Gearbox engages forward gear intermittently

[ridgy]

Launched the boat today and found that forward gear would not engage everytime...ie you put it in gear and the engine revs but the propshaft don't turn.

If you give it a blast of revs then that gets it in about half the time, you just have to keep trying.

Odd because:
- Reverse engages fine
- Everything worked perfectly last season
- Not touched either the gearbox or the control cables at all
- Once it engages it works okay

I checked the gearbox oil and it was afew mm below the bottom mark so I shall top it up but would that make such a difference? I've checked the control cables and they seem to be pulling/pushing correctly.

Gearbox in question is a Technodrive TMC40 on a Vetus M204 engine.

Any thoughts would be appreciated.

Cheers,
Nick

 

[Gordonmc]

If its anything like a Borg Warner Velvetdrive, the oil (ATF) level is critical as the gearbox is little more than a hydraulic pump. The oil does much more than just lubricate gears. Symptoms are similar to clutch slip in a car but If you let the level drop too much you will lose all traction.
You will need to refer to a manual, but if you are losing oil the most likely cause is a leak in the core of the cooler into the raw water.
First thing to do is fill to the correct level.

 

[Evadne]

Apologies if I'm suggesting the obvious but these were the exact symptoms I had a few years back and it was a control cable problem in the end, although it had been preceded by a certain stiffness in the gear selector beforehand:
If you can engage forward gear reliably by disconnecting the cable and moving the gear lever manually then there's nothing wrong with the gearbox. If there is, then from what Gordonmc says not all gearboxes are the same and it may be better to consult your friendly local engineer. I can't help any further there.
If it is the cables, the commonest cause is the outer cable at the lever end not being held in properly. This can allow the cable to be pulled ok (reverse) but it pushes it out of its clamp when pushed (forwards) preventing full travel. This can be because the cable is stiff in its sheath and the effort required to dislodge it from the "clamp" is less than needed to operate the cable. Eventually it will stick, as like or not in forwards as you are approaching a pontoon, and you will not even be able to select neutral.