How to remove a gearbox?

[ridgy]

As in the title, I am removing my engine this weekend and am going to remove the gearbox to make it lighter/easier to manage.

How are they attached? Is it just a couple of bolts to undo and it pulls out, or is there more to it?

Thanks,
Nick

 

[vyv_cox]

What engine? Impossible to answer without knowing. Also, what boat? Also makes a big difference.

Splitting my Bukh 20 engine and gearbox proved impossible as I couldn't get to the lower bolts. There were about 10 bolts around the casing. I had to lift engine and gearbox out together. Whereas the Yanmar that replaced it looks better for access and I expect I could get the gearbox off if I needed to.

In some cases there may be insufficient space to pull the gearbox back off its splines, so you may have to move the engine forward.

 

[Poignard]

As in the title, I am removing my engine this weekend and am going to remove the gearbox to make it lighter/easier to manage.

How are they attached? Is it just a couple of bolts to undo and it pulls out, or is there more to it?

Thanks,
Nick

Mine is bolted to the rear of the engine by six [I think] bolts. Remove them and the gearbox will pull off.

That's the easy bit.

Getting the lower bolts out in a Twister needs a double-jointed midget who doesn't get headaches when hung upside down for an hour

ps like Vyv Cox, I also have a BUKH!

 

[MoodySabre]

Getting the gearbox off is probably the easy bit - a few bolts and slides out. Before that you have to undo the coupling and slide the propshaft back to give enough room to withdraw the gearbox. I don't know the configuration of an Elizabethan 29 but I think it is a longkeeler with the prop in a little gap between the keel and the rudder. In which case the propshaft may not draw back enough so you may have to take the prop off .....

All in all it could be one of those "ten minute jobs" or it could be easy and you might only graze a few knuckles and get minor back ache.

 

[ridgy]

Sorry, its a Vetus M204 with a Technodrive 40 gearbox. I should add that I am removing the engine whole, and then taking the box off afterwards so access not a problem.

Sounds like its just a case of undoing bolts that that should be OK.

 

[l'escargot]

Not a particularly difficult job once you have the engine out. Usually 6 to 8 bolts holding it to a bell housing. Sometimes the bolts vary in length or hold ancillary bits on, just remember what goes where.

 

[earlybird]

On my Beta 622 with a Hurth gearbox, the gearbox bolt heads are within the bellhousing and can only accessed by first detaching the bell-housing/ gearbox assembly from the engine block. Since the engine rear mounts attach to the bellhousing, engine removal is necessary.
I've got an idea that the Vetus might be similar.

 

[davidbfox]

Naive question I guess, but ...

Is the bellhousing joint sealing in the gearbox oil? So if not fully drained lots of oil will spill. Or is it dry and the oil is contained somewhere else.

I'm asking cos I need to to do the piston rings on my Yanmar YSM 12 and I'm weighing up whether it's best done in situ or whether I too need to get the engine out.

 

[vyv_cox]

Naive question I guess, but ...

Is the bellhousing joint sealing in the gearbox oil? So if not fully drained lots of oil will spill. Or is it dry and the oil is contained somewhere else.

I'm asking cos I need to to do the piston rings on my Yanmar YSM 12 and I'm weighing up whether it's best done in situ or whether I too need to get the engine out.

I would be very surprised if you can change your piston rings without taking the engine out. You need to disconnect connecting rods from the crankshaft to push the pistons up. It's possible on a car where you can drop the sump, but such a lousy job that it rarely pays to do it this way.

It would be a false economy not to do other jobs at the same time, rear crankshaft oil seal at the very least while you can get at it.

In most cases the bell-housing is dry.

 

[earlybird]

Naive question I guess, but ...

Is the bellhousing joint sealing in the gearbox oil? So if not fully drained lots of oil will spill. Or is it dry and the oil is contained somewhere else
I'm asking cos I need to to do the piston rings on my Yanmar YSM 12 and I'm weighing up whether it's best done in situ or whether I too need to get the engine out.

If I remember my old YSE correctly, the "bellhousing" is the gearbox and splitting the assembly will release the oil. Since it is a horizontal engine, removing the piston MIGHT just be possible in-situ, provided there is enough clearance at the sides, but, as Vyv says, much easier in the workshop. It has a wet liner, so this can also be replaced.
The main problem I encountered in dismantling my engine was separating the flywheel from the crankshaft.

 

[James_Calvert]

Two points for what they're worth:

When you've undone all the bolts and the gearbox still won't separate, have a really hard look around for the one you've missed. It'll come apart easily then.

Maybe not relevant to you, but (unlike Vyv who I think has/had a Sadler 34) I did manage to get to all the bolts on my Bukh in a Sadler 32. Had to prop the engine up when separating because the rear mountings were on the gearbox.

 

[wotayottie]

Naive question I guess, but ...

Is the bellhousing joint sealing in the gearbox oil? So if not fully drained lots of oil will spill. Or is it dry and the oil is contained somewhere else.

I'm asking cos I need to to do the piston rings on my Yanmar YSM 12 and I'm weighing up whether it's best done in situ or whether I too need to get the engine out.

I would doubt they have a common oil supply but the giveaway will be the instructions for filling with oil. If you have to fill the box seperately, there is a good chance (but only a chance) that you can take the box off without spilling oil. If you just fill both together than you definitely will spill.

Why not just empty the oil using a Pela?