Yanmar 3GM30 Exhaust Vapour and Tappets

[Reid]

I have a 3GM30 Yanmar that is raw water cooled in my Cole Nantucket 33. It runs well but the exhaust emits vapour or steam. I am sure that it is not white smoke. There is no sign of water in the oil. Does anyone know if this is normal?
I think I also need to adjust the tappets because they are noisy. Can anyone outline the steps to do this?
I bought my boat 3 years ago with 600 hours on the motor and it now has 800. Would this be considered a lot of hours for this engine. Externally it looks great ...no leaks and no corrosion. Cheers Reid

[djmarchand]

Reid:

The water vapor may an indication that something is restricting raw water flow. Or it may just be normal operation in high humidity conditions.

Two possibilities: The easy one is the raw water impeller is missing some blades, replace. The more difficult one is the exhaust elbow where the raw water is injected in the exhaust stream is partially plugged. You can get some idea of how bad it may be by disconnecting the hose and jamming a screw driver in to see if you get a bunch of scale built up. The only real solution is to replace the elbow.

Adjusting valves is pretty easy. Take off the rocker arm cover. Using a socket wrench on the big nut on the crankshaft, rotate the engine until the #1 cyl (closest forward) is on its compression stroke. This means that both valves, intake and exhaust are closed. Use a feeler guage. I think that the specs are .004" for intake and .008" for exhaust.

To adjust back off on the lock nut on the rocker arm and use a screw driver to adjust to spec. Lock the nut. It usually takes 2-3 times to get it right because locking the nut changes the setting a little bit.

Then rotate the engine until #2 is on compression, then #3.

Eight hundred hours isn't much for either the exhaust elbow or valve lash to be bad, but impeller life is more based on years, not hours.

David

[GordMay]

Greetings and welcome aboard the CF, Reid.

[Tiki 38']

Reid, I have two of these engines. They both steam from the exhaust,. One more than the other. I have learned to ignore it. I rely on the over heating alarm.

[westsail42]

I have the heat exchanger version of this engine. It does not emit water vapor. The only time it has is when it was overheating due to an exploded raw water impeller ;-).

In addition to what has already been said, vapor may depend on the size of you waterlift muffler (if you have one).

A larger than normal capacity waterlift muffler will have more water in the bottom, and tend to cool and condense any water vapor create by the mixing elbow.

If you do not have a waterlift muffler, then I would expect water vapor from the exhaust.

[Juniper]

I have a 3GM30F, I have cleaned the elbow in a muriatic acid bath before, just make sure it's cast iron, then flush it well in clean water, I just had to clear out the hose elbow,too,
If your not overheating under full load I won't worry too much about a bit of steam.

[Capitain Mike]

Originally Posted by djmarchand

Reid:

The water vapor may an indication that something is restricting raw water flow. Or it may just be normal operation in high humidity conditions.

Two possibilities: The easy one is the raw water impeller is missing some blades, replace. The more difficult one is the exhaust elbow where the raw water is injected in the exhaust stream is partially plugged. You can get some idea of how bad it may be by disconnecting the hose and jamming a screw driver in to see if you get a bunch of scale built up. The only real solution is to replace the elbow.

Adjusting valves is pretty easy. Take off the rocker arm cover. Using a socket wrench on the big nut on the crankshaft, rotate the engine until the #1 cyl (closest forward) is on its compression stroke. This means that both valves, intake and exhaust are closed. Use a feeler guage. I think that the specs are .004" for intake and .008" for exhaust.

To adjust back off on the lock nut on the rocker arm and use a screw driver to adjust to spec. Lock the nut. It usually takes 2-3 times to get it right because locking the nut changes the setting a little bit.

Then rotate the engine until #2 is on compression, then #3.

Eight hundred hours isn't much for either the exhaust elbow or valve lash to be bad, but impeller life is more based on years, not hours.

David

Yanmar recommend changing an impeller at the end of the season or after 250 hours personally I think that's is over doing it (but then they want to sell parts). If your engine is stationary all winter then you might find the impeller slightly out of shape (possibly) but if your in a position to run it that's good but you can always turn it over without running but not more than 10 seconds
otherwise you can flood it and get water in the engine. I change the impeller at the beginning of a new season. If changed at the end of the previous season its just sitting there getting squashed. Regarding actually changing the impeller take it out carefully then bend each wing/blade both ways and look where it joins the centre ring if there are no cracks etc. keep it as an emergency spare. If there are blades missing you must find and remove them.
otherwise you can get a blockage and over heat the engine. Don't forget if the exhaust elbow is blocked and causing a water problem that you can also get a blockage in the gooseneck if the pipe is breaking down internally

[Capitain Mike]

Originally Posted by Tiki 38'

Reid, I have two of these engines. They both steam from the exhaust,. One more than the other. I have learned to ignore it. I rely on the over heating alarm.

Is your over heating alarm wired into the ignition panel or separate?

