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Old 28-05-2021, 16:20   #1
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Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

Cinderella got launched this morning and I had an unusual event when I went to motor away from the hauling truck. The engine started right up, but when I put the lever into reverse it was very stiff and when I forced it into reverse I got a very loud rumbling/grinding sound. I put the lever back to neutral and tried forward - same thing. I eased it back and forth a few time, which loosened up the shifter cable and noise started to diminish. By the time the guys with the truck cast me off, the noise had pretty much stopped. (They don't wait around very long to see if your OK.)

I motored the mile or so to the yacht club and tied up at the dock. By then, everything was normal. I checked the stuffing box, which was leaking heavily and tightend that up a bit.

The boat has been out of the water nearly two years as we did not launch in 2020. Could this noise be caused by a dried out stuffing box? I looked at the diagrams of the Yanmar SB12 transmission and it has a wet plate clutch. Could the clutch have become dried?

I'm not overly worried as everything seems normal now, but I wonder what would make the drive train so noisy. BTW, the water pump worked fine.
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Old 28-05-2021, 16:42   #2
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

I don't know for sure what the problem is but from your fault description I can make the following comments.

It is highly unlikely to be the stuffing box (IMO).

The SB12 needs a fair amount of force on the transmission mounted shifter lever to move the heavy clutch plate (either way) to fully engage. I suspect the clutch plate wasn't fully engaging initially which was the source of the terrible sounds. If my suspicions are correct, either the shifter cable has got stiff (increased friction) or the clutch mechanism got a bit rusty over the two year layup.

If it doesn't come back I reckon all is good! Good to hear the water pump is also good.

EDIT - Disconnect the shifter cable and ensure the cable moves easily.
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Old 28-05-2021, 18:22   #3
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

What Wottie said.
Remember your gearbox is splash lubricated so it will have all dried out where the the shifter forks are as well. Not being run for 2 years ( assuming here) is hard on motor & box in salt air. Lube cables if its cable operated too. Enjoy your summer, its grey & showery in our part of the world.
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Old 29-05-2021, 05:47   #4
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

Thanks guys! Figures I'd get two solid responses from the best two contributors to Yanmar issues on this list.

I spoke with a buddy of mine and he made about the same comments, which supports your thoughts. I looked at the workshop manual and it is kind of thin in the transmission/clutch area and I'll confess it didn't make much sense, never having torn the thing down.

I'm going to assume all is well, but I will check the lubrication on the transmission cable.

On another note, two years ago I removed the Yanmar on-engine fuel bowl/filter and changed the fuel return line to run back to the tank, not back to the fuel bowl. This worked well in 2019 - I had zero issues with air in the fuel system. This spring I discovered a new benefit.

I wanted to inspect my bulkhead fuel filter and change the in-line fuel filter. Before doing so, I stated the motor and ran it - just to be confident that all was well before I got to messing around with the fuel system. After inspecting/changing the fuel filters I restared the engine. It ran momentarily then stopped. Turning the engine over by hand, I could not detect the "squoit-squoit" noise of the injector - a sure fire sign of air in the injection system.

I was about to grab some tools to loosen the fuel line to the injector when I thought about the fuel lift bulb I had installed upstream of the bulkhead fuel filter. Knowing that this device was getting old and that some of these do not last well with diesel I had inspected it while checking the filter - it's fine. I gave the bulb a couple of squeezes, which hardened it right up, apparently keeping pressure in the line. I gave the engine a couple of rotations with the hand crank and began hearing the "squoit" sound from the injector. I released the compression release and turned the engine over with the starter. It fired right up and has run perfectly since.

Should I now get any air in the fuel problems, I have a tool-less way to resolve the problem that takes about thirty seconds to do. Good to know!
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Old 29-05-2021, 11:00   #5
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

Do you have a folding prop? My boat makes a rumbling noise if I shift it into gear and only one blade moves into drive position. Shifting it forward and aft once or twice usually fixes the issue.
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Old 29-05-2021, 11:03   #6
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

Regarding the shop manual, for my 4JH4E, Yanmar has a separate shop manual for the transmission. You can reach out to a Yanmar dealer to buy a copy for yours should you want to have one.
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Old 29-05-2021, 11:39   #7
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

A good start would be to remove the cable from the transmission end and operate the lever to find out if it is indeed the cable. If it is stiff, simply replace it, rehabbing cables is a lost cause. Better to put your efforts into maintaining the new one.
While the cable is off, try moving the transmission lever by hand to detect stiffness there.
Loud noises that occur in gear often suggest damaged damper plates.
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Old 29-05-2021, 15:00   #8
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

My 2GMf sits for months at a time between cruises. Same kind of noise the first couple of times it's started. Quickly returns to normal for two or three weeks of heavy usage. I have been attributing it to the stuffing box (synthetic, not grease and packing). I you discover an issue with the cable, or linkage, I would be interested to know.
Regards, MLT
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Old 29-05-2021, 17:43   #9
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

I've studied the SB12 parts list, which is much more detailed than the workshop manual's photos. I confess that I still don't understand how this clutch and gear shift mechanisim work. However, I'm pretty convinced the noise was from the gear box, not the stuffing box.

