Horrible noise when engaging forwards from reverse

[tudorsailor]

I have a Yanmar, Model 4JH3-HTE. In my last trip I had a problem that seems only to happen when the engine is hot after several hours of motoring. I reverse into the berth (med mooring) and have to engage forwards to slow down and stop the transom hitting the quay. On several occasions the gear does not engage and there is a horrible grinding sounds as if there are coins in the gearbox. After a couple of attempts moving the lever from neutral to forwards, it finally engages sweetly and the fenders can be unsquashed.

When the engine is cold, it all works perfectly

The local mechanic has changed the oil which is now black

Has the clutch plate burnt out (if there is such a thing)? Why does the problem only occur when the engine is hot.

How easy is it to fix a burned out plate if that is indeed the problem???

Depressed

TudorSailor

 

[MASH]

Which oil was changed and is now black, engine or gearbox?

 

[charles_reed]

I have a Yanmar, Model 4JH3-HTE. In my last trip I had a problem that seems only to happen when the engine is hot after several hours of motoring. I reverse into the berth (med mooring) and have to engage forwards to slow down and stop the transom hitting the quay. On several occasions the gear does not engage and there is a horrible grinding sounds as if there are coins in the gearbox. After a couple of attempts moving the lever from neutral to forwards, it finally engages sweetly and the fenders can be unsquashed.

When the engine is cold, it all works perfectly

The local mechanic has changed the oil which is now black

Has the clutch plate burnt out (if there is such a thing)? Why does the problem only occur when the engine is hot.

How easy is it to fix a burned out plate if that is indeed the problem???

Depressed

TudorSailor

The gearbox has a self-energising mechanical cone clutch as on all the smaller Yanmar engines.

Mine lost forward gear completely.

A E Barrus' best guess was that the cone clutch had become glazed.

On stripping down the gearbox (between tides in Castletownberehaven beach) I found the forward/reverse gear selector had worn on one side of the fork. Reversing the selector fork eliminated the problem.

The symptoms you describe suggest that the cones in forward gear are not fully engaging - this problem is accentuated with hot, thinned oil.

 

[Jabamusic]

The horrible noise bit leaves me a bit uncertain if it is glazed cones which is what my 3GM30 suffered from recently. Symptoms for that were loss of power (slow and gradual over time) but more noticeably it would simply not engage a gear. ie no nice clunk!

The hot oil issue is familiar though, as when cold all was well.

I'm no expert here, but happy to pass on my experiences.

 

[VicS]

The gearbox has a self-energising mechanical cone clutch as on all the smaller Yanmar engines.

Mine lost forward gear completely.

A E Barrus' best guess was that the cone clutch had become glazed.

On stripping down the gearbox (between tides in Castletownberehaven beach) I found the forward/reverse gear selector had worn on one side of the fork. Reversing the selector fork eliminated the problem.

The symptoms you describe suggest that the cones in forward gear are not fully engaging - this problem is accentuated with hot, thinned oil.

I believe there are alternative gearboxes

KWB21 and KMH4A have multiple disc cluches

KM4A has cone clutches.

 

[tudorsailor]

Just for future interest, here is the rest of the saga. I had the gearbox removed and taken to gearbox specialists. They said not worth stripping the old box as they had unused box from an engine that had a saildrive fitted instead. They said I could have the new box for the same price as stripping and fixing the old box. New box then fitted!

Imagine my dismay when the sound returned when going into a berth only one month after using the new box.

Eventually got the new box taken off by a Yanmar man. He found that there was a ring that was worn where the forward cone engages. He replaced it. Then he had to suggest why this had happened. His suggestion is that the selector needed adjusting so that forwards was properly engaged before the selector then increased the revs. He suggested that the throttle was being engaged too early and this in turn stopped the forward gear engaging properly. With imperfect selection, then wear occured simply making the whole problem worse.

So far so quiet

TudorSailor

 

[Ruffles]

So far so quiet
...

Many years ago I changed the oil on our MS2A-D and found the old oil to be full of bits. Scared the life out of me when I looked at the price of parts! I strongly suspect it was wear on the selector forks as it looked like particles of brass. The oil is normally crystal clear.

Thing is the problem has never recurred though I have never adjusted the links. I presume the engine must have been run with the lever in a strange position.

Now I'm about to replace the teleflex control as it's worn and the red button is a bit knackered. And I'd really like get it right to avoid damaging the gearbox! Is there a process for aligning the levers?

 

[macd]

Now I'm about to replace the teleflex control as it's worn and the red button is a bit knackered. And I'd really like get it right to avoid damaging the gearbox! Is there a process for aligning the levers?

Your handbook (or maybe the installation handbook if it's different) should tell you. Some (talking generally, not Yanmar) need to be set up with a specified throw at the gearbox end; others need to accommodate the full throw of the gearbox lever, plus a bit of slack. It'll already be obvious to you that it's worth getting right, particularly (as in the OP's case), since it may initially appear to work perfectly well but will surely fail some time later. No doubt Vic, the fount of all such knowledge, will be along later to tell you exactly where to get the info you require if you don't have it already.

 

[penfold]

The only criteria is that the gear selection should be complete before any throttle is applied and that the throw(distance the cable-actuating lever moves) at the lever end matches the throw at the gearbox end; unless the throttle lever is knackered it should be straightforward to achieve.