Yanmar 3gm30f lifespan and rebuild options.

[MerMike]

The pipe in question is part no. 1 in the diagram. It's a bugger to replace.

[LAGERTHA]

All good suggestions throughout this thread. I ran the same engine OEM for 30 years without anything major. They love to run, very dependable, always started on the first key turn. What tends to go after a bit are the hoses. Rather than replacing or rebuilding for now I recommend in addition to the recommendations in the previous posts to replace your motor mounts, hoses, filters, and impeller. Before your next voyage, replace your fresh water pump. Have an extra starter, as a backup. I feel you will do better with these steps as opposed to replacing or rebuilding. I regret to say, that you will likely be in better shape taking these steps as opposed to chancing a rebuild or replacement....if you went in that direction, I fear the quality of workmanship. You have a good uncomplicated engine there. You know how it sounds and feels. In thirty years, my engine never smoke either. As you may expect, I say keep that baby and continue to pamper it.

[Goodxcharly]

Just go to 1st world countries and you won’t have any problems.

[Cheechako]

Originally Posted by Mg451

I've got a downeaster 32 with a 94 yanmar 3gm30f. It has unknown hours on it when I bought it and I've put 3k hours on it. The engine is designed for 10k hours. I can only assume I'm up there in hours. I So before I set off for a third world country I'd hate to have a major problem some where else. I was wondering if I should get a rebuild or replace it even? I know it sounds silly. The motor runs great doesn't smoke I change the oil every 100 hrs etc. I was thinking about getting a compression test and adjusting the valve lash to begin. What other test can i do to give me indicators? What's the logic when it comes to Older engines that are running good still? I'm not a pure sailor I rely on my motor ALOT to run inlets and to get where I got to be when the winds unfavorable etc. Before I get bashed for that just wanted to stress the importance of a motor for me and the way I use my boat.

I had two of those engines in a 1992 Catamaran. So, close to the same time frame as yours. Both engines failed with less than 2500 hours. IF you do rebuild, just buy the Yanmar piston + rod assemblies, don't try to reuse. The piston lands have a tendency to crack below the last ring. When it gets bad enough you start to experience hard starting and/or low power.

[ewsponberg]

Mg451, here is a datapoint for you. Our boat, Corroboree, is a custom 35' wood-epoxy sailboat of my own design, built for my Michigan client in 1986-87 in New Zealand (he was moving to Australia for a few years). I specified a Yanmar 3GM30 diesel, so raw water cooled, and this was installed in NZ. She was shipped home to Michigan and sailed on the Great Lakes (fresh water) for 27 years. We bought her from the original owner in 2014 and had her trucked to Florida. The engine mechanic we had look at her estimated the engine had about 3,000 hours on her. We then had the engine fitted with a Yanmar heat exchanger to turn her into a 3GM30F, fresh water cooled engine.

We departed on a circumnavigation from Florida in January 2017, but by the time we got through the Bahamas we were noticing that she was burning through a quart of oil every 16-20 hours. We contacted the Yanmar distributer for the area in Miami and they recommended a certified mechanic in Puerto Rico. When we got there, his assessment was either rebuild this engine for about $12,000, or buy a new engine for $13,000. We chose to rebuild because this engine is mechanically governed whereas the new engine would be electronically governed (so less reliable and harder to fix). Also, the service side on our engine is the starboard side, whereas the new engine it is on the port side. We don't have good access to the port side of the engine.

The rebuild took 2 months, June-July 2017. We had the mechanic replace the pistons, rings, piston connecting rods, main bearings, valves, and engine mounts. Also, the block had to be bored out for new cylinder liners and new liners installed. The head had to be remachined to seat the new valves. The injectors were all inspected and serviced.

We have since completed our circumnavigation (June 2023) and have put about 1150 hours on the rebuilt engine. It runs just fine, and I expect to get another few thousand hours at least on this engine. We have Corroboree up for sale now.

That is our experience. I have no regrets about rebuilding the engine.

Eric

[Kello]

Regardless of your boat, age, skills, or anything else in life, this is now when sometimes we MUST navigate an inlet (or something) in unpleasant conditions and a reliable engine is the difference between keeping the boat and an unpleasant (or worse) experience waiting for rescue. You don't share enough info for anyone to give truly helpful advice so it is your problem to choose what is "helpful". Age, lifestyle, wallet, ... all are important. Can you lose the boat and continue "living"? Etc.

The (my) main problem with re-powering with a modern, efficient, reliable engine is that one lightning strike and you (the engine) are done. Next problem is that modern engines require expensive people and their sophisticated electronic devices to work on them, you mention 3rd world countries, good luck with that. Given your questions and curiosity level I would say you should rebuild the engine you have.

