Hello Mark,

this is something you probably can do, considering your "automotive" background.

The main thing is to be meticulous.

First about your questions:

-You don't absolutely need to replace the VETUS coupling if it is in good 

condition:

       -the steel rods that hold the rubber "donuts" must not have moved from the 

steel hub, if so, replace the coupling

       -the holes for the bolts should not be damaged (ovalized), otherwise, replace 

the coupling

However, you will probably need to replace the donuts, easy to buy from VETUS.

If you need to replace the whole VETUS coupling, it is a standard coupling from VETUS, for a 35mm diameter shaft, with a key way for the C-drive input shaft BUT AMEL has the aluminium part machined in order it  "enters" the gear-box flange. You will see this when the gear-box is disconnected from the coupling (and if you compare with your new VETUS coupling).

Before touching the tools, make pictures and take notes (measurements of all the fittings, position of the nuts on the rubber mounts, position of the engine on the steel cradle, position of the shaft brake disc, etc...).

Start with disconnecting the hoses that could prevent you from moving the engine backwards on its cradle.

Then undo the coupling bolts and the engine steel supports' bolts (attaching the engine on the steel cradle).

Then move the engine backwards enough to remove the coupling bolts.

Undo the C-drive bolts of its rubber mounts. 

Remove these mounts. 

The C-drive will be held by the big rubber sleeve at the bottom.

Lift the engine just enough to be able to lift the cradle and remove and replace the YANMAR mounts with their lower nut set approximately like the previous ones were.

Re-install the C-drive mounts.

Then comes the alignment process.

AMEL uses a tool which is a steel coupling machined so that its aft side "enters" the gear-box flange (see pictures and drawing). You can also pre-install the new coupling and adjust the position of the mounts.

First bring the engine forward and make sure the coupling is centered with the gear-box flange, and can enter the gap in the flange. 

Then move the engine a little bit backwards and check that the gap between the flange and the aft side of the coupler is even all around the circumference. To adjust this, you need "thickness wedges" (used in the automotive industry) and play with the rubber mounts nuts to make the gap even.

Then bring the engine forward and tighten the bolts on the cradle and on the mounts.

The advantage of using the tool AMEL uses is that it is easier to install while checking the gaps.

If you need to make one, here's a drawing of the alignment tool for a YANMAR 4JH3-HTE.

The inside diameter (C-drive input shaft) is 35 mm.

The outside diameter is 100 mm.

The diameter of the part that enters the gear-box flange cylindric gap is 62.8 mm, thickness 3 mm.

You should use a VETUS fixed coupling for 35mm shafts, then have it machined to make the 62.8mm "plug" and drilled for the four bolts that should match the flange holes.

I think AMEL still sells the VETUS machined coupling, you will ask Maud when she's back from holidays.

Hope this is clear enough.

Best regards.

Olivier BEAUTE / ATLANTIC YACHT SURVEY

10 allée du Bout dehors

17000 LA ROCHELLE

Tel: +33 546 522 147   Mob: +33 674 028 243

 http://atlanticyachtsurvey.com

Now you see why I recommend Olivier to everyone. 

Hope this helps you. 

Mark McGovern 

SM 440 Cara

Deale, MD USA