: 1GM Yanmar Cooling water blockage: Lessons learned



Point of Clarification re model of engine:

BOTH my Mate's engine and my engine in the photos are 1GM10 salt water cooled Yanmars. His is one of the first of the 1GM10 as opposed to 1GM motors, and I'm not sure what changes there were in this area.

I'm sorry about the title being a bit misleading.
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Old 08-03-2014, 21:47   #8
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

Lots more to come; there were several more lessons learned, some about boathandling and some about troubleshooting.
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Old 08-03-2014, 23:11   #9
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

So the next phase was to have a wee think about how to get at the impeller without the necessary and very unusual tool to do so, given our unquestioned inability to remove the crankshaft pulley.

(As the photo shows, the invisible screw pointed at by Arrow "B") has remarkably difficult access, given that unlike my one in the photo, the 1GM10 on this boat had Philips-head screws.

I'm sure someone in the audience is shouting out the answer, but I'm not sure how long it would have taken me to twig, because my Mate thought for a half minute and then said: "I bet if we take out the other two screws, we'll be able to tap the cover around anticlockwise, and the mystery screw will loosen."

After we'd had a quick squizz with a torch to establish there was no impediment to the cover doing that, and thumped him on the back, we did exactly that. We had to use a flat stainless plate with square cut ends (a nice, simple homebuilt deck-fill spanner) along the long straight bottom edge of the cover as a drift, and the heavy cast starter handle as a club hammer, but that did the trick nicely.

I guess there might be someone reading this who is puzzled how this could work, so I need to explain for the benefit of anyone who's never seen inside an impeller pump that the cover plate is flat inside (at least, when new!) and does not in any event protrude into the body of the pump.

5) Sometimes the last screw in a cover plate of flange can be loosened even if inaccessible or jammed, by knocking the whole flange around.
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Old 08-03-2014, 23:38   #10
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

To our surprise and disappointment (it was ~ 2300 and our stomachs were starting to rumble) the impeller was in excellent order. (We had a spare)

6) Sometimes the obvious answer (Yanmars are NOTORIOUS impeller consumers) is not the right answer. And it was partly in recognition of this that we did not make a beeline for checking it.

In the case of a linear, sequential system like a cooling circuit, I reckon it's safer to trace from the entry end to the exit end, rather than taking guesses and jumping around.
Firstly because the information you gather upstream may alert you to what things to look for downstream, and perhaps more importantly, because methodical linear problemsolving makes it less likely you'll miss one of the possible culprits.

I've already mentioned an exception to this my no means rigid rule: It would have made more sense to verify that the problem was upstream of the hose at the inlet of the impeller pump, rather than me diving over the side, unnecessarily, a second time.
Another obvious exception is when time is a matter of consequence rather than (as in our case) convenience.
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Old 08-03-2014, 23:58   #11
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

And here we broke 'rule' six, just given, and for no very good reason (but having said that, with no great penalty).

The next obvious culprit was the thermostat. This is at the far end of two paths: one at the exit point of the salt water having flowed through the engine, which entered it at point E.

The other is the far end of the hose carrying salt water from the top branch of the Tee in the above picture, namely outlet F. This flow is effectively direct from the pump, having flowed through hose CD.

I'm always a bit sketchy about small marine diesel thermostats: I know there's some counterintuitive things about them but I tend to forget what they are.

My mate has a phenomenal ability to work things out from first principles, so while I got stuck into taking off the cover and blocking it off with the coverplate from the impeller hosing so I could blow down the side inlet, he was puzzling over the problem.

So by the time I had announced that I could blow easily backwards down the hose (removed in the picture) from outlet F to the outside inlet port of the thermostat cover, but that I could NOT blow through the engine, (despite disconnecting hose CD) he was ready to explain what we were dealing with.

His explanation was not actually crucial to solving our problem, but it was interesting and would have greatly helped me on past occasions, being a diehard diesel dunce: I thought if I carved it in internet tablets here and now, at least it might be of use to one person at a future date. (namely, me)
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Old 09-03-2014, 00:08   #12
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

7) The thermostat is NOT simply an on-off device, shutting off a flow path. It looks like one, so this is counterintuitive.

It is a diverter of flow, from path 1 to path 2. Like a Y-valve.

When the engine is cold, the thermostat valve blocks the saltwater coming OUT of the engine (second counterintuitive point), and permits saltwater from the pump, which has arrived through the hose from F to the thermostat cover, to flow to the outlet port from the same cover.
From there it travels to the exhaust elbow, where it cools the exhaust, although it has NOT passed through the engine.

The exhaust ALWAYS needs cooling, because the exhaust gases heat up much earlier than the engine block with 'all' its thermal mass, even in the case of a puny 1GM10.

(This seems to me to help explain why exhaust elbows are so prone to rotting through at the injection point, 1GM10 engines being a case in point, but the explanation will have to wait)

When the engine gets hot, the pressurised but stagnant water in the block conveys that heat to the thermostat by conduction and convection, since the 'stat is at the top of the engine, and the wax expands in the bellows and pushes the disk across, which BLOCKS the bypass flow from the hose, from F, and OPENS the main flow, from the engine (coming from the far end of the cavity into which the bellows of the 'stat are buried), out the outlet port in the 'stat cover, thence to the exhaust elbow injection point as before.

Phew. Any corrections or clarifications or exceptions or omissions gratefully received.
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Old 09-03-2014, 00:13   #13
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

typo:

5) Sometimes the last screw in a cover plate OR flange can be loosened even if inaccessible or jammed, by knocking the whole flange around.
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Old 09-03-2014, 00:29   #14
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

With the thermastat housing off It would be worthwhile to insert a thin long bladed screwdriver into the block. I found a blockage in that area. Have found it easier to pull off the pump rather than mess with it on the engine. Carry one spare pump.
ps had one overheat & when the inlet hose was pulled off a little fish dropped in.

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Old 09-03-2014, 00:31   #15
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Re: 1GM Yanmar Cooling water blockage: Lessons learned

OK, we're getting to the interesting part folks, hang in there.

SO now we know the blockage is somewhere between point E (the branch of the tee screwed in to the engine, where the salt water enters the block) and the thermostat cavity in the block. It has to be either somewhere in the engine, or somewhere in the T.

Everything says the next thing to check is the T. Specifically, the "run" of the tee, from D to E; we already know the "branch" of the tee, at F, is clear through to D.

So my Mate grabs a scriber from the toolkit and pokes the run of the T "up the gunga" . And encounters resistance within a short distance. He wiggles, and a drop of moisture appears. He wiggles more, and it becomes a trickle. In less time than it's taking to write it's a healthy flow, while the block empties. The blockage was a mixture of wood fibers and seeweed pulp, which had made it through the pump without damaging it visibly, but there must have been a ring of crystallised salt bound up with corrosion product constricting the tapped port in the wall of the block that the T screwed into, making it temporarily smaller than the bore of the T , so that's where the trash became first a filter screen to catch further trash, and then in short order a perfectly sealing plug.
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