Breaking Point: What Can Go Wrong With Your Yanmar?

These auxiliaries are an industry workhorse, but stay on top of that exhaust elbow.


If you want to know more about the little Yanmar chugging away in your sailboat, it helps to learn about this iconic engine maker’s lowly but ubiquitous GM series. This noisy, cantankerous, yet well-regarded machine will nonetheless take you anywhere you want to go. You just have to know how to treat it right—with respect, but a firm hand.

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Meredith Anderson
Meredith Anderson is a marine engineer and heavy diesel mechanic who owns Madame Diesel, LLC in Washington State, where she specializes in marine diesel engines and AC/DC Electrical. Meredith attended Massachusetts Maritime Academy, where she gained the foundation to become a marine engineer aboard commercial vessels from 120ft. – 554ft. She currently works full-time running her own business, traveling the nation with her training engines and fixing engines onboard her clients' boats. She uses her limited free time to work as a USCG 100-Ton Captain and Port Engineer onboard the Brig Lady Washington, teaches marine engineering part-time at Seattle Maritime Academy, and writes educational diesel engine articles for 48 Degrees North magazine and Practical Sailor. Her goals are to educate sailors and help them to complete the repairs needed for safe and happy sailing anywhere they want to go.


  1. I think I have solved the dissolving air filter problem K&N makes several styles of clamp on cylindrical air filters that end in a short length of essentially rubber hose, that can be clamped around the end of the nozzle of the air filter housing with a hose clamp. A K&N RD–0450 fit on mine. If I recall correctly it cost about $50 from Amazon, but there are many sources. I left the oil breather setup as Yanmar designed it. I orient the nozzle vertically so that none of the oil can drip into the filter. And the filter is easily seen to monitor for the need to replace it. I’d love to send a photo of the filter on the engine, but the boat is put away right now – not handy. Works fine. I’ve put several hundred hours on the engine since installing the K&N.

  2. A really thoughtful article, with new information and explanations. I repowered to a 3YM20 in my Atlantic City Catboat, and it is a “rock crusher”. Have had it since new about 15 years now. Routine maintenance each season, and it has never failed me. I was aware of the exhaust elbow issue, so I did replace it-but found it to be in fine condition anyway. I think following Yanmar’s operation guidelines regarding high max revs for 10 minutes at the end of a longer motoring session does extend the life of the entire exhaust system. This engine does have glow plugs, which might be helpful below 50 F, but I have never had to use them. Engine starts every time in a nano-second. Highly recommend this engine. It is quiet, and no vibe when above idle. Design has no dissimilar metals, so no anodes required. Thanks for the info!!

  3. A second on the K&N line of filters! Found a height & circumference that would work for my 2GM & ‘modified’ the rubber capped side; positioned over the intake port it works wonderfully! No more disappearing foam & easy to clean & re-oil the filter. Wish I had not lost the box or I would post the K&N model #… IF anybody has the info PLEASE post it up!!

  4. As I said, a K&N RD-0450 fit clamped on the air cleaner nozzle of my 3HM34F Yanmar. And I’m pretty sure the air cleaner housings are universal among the smaller older Yanmars. Plus, when I was researching a K&N filter, the staff at K&N was helpful in identifying which of their clamp-on filters would fit. Hope this helps.

  5. Thanks for your informative article. I have a 1984 3GMF. What do you know about the number of hours before overhaul for a well-maintained engine?
    Also, do you have a list of the components that are likely to fail so should be replaced? I replaced the gear cover gasket and understand that is a common wear item.
    Thanks, Tom