Vibration When Shifting Kansaki (yanmar) KM3 Transmission

[F10]

Originally Posted by yalnud

Must be a pain in the arse to handle that beast when docking

Do not understand the comment. Boat easy to handle into the dock, especially now that I moved to a dock where I enter into the trade winds. Are you saying that because the transmission does not shift perfectly? I am used to things not working perfectly, just need to master some skills to overcome the imperfections...

[svJasmine]

I would be sure that putting the engine in gear doesn't cause the idle speed to drop below smooth. Try moving the idle up 50 rpm.

[F10]

Originally Posted by svJasmine

I would be sure that putting the engine in gear doesn't cause the idle speed to drop below smooth. Try moving the idle up 50 rpm.

I will give that a try and post the result. I checked the transmission shift linkage yesterday and everything looked good. The shift lever was going its full travel in both forward and rev. You could be right, might just be a idle rpm issue. One interesting thing is that when I get the vibration, it happens in both fwd and rev. When I don't get the vibration, it does not happen in either fwd or rev. So you would think if it were a cone clutch problem, it would occur in either fwd or rev at different times or maybe in just one, seeing the cone clutch uses different surface faces for the fwd and rev direction.

[F10]

I found these pics of what the cone clutch looks like:
J/30 Rhapsody #348: Transmission Disassembly & Clutch Resurface
Also Manual for similar Trans:
http://sagaforumet.com/yanmar-manual...apittel_7b.pdf

[F10]

Had a chance to work on the engine/transmission over the last few days. I wanted to change engine and trans oil so I started the engine to warm the oil. After warm up I shifted into forward and rev and had no grinding or vibration noise. I then changed both the trans and engine oil with the recommended 30wt (rotella 30 wt) and again started and ran the engine in both fwd and rev. Again no vibration or grinding noise. The yanmar tach showed engine running at 1000 rpm at idle and that is actually about 50 rpm higher than yanmar recommendation as I remember, so did not want to go any higher. A few years ago I adjusted the rpm to what it is now, as that is what sounded right for an idle speed. Any higher rpm sounds to high. I have a hand held tach and will measure the rpm with that when I get a chance (I understand yanmar tachs can run lower than true rpm). so with that I'll just keep an eye on the vibration to see if it surfaces again. Thanks for all your input.

[svJasmine]

You don't wanna go higher than that at all. Probably should be lower.

[a64pilot]

Originally Posted by svJasmine

You don't wanna go higher than that at all. Probably should be lower.

Yes, I'm thinking like 700 or so

[F10]

Originally Posted by a64pilot

Yes, I'm thinking like 700 or so

A few years back, when I had the rpm lower, the engine would stall going in and out of gear, so I bumped it up a bit. At a lower rpm than what it is now set at (1000 on the tach), the engine has somewhat of a vibration and just does not run smooth. When I get a chance, I'll measure with my hand held tach and see what actual rpm is.

[F10]

Follow up. I cleaned hull, prop and shaft and adjusted idle to about 900 rpm, anything lower and engine just did not run nice and harmonics were not good with boat hull. 900 rpm is within Yanmar spec for idle. I ran and shifted the engine and did not get the vibration, however several days before, I was getting the vibration on shifting. Also, this was interesting, went for a sail and after motoring to the outside mark, I put up sails, and put the engine in neutral to cool down (at least I thought it was in neutral). After cool down I pulled the shut off and the engine shut down but immediately started the vibration and rattling like marbles in the transmission. I went to the gear shift lever and found trans in gear, put in neutral and noise went away. Since I had the noise with the engine not running (and I do not think it was turning as the prop did not have the force to do that), seems to indicate a damper plate or trans problem, and most likely damper plate as failed springs would make that type of noise.

