Quote:
Originally Posted by jacklill120
I need to replace the drive plate between our Yanmar 4LH-TE and KM5A gearbox. The original Yanmar part (177074 03951) is very expensive but R&D do an alternative. However they quote two part numbers (48AD139 and
48AD102) stating that I need to measure the old plate.
'We make two dampers that will fit the 4LH, drawings attached. The installed length is either 29mm or 19mm.
Has anyone got experience (good or bad) of R&D drive plates?
Also has any one got an original drive plate hanging around that they could measure please?
We are crushing at the moment so I only want to remove the gearbox once!
Thanks in advance...
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It’s a tricky problem, your 4LHA is at the high end of the power/torque range for cruising yachts so the drive plate needs to be pretty good. I’ve replaced quite a few of the R&D
polyurethane driveline components and they’re definitely not a perfect solution ( they fail safe.... but they do fail). The Vulkan option is worth exploring but it’s unlikely to be much cheaper than the Yanmar plate ( some 4LHA’s had Vulkan from the factory). What is important though, regardless of what brand drive plate you install, is to make absolutely certain that the damper hub spline is clear of the root of the drive shaft spline. Any pressure at that point will load up the crankshaft thrust bearing with potentially destructive results. Ideally careful measuring will
rule out this possible mismatch but it’s just as easy to sling up the gearbox, put a layer of grease on the input shaft and do a dummy install, the grease will indicate how far or close the splines engagement is. Carefully inspect the splines for wear. If you go for the R&D or any of the aftermarket offerings make sure you keep the old Yanmar damper as a backup. I rebuilt a 4LHA during Covid and they are one expensive son of a gun for
parts, 4 liners and 4 pistons cost me over $4000 AUD and I still had to buy the piston rings.
Oh , that gearbox is no lightweight at 46 kg and Yanmar even provided a lifting eye on the housing at the balance point so you don’t get tempted to try and
lift it without a tackle.