I think the prevention of this may be to start the motor in gear (either one) and let it run momentarily. Then shut off the motor and switch to the other gear and start again. This should fully lubricate the two clutch plates. I'm speculating that operation would be normal after doing this. Alternately, be sure to run your motor at least once a year and put the engine in gear each time!

Note that I did start the motor in the fall of 2020 and again in the spring of 2021, but I never took the transmission out of neutral... and this old beast started on the first revolution every time.
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Old 29-05-2021, 18:17   #10
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

Good idea Homer except not sure how good it is for your cutlass bearing & stuffing box running dry. Guess if stuffing box well greased & you could squirt some glycerine in cutlass bearing if you didnt run for long it would be ok.
Running the engine in neutral should splash some oil around the gearbox anyway as the flywheel dips in the oil if you have the same gearbox as the Ys series IIRC.
having said that running it in gear would distribute the oil more/faster.
Do you store your boat with the engine on compression stroke? Thats a good idea on a single as it shuts off the combustion chamber from the salty air.
Yammer recommends it in one manual.
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Old 29-05-2021, 18:31   #11
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

Yes, I try to remember to top the cylinder when I shut down the motor, especially for long periods - like over the winter. This issue never ocurred with normal over-winter conditions and this is the only time I've kept the boat out of the water all season. Hopefully I won't have to cancel another season!
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Old 30-05-2021, 04:27   #12
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

Quote:
Originally Posted by Homer Shannon View Post
I've studied the SB12 parts list, which is much more detailed than the workshop manual's photos. I confess that I still don't understand how this clutch and gear shift mechanisim work. However, I'm pretty convinced the noise was from the gear box, not the stuffing box.
..........
The gearbox and clutch operation is pretty straight forward once you get your head around a couple of important aspects. Also the YSM manual has a far better description of the transmission than the earlier manuals. The gearbox is essentially the same on the YSE, YSB, YSM and SB engines with only a few very minor differences. While the attached page explains it quite well, just remember the following points as you read it.

The gearbox is a constant mesh type which means all the gears are always meshed together at all times. The shift lever does not move any of the gears at any time.

There are two friction discs inside the clutch plate assembly; one is connected to the forward gear and the other to the reverse gear. Note these two gears are concentric. The shift lever moves a intermediate plate (item 8 in the second attachment) one way or the other which causes the one friction disc or the other to be driven by the engine. When one plate is been driven, the other is free to rotate. Note, the two friction discs are always turning in the opposite directions except in neutral.
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Old 30-05-2021, 08:39   #13
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

That information helps, thank you. I suspect that the sliding disk/yoke and/or the cluch bearing surfaces in in the houseing got corroded. The boat is not near the ocean and it has been well covered, but normal time on the hard is seven or eight months. This time it was twenty. I'm going to consider the problem solved unless the boat shows me that it is not. I've filed your diagrams, too. Thanks.
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Old 31-05-2021, 18:20   #14
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

Went to the boat today and got the mast stepped. The possie at the dock did an excellent job. We hoist the masts using a boom and block and tackle on a massive flag pole. My mast, at 42' with a 6.5' drop to the keel, is about as big as the set up allows.

Before moving the boat I checked the transmission oil level - full - and shot a bit of lubricant into the cable. The shifting mechanism is still kind of stiff, but there were no strange noises from the transmssion. I'll investigage the cable and linkage further as time allows. Now I need to bend on the sails and tune the rig. As I've made a number of changes to the furling, flaking, and other areas of the rig over the past 20 months, I still have a lot of work ahead of me.
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Old 31-05-2021, 19:06   #15
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Re: Yanmar Terrible Rumble/Grinding Noise On Initial Engagement

Is the transmission oil clean?
Reason I ask is that if crankshaft oil seal leaks engine oil can find its way into the transmission. If it looks like engine oil & the level rises thats a giveaway.
Doubt thats your problem but it's worth mentioning.
I dont have any experience with dry storage & run motor in berth periodically.

The transmission may work its way free with use. I wouldnt sweat it too much unless the problem re-occurs.
Interestlngly I've had a couple of people wanting those clutch plates recently. I was surprised to find that they wear out but I suspect they only do with bad engagement as our 1980 engines ones are like new & AFAIK they were never replaced.


We do mast stepping the same way, only costs $15 at the club facility.
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