I am thinking I am having a failing damper plate. Also spoke with some reputable yanmar shops and they agree it could be the damper plate. Damper plate uses springs (or some use rubber) to take up the shock loads of the engine. Here is a nice video showing how a damper plate works (the vid is for car damper plate, but idea the same:
damper plate you tube - Bing video

I may have some failing springs or wear that creates the intermittent problem. When I get a chance I will do some more inspection and testing. I can see the damper plate and springs through the transmission bell housing and will inspect for damage. New damper plate is about $300 and not to hard to install- just need to split engine and trans at the bell housing- damper plate bolts to the engine fly wheel.
Regards

[Matsubob]

I hesitate to put a "damper" on that analysis, but the plate on a boat and a car serve entirely different purposes. The damper plate on a boat is very passive in comparison. It is only there for absorbing shocks in the drive train whereas the clutch plate in a car is there to also absorb shocks transmitted from hard gear shifting.
$300 is an awful lot to spend on something that probably doesn't need changing! That is, unless there are stripped splines or a broken spring. (highly unlikely)
It sounds more like the problem is fuel delivery related. Varying pressure in the injector pump, or an intermittently faulty injector? Rough idling brought on by the pulling of the cut off handle would indicate this.
Both the injector pump and the injectors can be disassembled and cleaned and reassembled without affecting performance as long as the factory settings are not altered. Tiny work, but very straightforward.

[F10]

Originally Posted by Matsubob

I hesitate to put a "damper" on that analysis, but the plate on a boat and a car serve entirely different purposes. The damper plate on a boat is very passive in comparison. It is only there for absorbing shocks in the drive train whereas the clutch plate in a car is there to also absorb shocks transmitted from hard gear shifting.
$300 is an awful lot to spend on something that probably doesn't need changing! That is, unless there are stripped splines or a broken spring. (highly unlikely)
It sounds more like the problem is fuel delivery related. Varying pressure in the injector pump, or an intermittently faulty injector? Rough idling brought on by the pulling of the cut off handle would indicate this.
Both the injector pump and the injectors can be disassembled and cleaned and reassembled without affecting performance as long as the factory settings are not altered. Tiny work, but very straightforward.

Matsubob:
Damper plates on boats and car serve the same purpose, that is to absorb shock loads when a high rpm engine (with pulsating output due to cylinder firing- especially in a small number of cylinder diesel) engages to a zero rpm transmission. Read more here:
http://www.cruisersforum.com/forums/...11-158958.html

[F10]

Did more investigating yesterday. Looked at all the springs in the damper plate and look at the plate and rivets. All looked good with springs tight and not broken from what I could see thru the vent holes in bell housing. Then I ran engine at idle, and in gear both fwd and rev at the dock. Never made any rattling noise. I also inspected the spline connection at the damper plate and all looked good.

I am sure the noise I have been getting (rattling) when shifting from neutral into gear was from the damper plate, and its springs. When tapping on the plate it makes a bell like sound, like what I would here. Since after cleaning the prop, and also lowering idle rpm by about 50, I no longer get the rattling sound or the severe engine shaking I would get when shifting into gear. So it must have been caused by the barnacles on the prop causing a severe pulsation when the prop was turning and/or an imbalance caused by the barnacles. I have had worse barnacles on the prop than what I had without the vibration, so not sure why this time it caused such a problem.

[Matsubob]

Thanks for your comments, F10. Without getting into technicalities, I may have overstated a bit, but my point was that the damper plate on a boat has much lighter duty than on a car. (and, technically, it is the flywheel and "harmonic balancer" that balances out the pulses on a multicylinder engine; the damper plate absorbs shock when applying power to the drive train).
All of that aside, the damper plate seldom fails, unless something inside, like a rivet or spring has broken. Based on the post, something of that nature would not cause the engine to not stop and begin running roughly, so I was simply saying that the symptoms point more to fuel/firing or other engine related issues
Sorry for the confusion.

[ErikFinn]

How about a worn cutlass bearing?

[F10]

Originally Posted by ErikFinn

How about a worn cutlass bearing?

Cutlass bearing was replaced about 5 engine running hours ago, and I checked it when I just cleaned the prop- all good. All is running well now so maybe the barnacles on the prop was the problem.