Hi From Down Under

[Wotname]

Skipperpete is the real mechanic i.e trained professional etc; me, I am only an over enthusiastic shade tree DIY guy who has wasted way too much of life pulling apart and making old Yanmars work again.

OK, the grey sludge is not a good sign, that is salt water in the oil and that is never great. Of course, it isn't always terminal, far from it. Nevertheless it has to come out and it sounds like the engine won't be running for awhile yet. It has been many decades since I have been on a Roberts 25 so I don't recall how much access you have either side of the engine but with enough access on either side, it is possible to replace the piston and sleeve even with the engine in situ.

I would be inclined to remove head and have a look if you can't get the engine to rotate by hand. You could get a lot of the oil out by removing the crankcase cover on port side of the engine (opposite side to the head). BUT look carefully which way the cover is orientated because it is quite easy to put it back upside down with possibly disastrous results.

Hopefully Compass790 will chime in, he has much experience with this engine and can point you in the right direction for aftermarket parts.

[Gregted]

Originally Posted by Wotname

Skipperpete is the real mechanic i.e trained professional etc; me, I am only an over enthusiastic shade tree DIY guy who has wasted way too much of life pulling apart and making old Yanmars work again.

OK, the grey sludge is not a good sign, that is salt water in the oil and that is never great. Of course, it isn't always terminal, far from it. Nevertheless it has to come out and it sounds like the engine won't be running for awhile yet. It has been many decades since I have been on a Roberts 25 so I don't recall how much access you have either side of the engine but with enough access on either side, it is possible to replace the piston and sleeve even with the engine in situ.

I would be inclined to remove head and have a look if you can't get the engine to rotate by hand. You could get a lot of the oil out by removing the crankcase cover on port side of the engine (opposite side to the head). BUT look carefully which way the cover is orientated because it is quite easy to put it back upside down with possibly disastrous results.

Hopefully Compass790 will chime in, he has much experience with this engine and can point you in the right direction for aftermarket parts.

I think the head may have to come off but access is reasonable from the piston ( starboard ) side and the bow ( alternator ), side and also above for most of the alternator half of the engine.


I will also have look at the crankcase cover to remove the sludge as I don't feel comfortable starting it and distributing all that sludge throughout the engine if I don't have to.


There is an oil filter cover on the bow side which may give me access for a pump out. I'll have a closer look when I venture out in a week or so.

[Wotname]

Originally Posted by Gregted

...........
There is an oil filter cover on the bow side which may give me access for a pump out. I'll have a closer look when I venture out in a week or so.

Unfortunately you won't be able to suck any oil out at the oil filter point or at the oil pump point either.

[Wotname]

I would not stress too much about trying not to run the engine with the grey milkshake of emulsified of oil and water as it will already be circulated throughout the engine. Sure, do try to get it out as soon as practicable and flush new oil through the engine.

Without taking the front PTO case cover off which requires the removal of the PTO pulley nut, there are really only two options to get the old oil out.

1. Suck it out through the oil fill cap. See red arrow on picture
2. Use the drain plug (if fitted) underneath the crankcase cover. One photo shows the outer cover of the crankcase cover removed and the other shows the inner cover removed. Note the drain plug.

[MicHughV]

You may also have water in the cylinder, which will prevent you from turning the engine over as the piston will develop water lock.
The fact that there is water in the sump, means water in the cylinder is likely.

Water can entire the engine thru' the exhaust as well, besides other sources.

While it sounds terrible, I've resuscitated a diesel which had been complete inundated with salt water. Engine may smoke a little after.

At the end of the day, you might be best served by taking the whole thing apart.

[Gregted]

Thanks for the pics Wotname. I'll have a look for the drain plug.


Thanks for the reply MicHughV. I tried to turn over the engine with the injector out so even though there will probably be water in the combustion chamber, I don't think that was stopping it from running.


It's good to hear of that motor you resuscitated. Gives me hope..


I think just for my own peace of mind, I will at least take the head off and have a look. I have rebuilt many car engines in my time, so it doesn't seem that much of a job. One cylinder and no computer. Should be a breeze, right?

[Compass790]

Hi Gregted,
Damn I just lost a whole post so start agin.
My guess is you probably have a corroded exhaust elbow first most likely cause. I used to sell aftermarket parts for ys series yanmars & that was the most common cause of seizing the engine over time as seawater gets into combustion chamber thru ex v/v.
You could have blown headgasket too leaking water into oil galleries.
Less likely but still possible is cracked head.
You need to pull the head off as as bare minimum to inspect I suspect but agree with Wotname & MicHughv you are probably best served by pulling engine out to rebuild.
Not worth rebuilding if you buy genuine Yanmar parts & need a full rebuild as they are horrendously expensive but aftermarket is ok.
If you have rebuilt petrol engines you should be fine rebuilding the ysm12.
You might find this thread interesting https://www.cruisersforum.com/forums...-a-148914.html
Happy to answer questions

[Gregted]

Hey Compass790. Read that post and kudos for seeing the build through.

The exhaust elbow you speak of is the mixing elbow, I assume. Are you saying that they get blocked with corrosion and the gasses can't escape? My limited knowledge of the engine is that the mixing elbow just mixes exhaust gasses with the cooling water and discharges it through the exhaust.

Removing the engine will be a real bitch as the yacht has a dog box added to the stern of the cabin and the engine is built in under the sink. Almost midships..

If I take the head off and that doesn't solve our problems, I might remove as much as possible before we attempt an engine removal. I imagine they were made with heavy cast in the day.

