Yanmar 3gm30f lifespan and rebuild options.

[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.

[rslifkin]

I'd adjust the valves and do a compression test, leak down test, confirm good oil pressure at idle when good and hot. That should give you a good idea of the engine's health. If everything looks good, it's running well and nothing points to excessive wear or an issue then it should have plenty of life left in it.

[skipperpete]

Definitely adjust the valve clearances, keep a weather eye on the mixer elbow if it’s the OEM stainless steel one, if you see a line of corrosion between the elbow flange and the heat exchanger face, time to investigate that. Another thing that can really mess up your day is the thin external lube oil pipe that circles the block and supplies oil to the rocker gear and camshaft, even on a well cared for engine this pipe eventually corrodes through and dumps the lube oil into the engine tray or bilge. Inspecting the pipe is quite difficult especially where it disappears under the starter motor. At sea this is hard, bordering on impossible to fix so the path of least resistance is to buy a new one, paint it well and install it as a pre emptive strike. The banjo bolts need to go back into exactly the same places they came out of, the rocker gear one has a restricting orifice, it’s bad if it gets used elsewhere.
I rebuilt a 3GM at 7,000 hrs that really didn’t need the work, it was in excellent condition and could have gone back together with just a valve grind but the owner had already bought all the stuff for a rebuild. I just opened up a 2gm with a sketchy history and it had a buggered camshaft, oddly the valve cams were all good but the injector pump lobes were badly eroded so a very expensive fix. By all means, do a compression test but first, check the crankcase pressure ( blowby) at the oil filler cap.

[Mg451]

I'll have to investigate how to do a blowby I've never heard of it

[Mg451]

Is this the pipe you speak of

[Jammer]

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?

A rebuild on a 30 year old diesel rarely makes sense due to the costs and the parts availability both for the rebuild itself and over the likely post-rebuild service life. You would be looking at a repower.

What's the logic when it comes to Older engines that are running good still?

If it ain't broke, don't fix it.


The lifespan of diesel engines is limited by cylinder, piston, ring, and bearing wear. You're already aware of the usual indications that the end is approaching -- mainly oil consumption and low compression. This is a gradual process and it is possible to get hundreds or maybe a thousand hours out of an engine once it starts showing signs of upcoming failure.

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.

That's everyone. Before there were engines on sailboats people waited out the weather for days or weeks, kedged in and out of dodgy inlets, or anchored out and sent in the longboats.

[Mg451]

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

[skipperpete]

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?

It’s an easy test, start her up and run until warm, then unscrew the oil filler cap on the valve cover, the “blow-by” is the fumes that come out and the severity is how much puff you get. If it just a gentle hazy waft, that’s normal but if it blows the loose cap off and it’s smoky, that’s not good, (we call that engine a heavy breather). All engines have some crankcase pressure because there’s no such thing as a 100% perfect ring seal, they all have gaps and that leak goes into the crankcase, up the pushrod gallery and normally is dealt with by the PCV valve. Too much blowby usually implies worn rings but could also be a head gasket leak across to the gallery.
No, that’s not the pipe , the one you’re looking for is long and slim, it goes from the Left side of the engine then under the starter motor, up to a clamp on the rear of the cylinder head, then a banjo bolt to the rocker gear. Next it goes down to about the lift pump and along to the final 2 banjo unions…. Like I said, hard to inspect and even the tiniest bit of corrosion is cause for action, that 4mm diameter pipe has wafer thin walls and is entirely external.

[Tin Tin]

As well as other suggestions consider an oil analysis (gear box as well) then do another one in 50 hours, or follow the instructions - cheap and easy to do. Do another one 3 months before you decide to leave. They are about $30 - $40 postage paid.

[Mg451]

Good idea on the oil analysis. I add some liqiudmolly antifriction at every oil change think this will.throw off the results.

[skipperpete]

Originally Posted by Mg451

Good idea on the oil analysis. I add some liqiudmolly antifriction at every oil change think this will.throw off the results.

I use it too, that yanmar will take a long long time to wear out. A lot of larger engine pistons are “ molybonded “ from the manufacturer.

[Mg451]

Molly lock as in too much of the stuff is no good?

[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?

[rslifkin]

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?

That won't hurt it. If the engine is in good condition, cooling system is working properly, and the engine is being run under an appropriate amount of load then it should be able to run continuously until it's time to shut down for maintenance.

[rognvald]

Diesels need to run. Period. Most sailors run their engines at low rpm's and that is the worst practice for the engine. Once the engine is warm, run at higher rpm's over 2000 and then vary up and down every hour or so. My default is 2200-2300 to begin a run. Running at the same rpms every time or at low rpms is unnatural to maintain a healthy diesel. Allow the engine to cool at idle after a long run(10 minutes) and then shut down after revving quickly to 2500 rpm's. I would check your injection pump at a certified rebuilder if you have issues and if your injectors are fine. I had mine rebuilt after about 1500 hours and over 1000 hours later, it still runs perfectly with scheduled maintenance. Truck diesels regularly run over 500K in all conditions and then are sold to new owners who run them to to 7-800k miles. Some make it a miliion.
Bottom line: do your due diligence and run your engine. If there are no apparent problems, I would not replace it even if you have an ambitious trip planned. Remember, the diesel is an auxiliary form of power . . . we do have sails. Good luck!
Rognvald