Yanmar 1GM10 Head gasket

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Dom315

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I am considering buying a boat with a 1 GM10 engine which is 6 years old and said to have had little use.
There is corrosion around the joint between the head and the block. This is a like a sort of white powder and I guess caused by the egress of salt water from the cylinder head.
The engine has not been winterised and so the presence of raw salt water in the engine over the winter may have enabled this to occur.
The exhaust elbow shows evidence of corrosion to the internal weld and to the surrounding surface. I am told the elbow will need replacing.
To ensure that the head gasket is serviceable the engine would need to be run under load for a period of time to ascertain whether it overheats. This can obviously not be achieved out of the water.
I guess that an engineer would recommend that the head be removed and the head gasket inspected and changed. This would be the only full proof way of establishing the cylinder head/ engine block integrity. This will obviously involve costs which I think should be reflected in the price of the boat.

The thermostat was changed prior to bringing her out of the water last September. If she had been overheating prior to this, it could also be an indication that the problem could be the head gasket.
These are my views following talks with an engineer. Does anybody out there have views that would support or contradict this. I would be concerned at buying trouble which may not manifest itself until I need the engine most.
 
I suspect that the head gasket hasn't gone at all as this sort of powdery trace often occurs for some reason around head/block joints, possibly due to interaction between head metals and whatever is in the exposed edge of the gasket.

I'd do a deal based on changing the gasket for sure, but run it afloat before you actually change the gasket as you'll probably find it runs just fine. Also, corrosion around an exhaust elbow #weld is not unusual, heat plus metal plus seawater = rust acceleration! Elbows can be diy fabricated

ExhaustElbow.jpg
 
Thanks and that's useful to know. I expect that I would run it for a time to see how it stood up but as you can imagine when in the buying seat, I need some views as to others' experiences of this engine.
 
My own researches suggest that this is fairly unlikely to be the head gasket failed. Check the colour and consistency of the oil as another possible clue.

Another common problem is a leaking water pump; salty deposits down the front of the engine are an indication. If yours has this also check the condition of the external oil pipes which can suffer corrosion as a consequence. Pump overhaul is fairly simple, about £30 for parts and a reasonable DIY job.
 
To add to the suggestions of the others, just make sure the compression is good, if it is i would leave the head alone. To tset if the compression is ok turn the engine over by hand upto compression, it should be very difficult to move past this point. use starting handle if available or socket on tommy bar or ratchet.



Steve
 
Very helpful suggestions from all and yes the compression is good and the oil clear. This would tend to confirm respondents views. I guess I'll proceed along the lines suggested, re negotiate and replace exhaust elbow and wait and see. If you see lots of white smoke coming from a little boat in the Solent in the next few weeks, I hope it will be someone else!
 
The exhaust elbows are a common failure item and the chief problem is Internal corrosion. This allows salt water into the exhaust manifold which leads to all sorts of nastiness. If it were mine, I'd replace the elbow before running the engine. If the existing elbow is OK inside, I'd dowse it in rust killer, spray it with waxoil inside and out, then wrap it up and keep it as an emergency spare.

With regard to the DIY fabrication sketch, the injection pipe should pass through the hole and be bent towards the exit to prevent the above threat of water ingress.
 
My hasty artistic licence. Actually, engineering-wise, the only time water flows is when the engine is running and exhaust pressure shoves it down the exhaust hose pretty smartly. Nevertheless, yes, you are correct in that the injection spigot should if possible be angled in direction of gas flow but it has no effect on performance if it does not as it is located on the downwards pointing part of the elbow,
 
I had a yanmar YSB8 that also used to have white powdery deposit between head and block faces. Never knew what caused it but it wasn't the head gasket..
Comes off very easy with an old toothbrush. Maybe something to do with the engine anode needing replaced /forums/images/graemlins/confused.gif.
 
Unlikely to be any problem with the gasket. The engine as yoiu know is seawater cooled and mine after over 20 years has always had that salt rim.

