Yanma GM10 cold starting

[jwfrary]

One of the most common probs with this engine is the exhaust elbow. Although it is stainless, it is subject aggressive corrosion. If there is a hole in the double walled elbow it shoots superheated salt water steam into the head. This punches a hole in the head resulting in low compression. The GM10 is a good cold starter. My advice get a professional marine engineer on it at least for diagnosis so you don't go down blind alleys

Original ones aren't stainless but your right, it is an Achilles heel of these engines, but its also pretty well documented else where. Your also right that that stainless steel ones are also not impervious to corrosion, it a bit of misnomer that stainless doesn't suffer corrosion in exhausts.

I have engineered a few with custom hi rise elbows in heavy walled stainless pipe, with a replaceable mixer elbow in stainless off the shelf. - but its fairly involved and not that cheap compared to the off the shelf bits you can get.

 

[Boater Sam]

With reluctant to start diesels I use a blow lamp held about 2" away from the air inlet on a low flame to prewarm the air going into the engine.
Much better than using acetone starter fluid.
I did the same in winter with my 8HP sit up and beg Ford Anglia with its hopeless 6V system, always worked.

 

[vas]

About to remove mine and modify it rising the elbow some 150mm.
Would be interested in having a look how you did it!

Cheers

V

 

[peterhull]

Original ones aren't stainless but your right, it is an Achilles heel of these engines, but its also pretty well documented else where. Your also right that that stainless steel ones are also not impervious to corrosion, it a bit of misnomer that stainless doesn't suffer corrosion in exhausts.

I have engineered a few with custom hi rise elbows in heavy walled stainless pipe, with a replaceable mixer elbow in stainless off the shelf. - but its fairly involved and not that cheap compared to the off the shelf bits you can get.

Yes they need to be checked periodically and replaced if faulty. Cheaper than a new head. I speak from experience. Our Twister had this engine when we took it over. 1st or second season it gave serious trouble. Would not start. Took advice from Barrus the importers . We were advised to remove the head and send it to them for inspection. Came back with need to buy a new head £600 about 20 years ago!! My cousin had an elbow made in 316 SS and we removed it for inspection following year. Pinholes in the metal from corrosion already!! All directly cooled engines suffer. I remember I had 2 cylinder MD7 Volvo on my Vega and that had a cast iron elbow. Some used to treat them with a glass lining in an attempt to arrest corrosion.

With the Yanmar, we took the engine out of the boat and gave it a thorough overhaul. You can't mess about with this. You life may depend on it.

 

[jwfrary]

The heads are still available for the 1gm but the 2's and 3's are out of production, While expensive they aren't a crazy price I think around 900 quid, if you catch it early you may only need to lap the exhaust valve or possibly replace it for new - the heat exchanged models aren't immune either, but admittedly also not as venerable purely on the basis of the proximity of the elbow to the cylinders!

Joy of joy its on my list of new to me boat maintenance this year and I'm not expecting good things being that its done 3000hrs! I suppose I'm a glutton for punishment work on boats and play on boats!

 

[B58]

is it normal to find it hard to start these engines in the cold. i have just been helping somebody out who has just purchased a boat and to start the engine i had to remove the air filter and put oil into the inlet manifold to start the engine, i seem to remember having read somewhere of people wanting to fit heater plugs to these engines, is this why,or am i just ignorant of a starting procedure in the cold. thanks. Kieron

1GM10's have a cold start facility, when you shut the engine off the governor forces the rack into 100% excess fuel, once the engine starts the rack is pulled back.
the problem is that the cold start mechanism gets a bit slack, this is caused by the start spring slackening off (fig 15) this brings the rack back to fast, thus hard start.

To combat this you could replace the spring, or fashion a small shim 2mm thick drill a hole the same size as the bolt (fig 19) make it long enough so the the spring tail can be pulled over it, clamp down the bolt, and you have restored your cold start.

you can confirm that your cold start is slack take off the side oil filler you can see the fuel pump and governor rack, watch it when cracking the engine, if it fly's back before the engine started there's your problem.

 

[Porthandbuoy]

As coincidence would have it, I came across this while investigating my own 1GM10 starting problems.

1GM10 Governor Operation.

 

[DownWest]

Looking at your link, you highlight that the with the engine stopped, the rack is in the full fuel position. Nothing odd about that on old simple diesels. The Lister gensets I had to sort out were like that. Tends to smoke a bit at start as overfueled, but once they have a few revs, the governor pulls back and regulates it.

 

[vas]

curious, is that also true on GM (not 10/20/30) series engines?
and when you say stop, you mean by pulling the lever and stopping it or anytype of "stop" procedure? Mine is done by turning the governor all the way down.

 

[DownWest]

curious, is that also true on GM (not 10/20/30) series engines?
and when you say stop, you mean by pulling the lever and stopping it or anytype of "stop" procedure? Mine is done by turning the governor all the way down.

AFAIK, they are much the same. I have a 1GM and a 2GM20 in the shed and fitted a 1GM10 in place of the 1GM. Only difference is the bore and stroke + the output between the series.
Stopping all of them is by a 'stop' lever manually yanked. That overrides the govenor.