Yanmar marine diesel engine repair

Troubleshooting and finally fixing a Yanmar 2gm20 marine diesel engine. Removal of Cylinder head, valve lapping, re-assembly and some oil pipe improvisation. I looked for videos of people disassembling the gm’s before I attempted this but could not find any. Perhaps this will better inform you what to expect if you are thinking about doing the same. Things learnt – Check mixer elbow every season. Check the oil pipe that runs hidden, behind the engine and before it spews all your oil into the bilge on passage one day!

I’d add, I’m an DIY guy, not a professional mechanic. I didn’t find this too hard and managed to expand my tool-kit, probably for less than it’d have costed to get the local mechanic to step on-board. If you have the confidence to do the same, I’m sure you’d find it as rewarding as I did, though obviously at your own risk! ๐Ÿ™‚

Happy sailing.



28 thoughts on “Yanmar marine diesel engine repair

  1. Hi Paul, yes the original elbow is as you say a pipe within a pipe yet I think it's not 100% necessary to stay with this original design which at the end does not prove to be so much reliable, why not welding a smaller pipe pouring the water say 10 cm far from the beginning of the elbow, sure this first portion will be hotter but who cares ? you do not have to touch it. or it's possible to create an external sleeve to cool it down too. i will make one and show you some pics, welding aisi 316 ss it's not so difficult after all if you have the right tools. A commercial ss curve costs about 5 โ‚ฌ in Italy…One more advice, the yanmar manual tells you to use/spread a special paste when reassempling the head gasket. Did you use it ? And if yes how ?

    thanks to everybody


  2. Interesting, helpful and informative. Many of the principles you covered would apply to any diesel marine engine of similar size, so thank you, and continuing good luck in general and reliable service from the Yanmar, in particular! Col, NZ.

  3. Brilliant! My 2GM has Exactly the same problem and I have been fretting for a day over the cost of replacement. I'm headed to the marina now with the kit to tear the head off. Fingers crossed Paul; you many have saved me thousands. Keep up the Great Work man. ๐Ÿ™‚ ๐Ÿ™‚ ๐Ÿ™‚

  4. You better clean your water passage ways before you crack you block because of over heating. Vinegar works well for this.

  5. I very rarely post comments, but I wanted to say big thank you for posting this video! You gave me the confidence to resolve my leaking valves and my engine is now better than it's ever been since owning the yacht for 7 years.

    I had similar symptoms as you-sooty exhaust, decreasing RPM, some smoke out the intake even, difficulty starting and these all got so bad I eventually couldn't start my 1GM at all. After watching your video all of these symptoms began to all add up and make perfect sense as to what was occuring in my engine. I found my exhaust mixing elbow had failed and both my valves (particularly the exhaust valve) had corrosion causing them not seal properly against the valve seats in the head. I'm so relieved to have this fixed, the parts weren't cheap (mixing elbow and head gasket and I replaced my exhaust valve as it was too corroded to clean up) but still cheaper than a new engine. Nice to know the engine is running correctly and I will be sure to regularly inspect the elbow so this never occurs again-in hindsight there were many warning signs of this condition developing.

    Thanks again!

  6. When mechanicing it's always good to include a magnetic recovery device or three. A magnet on a string or on a flexi head will usually make recovering dropped nuts and bolts much quicker especially when fishing in the bilges.

  7. Well done, friend. For your valve spring compression, place a wee but of wood under the valve head, and get a BIG ring spanner and place it over the top of the valve. Press down hard and get a friend to tease the collets out. A wee magnet on a rod (or wooden stick) helps retrieve them. It only takes a few seconds when it goes well. Thanks. TroyaE117.

  8. I've been building and repairing engines for over 40 years. I'm guessing you did this without a massive amount of knowledge on this actual engine. The way you approached it is brilliant, the best thing was you were able to think out of the box, learning by doing is the best way. First class work.

  9. Great video. This, along with your others, will prove very useful. I maintain 12 pieces of equipment powered by Yanmar diesels.
    I currently have one blowing fuel rich white smoke (and only running on 2 cylinders.) First thought was injector stuck open. Replaced and no change. Adjusted valves, no change.
    Wide open to any thoughts from you or anyone else.
    The motor was upside down for about 30 minutes in an accident.

  10. Wanted to let you know I appreciate your video, the humor and DIY attitude! I had done ours 14 years ago and it's time to do them again, you video was a good reminder of what to expect, even tho we have the heat exchangers to deal with…

  11. Very helpful video and job well done. As a fellow DIY type in process of replacing 3qm30 head gasket I found a lot of help here. I am curious what the overall time frame was from beginning to end including waiting on materials/parts. It always amazes me how long these projects take doing them in spare time. I find one of my biggest challenges in not rushing to see if the repair actually works. :-0

  12. Okay… 1,2,3 and you've managed to convince me I can do the same with my eyes closed (okay, maybe not with my eyes closed). At least I believe I can do it – not that I've had your exact issue, but you never know what might come up – there's been enough. Next time I won't be dialing the mechanic. I'll just watch your video again and plow ahead full bore! Thanks very much. Well done.

  13. 1. The pair of thingies you pull to free a valve retainer are called "keepers"; a collet is used to precisely clamp a cylinder from the outside. 2. Lapping valves is not advised. Valves expand with heat, so lapped area does NOT make contact when hot. Typically the seating region is too wide besides. Machine shop wiil grind all precisely for "pennies". Good luck.

  14. I have a yanmar 3gm, raw water cooled. I imagine its very similar to your engine. Around 19:25 you mention a workshop manual for this type of engine. Where did you find this manual? I've been looking online for a workshop manual specific to my engine or similar enginesย with no luck. Any leads would be appreciated. Thanks!

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