[westsail42]

Originally Posted by Capitain Mike

Yanmar recommend changing an impeller at the end of the season or after 250 hours personally I think that's is over doing it (but then they want to sell parts). If your engine is stationary all winter then you might find the impeller slightly out of shape (possibly) but if your in a position to run it that's good but you can always turn it over without running but not more than 10 seconds
otherwise you can flood it and get water in the engine. I change the impeller at the beginning of a new season. If changed at the end of the previous season its just sitting there getting squashed. Regarding actually changing the impeller take it out carefully then bend each wing/blade both ways and look where it joins the centre ring if there are no cracks etc. keep it as an emergency spare. If there are blades missing you must find and remove them.
otherwise you can get a blockage and over heat the engine. Don't forget if the exhaust elbow is blocked and causing a water problem that you can also get a blockage in the gooseneck if the pipe is breaking down internally

Having had my impeller explode three times (each different seasons) and overheating the engine (once when I was approaching a busy anchorage in close quarters and it was blowing like snot), I would recommend changing it every season. Call it cheap insurance.

Also, when changing, be sure use the clear silicone grease (often supplied with the new impeller) to lube the pump housing.

[Capitain Mike]

Originally Posted by westsail42

Having had my impeller explode three times (each different seasons) and overheating the engine (once when I was approaching a busy anchorage in close quarters and it was blowing like snot), I would recommend changing it every season. Call it cheap insurance.

Also, when changing, be sure use the clear silicone grease (often supplied with the new impeller) to lube the pump housing.

Good Point
Also, when changing, be sure use the clear silicone grease (often supplied with the new impeller) to lube the pump housing.

impeller explode three times (each different seasons)
Did you contact the Yanmar technical department it sounds as though you have a problem somewhere.

There have been other threads on here about this.

http://www.cruisersforum.com/forums/...ure-23564.html

Impeller [Archive] - SailboatOwners.com

http://boatdiesel.com/Forums/index.c...P=1&Redirect=1

Yanmar impeller problems - uk.rec.sailing | Google Groups

Water Pump Impeller Failure - rec.boats.cruising | Google Groups

[Tiki 38']

Cptn Mike, it is wired into the control panel, when it overheats the alarm sounds. The same alarm that sounds after oil pressure drops after shutdown/startup. I know it works because once I forgot to turn the raw water seacock on. Why do you ask?

[Steve Thompson]

Reid
I have 2 3gm30s I have the workshop manuals also .If you need to lend them give me a yell Im in yor neck of the woods
cheers Steve

[Capitain Mike]

Originally Posted by Tiki 38'

Cptn Mike, it is wired into the control panel, when it overheats the alarm sounds. The same alarm that sounds after oil pressure drops after shutdown/startup. I know it works because once I forgot to turn the raw water seacock on. Why do you ask?

Extend it to the cockpit so you can hear it easily outside and have a backup installed also connect one into your muffler.

[Tiki 38']

Great ideas! thanks.

[Davey1000]

Watch out for sticking tappets on these engines! In my honest opinion the Yanmar manuals and the "Small Diesel Engine" manual are not terribly useful. It is as if they were written on the basis of dismantling and re-assembling a new engine (i.e. no corrosion, no rust and no seized parts) Recently I have been working on a Yanmar 1GM10 that I bought as a project - it seemed a good idea at the time and the way that the advert was contrived implied that with a drop of WD-40 down the bore it might become a runner. The alleged history of it discovered after purchase is that it was in a six ton boat and about five years ago its owner lost interest. The boat was neglected for five years and AFAIK the boatyard sold it (in lieu of rent?) to its new owner. The engine had been sitting in "rainwater" (bilge more like) for a long time so the new owner removed it and put it on eBay. Oh dear what a horror, job #1 was removing the gearbox and flywheel to make the thing light enough to carry to my shed. The drive plate was stuck on its splines so I had to use a power drill and a burr to enlarge the middle ventilation slot on the gearbox mounting plate. With the slot looking like Kojak's lollipop it was possible to rotate the gearbox mounting plate and unscrew the six drive plate screws using a tubular spanner. The two parts then separated easily. Inside the flywheel housing there was a lot of rust and white alloy corrosion but as rust is about twenty times the volume of the metal that it came from this was no big deal. The engine had a stiff point so the head was pulled. Amazingly the bore was excellent, no rust and no ridge, virtually as-new. During the dismantling, flakes of lime-scale were discovered inside the thermostat housing. IMHO these flakes were the cause of the stiff point. I had by now noticed that the stiff point occurred every second turn! Something had rusted the aft tappet. Presumably the lime-scale flakes caused the engine to overheat. Presumably the head gasket then leaked causing sea-water to lodge in the aft tappet tunnel. Possibly this was when the second previous owner lost interest in the boat. So far the flywheel has been power-brushed back to shiny steel and painted with Duracote anti corrosive red oxide. The drive plate has also been reclaimed. It is mind boggling to think that someone lost his boat on account of a bit of lime-scale but there you go! I don't really like raw water cooled engines but my old colleague "Captain Bligh" often waxes lyrical over the 1GM10s. In actual fact I prefer the other brand which is a fresh water cooled twin that is really no heavier. For open work boats where there are a lot of jellyfish, air cooling has a lot to recommend it.