It's currently moored in the local river but we can rent a mooring at the Gladstone Marina for about $200/week if needed. That would give us a stable platform and easier access to workshops.

[Wotname]

Originally Posted by Gregted

.........
The exhaust elbow you speak of is the mixing elbow, I assume. Are you saying that they get blocked with corrosion and the gasses can't escape? My limited knowledge of the engine is that the mixing elbow just mixes exhaust gasses with the cooling water and discharges it through the exhaust......

Here is a good primer about Yanmar mixing elbow problems. Every boating forum will have dozens of similar threads.
https://www.cruisersforum.com/forums...ow-103029.html

If I take the head off and that doesn't solve our problems, I might remove as much as possible before we attempt an engine removal. I imagine they were made with heavy cast in the day.

130kg.

[Gregted]

Hi Wotname.

I noticed that post was 10 years old but found this mixing elbow online and was wondering if this is the style I need.

Stainless is definitely the way to go and that part looks easy to build.

I assume the water just exits via the exhaust to facilitate easy egress of the cooling water so the pipe that attaches to the elbow just needs to enter at the join.

If that is the case, I wonder why the original part was so complicated and therefore prone to blockage. The original design should have had the water inlet more on the exit side of the elbow and therefore the inner tube would not be necessary.

Having the water inlet on the engine side of the elbow and then having to travel over the elbow to the exhaust side makes no sense at all.

The stainless one would work better if the water inlet was angled towards the outlet and I guess could even follow along inside the pipe towards the outlet for a time.

Also just found this add for a new elbow for $275.22 delivered, so not bad for a factory but may be able to build one for a lot cheaper out of stainless.

[sailorladd]

I am getting a sense of Deja vu , as I had an old YSM 12 in my 32 footer and it was the most reliable old diesel I could have ever put in my boat.
I loved it dearly and it served me faithfully for all the years of cruising from South Africa across to South America, the Caribbean, the Pacific etc ... I had many adventures with her and I talk about them in a book I wrote after I was done cruising.
I would heartily endorse her and hope that it is an easy fix... definitely worth the effort...BTW, I spent a year in Bundaberg up the Burnett river...It was a wonderful experience and I met so many wonderful kind people...

[Shaneesprit]

If I were you.
I would remove the engine and find a non marine workshop to repair it. - as you have an outboard it will be the simplest and possibly the cheaper option.
Small Garden / farm machinery type workshop.

[jakkum]

OTE=Gregted;3855115]I think the head may have to come off but access is reasonable from the piston ( starboard ) side and the bow ( alternator ), side and also above for most of the alternator half of the engine.
If Derry
IF THERE IS SLUDGE THE ENGINE HAS RUN BECAUSE THE ENGINE MAKES THE SLUDGE
I HAVE SEEN MANY ENGINES WITH SLUDGE INSIDE BUT THAT DIDN'T KILL THE ENGINE IF IT RUN FOR A SHORT TIME
YES FIRST TRY TO GET THE ENGINE LOSE THAT YOU CAN TURN IT OVER AND THEN PERHAPS YOU CAN START IT IF THE FUEL SYSTEM IS STIL OKÉ
THEN YOU KNOW SOMETHING AND YOU CAN START ON GETTING THE RUBBISH OUT
WE HAD ENGINES SITTING IN FULLT WATER OM DE BOTTOM OF THE SEA IN DE SHIP EN AFTER WATCH TIME WE JUST GOT IT RUNNING

ALL OIL HAS TO BE CHANGED AT LEAST TWO TIMES

I will also have look at the crankcase cover to remove the sludge as I don't feel comfortable starting it and distributing all that sludge throughout the engine if I don't have to.


There is an oil filter cover on the bow side which may give me access for a pump out. I'll have a closer look when I venture out in a week or so.[/QUOTE]

[nofacey]

Too many identified items (sludge, disconnected water, not turning over even manually) that I’d stop trying to “start” the engine and just tear it down - small enough you can likely do this in place.

[Compass790]

Well if its that much of a problem to remove you may be able to do it in place. Its certainly may be possible but a lot more difficult to work on in the boat.
If you look at the mixing elbow in the pics of the link that Wottie supplied you will see the water inlet is on the side of the pipe that comes out of the head i.e. the exhaust gas is rising. What happens if it corrodes through near where the water inlet comes in the water can go down onto the inlet valve. It might be ok when combustion is happening as it gets blown out I'm guessing but as soon as combustion stops the water will go into the combustion chamber whenver the exhaust valve is open.
I shall try & find a link to the exhaust elbow I made that makes it impossible for that to happen. Its much cheaper to knock one up out of sched 10 ss pipe & elbows if you can weld or have a cobber that can,

I suspect your bore will be rusted as suggested in earlier posts.
You will probably need new rings, liner, exhaust valve & head gasket but see when you get head off. They can run with water damaged bores, it all depends on compression. I dont have the figure for 12hp as its lower compression than the 8hp. But the 8hp is about 435 psi

In my experience you are much better off with a diesel inboard than an outboard if you sail in rough conditions so worth fixing if you can. Plus electrical generation from an inboard is nice.
We used an outboard whilst I worked on the inboard. I lifted the ysm 8 out by myself with everything off it but 12hp is heavier but 2 blokes should be able to do it.
Of course your first mission is to unseize it but if you cant do that you will have to pull the liner. ATF & acetone mix 50/50 in inlet if valve is open or in injector might help