Gearbox woes?

[Smelly]

He lurks for ages and only comes back when he wants something I hear you cry... well rather than emailing the people concerned directly I thought I'd contribute!

 

I have developed a problem with reverse gear. Isuzu 35 with a prm120. About 60k hours. The box will have maybe 10k in drive.

 

When I engage reverse the engine starts labouring, it sounds like it did when it was struggling for fuel a couple of years ago (blocked fuel pipe). It gets worse with increasing revs. It's fine in forward gear.

 

It first developed after I reversed about 1/4 mile last week. I thought it was something on the prop but there's nowt there.

 

Fair to admit that I've not changed the oil for a couple of years so getting a new extraction syringe is first priority come pay day...

 

I wonder whether it might be the drive plate as when I last lost a gear that (and the mattress) was the culprit however thought I'd seek advice before I whip the box off.

 

Thanks in advance.

Edited July 26, 2014 by Smelly

[Guest]

I am not very familiar with these boxes, but seem to recall that the incorrect level of the oil can do funny things?

From memory you have a Vetus sterngear? If that is correct, mine did strange things once when a piece of nylon rope had got wrapped around the shaft between the prop and the sterntube. It was only a small piece, but had worked its way into the first 6mm or so of the neoprene bearing. It was certainly making the engine labour. Worth a look.

 

If you haven't got Vetus gear, please ignore my ramblings

 

 

Edited July 26, 2014 by Guest

[Smelly]

I have indeed got a vetus sterngland. Cheers Catty.

 

That looks like it was getting quite hot!

 

I'm guessing uncoupling the propshaft, pushing it backward and spinning it might dislodge the offending bit. Otherwise it's an out of the water job?

[Bloomsberry]

If the issue was the driveplate then wouldn't the symptoms be seen in forward as well as reverse due to the plate rotating in the same direction for both ?

 

Or is more torque required in reverse gear and a faulty driveplate could be ok in forward and failing in reverse ?

[Smelly]

Dunno, I just know that when my drive plate failed it ran in one direction and stalled in the other; I always guessed because it had taken a lot of energy in one direction. Certainly when we took it off the damper all bulged in one direction.

[Guest]

I have indeed got a vetus sterngland. Cheers Catty.

 

That looks like it was getting quite hot!

 

I'm guessing uncoupling the propshaft, pushing it backward and spinning it might dislodge the offending bit. Otherwise it's an out of the water job?

i got the nasty bit of rope out afloat through the hatch. It came off surprisingly easily, but caused a few problems!

[Smelly]

Wasn't rope; propshaft turns freely in both directions and, worryingly the gearbox has spat most of it's oil out since I last checked it in May. It's feeling expensive...