White smoke from my 1gm

[frankfurder]

1983 cd 25d, motoring out I noticed white smoke coming from exhaust, water was pumping but less than normal. When I got back I checked the RW impeller and sure enough there was a missing vane. Could not fine The vane in the RW hoses, so I replaced the impeller. Cylinder head was pretty hot as well as water in the RW pump so I am wondering if there is a blockage somewhere? No high temp alarm but I wasn’t out but 20 minutes before returning to the slip.

After impeller replacement it seems like the RW flow was normal but I thought I would see what the board had to say? Caulder says white smoke is either low compression (pretty sure that is the case) or air or water in fuel. Recently changed fuel filters and can only get 2200 rpm ?

[gonesail]

not sure if you have one .. but the yanmar mixing elbows are always suspect with white smoke and steam.

[frankfurder]

Sure do have the mixing elbow, and I replaced it last year. Original 1983 elbow had a pinhole in the liner. Thanks for reply.

[wikakaru]

Finding that missing part of the impeller would be a good start. I believe the Yanmar 1GM is raw water cooled. That impeller could be stuck somewhere in the cooling system. You might try pulling the thermostat cover, mixing elbow, and zinc cover to see if you can find it in any of those places. Give the cooling system a good flush while you are at it.

Cooling system troubles are always difficult, because they are usually a combination of different small causes that slowly creep in over time. Take a good look at the whole system from your raw water through-hull intake all the way to your exhaust through-hull including the engine itself, try to figure out every single place that could be even a minor problem and replace or repair it.

• Check that the through-hull is fully open and not blocked from the outside with marine growth.
• Check that all the intake hoses are firm and cannot collapse under suction pressure.
• Check all hose barbs to make sure they are not corroded or that some previous owner didn't grind them away to make it easier to get hoses on or off. Alternatively a PO may have reamed out the inside of hoses to make it easier to get fittings on and off.
• Check that all connections have good, solid (not slotted) stainless clamps (I like the AWAB type) that are tight and that every connection is double-clamped.
• Check the raw water strainer for any clogs, either in the basket itself, or marine growth. Often strainers have 90-degree elbow fittings that are hard to inspect and easy to clog. Check the cork seal for a good fit and make sure there is no air leak.
• Check the raw water pump itself. The inside of the cover often wears down, leaving a gap between the impeller and the cover where water slips by and the pump does not work as effectively as it should.
• Check the T-fitting before the thermostat for clogs.
• Check the thermostat housing, remove the thermostat and make sure it opens at the correct temperature.
• Check for blocked cooling water passages in the engine block. As I said, this would be a good time to flush out the engine's water passages.
• Check the mixing elbow. I know you just replaced it, but perhaps the impeller has made its way there, or salt deposits have already blocked it.
• If fitted, check your water lift muffler for any accumulations that might increase back-pressure. They usually have a drain at the bottom for winterizing that you can open and inspect.
• Check your exhaust hose for kinks, gear stowed on it and crushing it, etc.

You may well find that there isn't one easy fix like simply finding a missing impeller blade or replacing the impeller. Given the age of the boat it could well be time to renew all the components in your cooling system--hoses, strainer, pump, barbed fittings, thermostat, gaskets, hose clamps, elbow, etc. Do it all at once and you may have another 10 years of good-as-new service from your cooling system.

If you don't have the engine manual, you may find this drawing of the Yanmar 1GM cooling system helpful: https://www.manualslib.com/manual/10416 ... 166#manual

Smooth sailing,

Jim

[fritz3000g]

Do you observe that you get white smoke at all RPMs? I've noticed that my 1GM produces white smoke at startup for a few minutes, then it mostly clears up. However, after warmup I get white smoke from 2400-2800 RPMs and black smoke above 2800 RPMs. I think my engine may have issues, so I don't think this is normal. Mine is in the shop, so I'll learn more soon.

It's my understanding that white smoke is usually unburned fuel resulting from bad compression, injector timing issues, an inability to reach design prop speed (i.e. motoring into waves or an oversized prop). There may be more reasons for it. If your engine starts immediately, then it's probably not compression.

It can also be steam, especially if you also get a temperature alarm light coming on sometimes. Anyone have an easy test to determine if it's steam or smoke?

[fritz3000g]

Well, I've got my boat back from the shop. They found that the camshaft was not really bent, but only the tip was. So they are suggesting that I:

- get the injector tested (done - works fine)
- clean out the injector port where it installs really well and replace the gaskets
- check the prop size (I can't get full RPMs)

if that doesn't work then either
- just let it run (keeping it low enough RPMs to avoid smoke) and hope it doesn't die on water
- get it rebuilt or repowered.

I also learned why my engine had trouble starting after pulling and putting back the injector.

When pulling the injector (the 2nd time) for inspection, I noticed that some round parts spread around the compartment that looked like they would fit into the injector hole. It looks like when I used engine compression to pop out the injector the first time, it also popped out some other parts as well. I think that's what caused slow starting after putting it back. Once I get replacement gaskets, I'll put it all back and expect compression to return to normal.

I also asked the Diesel injector shop if they had a way to test the 1GM compression, and they said no. It's impossible without an adapter which Yanmar no longer makes.

[frankfurder]

Thanks for the replies, after changing the rw impeller White Smoke has cleared up, probably steam. I still can’t rev past 2100 but have bled fuel ane engine runs fine, just not full rpm. Will live with it.

[Dick Kobayashi]

There is plenty on this board re 1GMs. But I suggest that a most likely source for low rpm is in the fuel delivery system, if the engine is running well. Going through each element of the fuel system may prove helpful and should not be too much effort. One simple thing to check is that the throttle opens all the way when you advance the lever in the cockpit. I had minor hangups with the lever mechanism and once with the wire that connects to the throttle which was hung up.

These engines are small and tough but loss of 25% of rpms is significant, for sure.