Suggest you do the following. Remove and replace the exhaust elbow with a genuine Yanmar one. Early corrosion is usually down to short running periods and lack of anti syphon. Make sure it has an anti syphon and ideally a properly installed Vetus water trap. Again, my engine is still on its original elbow.

Take off all the water hoses and clean them through. The often fill with deposits, again worse with low usage. Pay particular attention to the short vertical by pass hose at the front. Take out and clean the fitting that takes the water into the block. Replace the anode (cunningly hidden behind the starter) and check there are no heavy deposits in block water jacket.

Make sure the water pump is not leaking as this can corrode the external oil pipe below it and then the alloy housing. Fit a new impeller and invest in a Speedseal cover - removing the normal cover will convince you of the need for this.

My boat is in the water all year round I run it regularly under load and have never "winterised" it, just regularly checked as above.
 
Fantastic information that gives me a positive feel for going forward. Back to negotiations now. Please excuse typos as on Blackberry
 
No more expensive than other elbows on say Volvos or Bukh. In my experience it lasts well. My engine is 22 years old and still has its original elbow.
 
They are ALL expensive to buy which is why, as they are so easy to make, I suggested a diy one. It is one of the few engine parts you CAN make yourself and save a bomb plus have the satisfaction on having done it. However, do use cut pipe and NOT malleable elbows or other "fittings" as they are not ideal for welding.
 
The only problem with your design is that it does not have the inner tube of the original. The water is injected against this tube which carries the exhaust gases. Others have replicated this design in SS, but it is only economical if you have the equipment and skills to DIY. I would be reluctant to use a simple one like yours in an engine that is known to have problems in this area.

BTW the service manual warns of the potential issue here and suggests regular checking and cleaning which is an easy job.
 
You can start it on the hard.

If it starts in the 1st 2 seconds then don't bother to change anything. If it's been standing around for some time then prime the injector by turning the crank with the decompression lever up and listeming for the familiar bzzppp at the injector. If it starts in the 1st 2 seconds then all is OK ...

HOWEVER: Check the existing exhaust elbow for soot build up. Exhaust elbows should be changed either approx every 5 years or every 500+ hours use .... water back flooding into the cylinder causes conrod compression, loss of compression and a whole series of very expensive bills.

If you are really really really concerned about the condition of the head gasket and the engine doesn't start 1st time even on the hard (don't worry about there being no water in the system as you are only going to run it for say less than 2 minutes) then do the solder wire test: Remove the injector; remove the top half of the swirl chamber and poke about an inch of 2mm solder through the middle of the 3 holes in the bottom half of the swirl chamber keeping the solder wire exactly in line with the cylinder diameter according to the direction of the centre hole . Turn the engine over several times by hand. Withdraw the solder wire and measure the thickness of the squashed solder wire with a micrometer. It should be betwee 0.68 to 0.88mm ie 0.68mm = ~460 lb/sq inch pressure (23 : 1)

Yanmar GM series engines are prone to early failure due to backflooding caused by overcranking = a buildup of water not being exploded out of the exhaust system caused by bad 3rd party exhaust design. IMO, you should work out what size water seperator is needed for say a maximum 20 second crank - an oversize water seperator is at least 1000 times cheaper than an engine rebuild!.

I'm now onto my 3rd engine rebuild all caused by a defective exhaust installation - It's sofar cost me more than the cost of a new Beta + exhaust system to maintain my most hated friend, my Yanmar 1GM10 /forums/images/graemlins/frown.gif /forums/images/graemlins/frown.gif /forums/images/graemlins/frown.gif

Hindsight is a wonderful thing .... Beta information and Beta customer service knocks Yanmar into the oggin!



M
 
Re: You can start it on the hard.

With reference to the "defective exhaust installation" you cannot go wrong if you follow the schematics in the Vetus catalogue. The latest type water traps make it easy to get it right.

Also not necessary to regularly replace the exhaust elbow at regular intervals. Just remove and visually inspect plus carry out the leak test. Turn it upside down, block off the injection point, fill the gap between the two tubes with water. If any comes ot of the exhaust pipe you have a leak caused by corrosion of the inner pipe. If you do this every year you should spot it in time to replace before any damage.
 
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