Ignorance is not bliss. Contact your local Yanmar dealer and request an electronic copy of your engines Service Manual, Parts Catalog, and Operation Manual. Read "The Alard Coles Book of Maintenance and Repair for DIESEL ENGINES" by Jean-Luc Pallas, if I remember correctly, 3 cyl Yanmars are used extensively for examples thru out the book.

Then (a few months later), combine the info you have about your engine's history and your personal issues and decide whether you should rebuild or repower. If you choose rebuild, then you will already know the parts you will need: sleeves, rings, bearings, springs, valve seats, oil pump (always!) ... and visit your local Yanmar dealer to see if the parts are available. If they are not, then your only choice is to repower, and, altho I love and respect my old Yanmar, you couldn't GIVE me a new one.

[skipperpete]

Originally Posted by Mg451

So here's another silly question...I met a guy way out at sea on the vhf we were becalmed together. He fired up his motor and steamed 72hrs to port and I followed suit. I've never ran my motor that long. It was within my oil change interval but I've never ran my motor for that long! Is that bad?

Nope, if its well installed and running ok, no problem. On one incredibly calm and windless trip from Darwin to Thailand , I was obliged to motor the entire distance, I even waited in a couple of glassy anchorages for wind…. Any wind at all rather than motoring day after day.

[sinnerman]

Originally Posted by Mg451

Googleing blow by testing a yanmar not seeing much any pointers where to begin how to learn about how to test this?

find the crankcase vent line on top of the engine and clamp it off with vise grips with woodstrips not ot damage the hose.

loosen the oil filler cap and set it back down on the oil fill flange.

Start the engine and see how much the cap "bounces" (relieving crankcase pressure...)

my two cents

cheers

[gregjm]

The one simple thing you can do to predict problems is an oil analysis when you next change the oil. Send it off to the lab and cut the filter open and look for metal dust. ANY engine, even a new one, can break down. MAKE SURE you carry a parts breakdown and shop manual for that engine. I have mine in PDF fashion on my tablet. If you need a mechanic having the manual is half the battle. Take spare injectors,belts, alternator, starter and make absolutely sure that your heat exchanger is clean and in good working order. Do check the compression ratios and if more than 15% variance investigate with a borescope. Blowby can be checked with a simple pressure gauge.

[Mg451]

All great info I just read the chiltons manual too. I'm gonna do a valve adjustment and compression test. And go from there. Says if you have low compression add a few drops of oil and repeat if the compression rises its bad cylinder if not it's valves. Seems to be pretty good start. It also mentions an exhaust back pressure test as the 2nd diagnosis point. Then fuel pressure test.

[Mg451]

My boat has a slight over hang and when in seas or motoring my exhaust outlet is underwater 90% of the time
.plus I have a lift muffler and probably a 6' run of exhaust hose plus a loop .I do get the black smoke beard and have suspected my boat was under power. So I'm gonna assume the test will show too much exhaust back pressure. I see the chiltons test procedure and haven't sourced the spacer with a tap for a Guage or thought about how to make one yet. Any one performed this test? Any pointers? IL like something semi permanent so I can run the boat get her to squat and replicate full load conditions..

[Mg451]

Ps looking and looking for a plug adapter to do the test on a yanmar 3gm30f I don't have an oldinjector to do the test. See lots of aftermarket adapters but none specify for a yanmar3gm30f. Is this the yanmar part YA10089?

[Mg451]

So I ordered a compression tester with an adapter that supposedly Is for a 3gm30f. I haven't pulled out the injectors yet but it looks like the injector cone out and then there is a precombustion chamber and heat shield and some gaskets that aren't all one particular the injector. When I insert the adapter do need to put in these parts..I assume I just need the gasket? I haven't actually pulled it yet so maybe it'll be overwhelmingly obvious when I do but I'm trying to get all the parts in dance that I'll need.

[geoleo]

gm30F is one of best engines ever

[Cheechako]

Originally Posted by Mg451

So I ordered a compression tester with an adapter that supposedly Is for a 3gm30f. I haven't pulled out the injectors yet but it looks like the injector cone out and then there is a precombustion chamber and heat shield and some gaskets that aren't all one particular the injector. When I insert the adapter do need to put in these parts..I assume I just need the gasket? I haven't actually pulled it yet so maybe it'll be overwhelmingly obvious when I do but I'm trying to get all the parts in dance that I'll need.

Does the gauge come with it? You need a screw on gauge not a press on gauge.