Replacing SD 50 Gear Set

[matauri500]

It appears that the upper gear set in my SD50 Yanmar Sail drive was not shimmed properly by Yanmar. The drive has 650 hours on it and started making a terrible grinding sound and was quickly disabled and we returned to Georgetown in the Bahamas under one engine.
Upon inspection it appears that the upper gears are not meshing correctly, engaging only at the ends and now slipping and grinding past each other. It appears that they are not shimmed enough to provide full contact between the gears.
Does anyone have experience with this problem? Can the gears be replaced without having to take the boat out of the water? If so how is this done? Does it require dismounting and moving the engine forward to gain access to the drive shaft to remove the worn gear or is ther some other way to accomplish this task.
Any help or guidance will be appreciated.
Thanks,
Doug
MATAURI 500

[NoTies]

Yes, it's possible but not adviseable, you are going to have an awful lot of metal in your oil that will need to be flushed out which can only be done properly on the hard.