Yanmar 2GM20 Kanzaki Gearbox grabs when hot

[ShaunG]

I wanted to check if there was anything further i could do before calling in an engineer.

I have a yanmar 2GM20 with a Kanzaki geabox driving a shaft with a folding prop.

When the engine and gearbox is cold the boat shifts into ahead without any problems.

However, after a run of about 30 minutes i return the gearbox to neutral and all is ok. On attempting to put it in ahead there is an almighty clatter as though ahead is not engaging fully or the cones are 'grabbing' releasing and then 'grabbing again' i can get over this by sometimes applying throttle very slowly, or in other cases very fast and harshly. (astern is continues to wrok well)

i intend to replace te oil this weekend with the reccomended SAE30, however i suspect this wont' make a blind bit of difference.

has anyone had this before or have any ideas on what i can check before i get an engineer to remove the gearbox at ££££££

Thanks all

 

[vyv_cox]

It may be that the cable is not pushing/pulling the lever fully home. Try disengaging the cable when the engine is hot (suggest you don't do this in a marina!) then engage the lever on the gearbox by hand. If this is successful adjust the length of the cable at the Morse control end to match the point at which you can push the lever.

Before this it could well be worth checking that the oil level is correct.

 

[ShaunG]

thanks vyv, i have checked the engagment and all is ok (twas my first thought) The oil is on the max mark, although it does feel a little thin for SAE30 and does have a slight tinge of burnt smell

 

[colvic987]

thanks vyv, i have checked the engagment and all is ok (twas my first thought) The oil is on the max mark, although it does feel a little thin for SAE30 and does have a slight tinge of burnt smell

sounds like wrong oil in gearbox, or not been changed for years and lost its viscosity etc.

 

[charles_reed]

I wanted to check if there was anything further i could do before calling in an engineer.

I have a yanmar 2GM20 with a Kanzaki geabox driving a shaft with a folding prop.

When the engine and gearbox is cold the boat shifts into ahead without any problems.

However, after a run of about 30 minutes i return the gearbox to neutral and all is ok. On attempting to put it in ahead there is an almighty clatter as though ahead is not engaging fully or the cones are 'grabbing' releasing and then 'grabbing again' i can get over this by sometimes applying throttle very slowly, or in other cases very fast and harshly. (astern is continues to wrok well)

i intend to replace te oil this weekend with the reccomended SAE30, however i suspect this wont' make a blind bit of difference.

has anyone had this before or have any ideas on what i can check before i get an engineer to remove the gearbox at ££££££

Thanks all

I had exactly the same problem with the box on the 2GM20, until I totally lost forward gear as well.
Removing the sterngear and taking off the box between tides at Castletownberehaven, I stripped the box and found the actuator cam had worn on the one side - reversed it (expecting to have no reverse) and all was well - all gears back again.
Many and diverse were the "expert" opinions on the reason for the fault.

 

[ShaunG]

Hi charles, are you talking about the selector fork that sits in the middle of the drive/clutch cone? If so, it would make sense that drive is only just engaging although the external selector is moving all the way. Fingers crossed I can avoid a big bill, just found out the drive/clutch cone (my real thoughts) is £300 + vat. I will try everything before forking out for a new cone

 

[r_h]

I had exactly the same problem with the box on the 2GM20, until I totally lost forward gear as well.
Removing the sterngear and taking off the box between tides at Castletownberehaven, I stripped the box and found the actuator cam had worn on the one side - reversed it (expecting to have no reverse) and all was well - all gears back again.

Thank you! I also have the same problem and was considering a thicker oil to stretch a little more life from the gearbox - it works fine when the engine's cold, but is a problem when it's hot...

... but I'll take a look at the actuator on the next visit to the boat (it's in Greece).

 

[charles_reed]

Not the selector forks, but the little cam on the inside of the box, from the external actuating lever, which moves the selector.

It is kept in place by a pinch-bolt and reversing it is a very easy thing to do.