Westerbeke W50 Rear main seal while in the water

[felizcortez]

I have a Westerbeke W50 in a 1980 Tartan 37 and the rear main seal is leaking on the engine. I'm trying to figure out whether the rear seal is replaceable while the boat is still in the water. My primary concern is I would need to remove the transmission which disconnects from the prop shaft. I have a PYI dripless shaft seal on the boat and my understanding is that these need compression to maintain water tightness. If the transmission is removed, nothing is holding the prop shaft tight against the mechanical seal. Also to remove the transmission from the engine, the shaft will likely have to move back a few inches to provide space to wiggle it out.

Any thoughts would be appreciated.

[tkeithlu]

The PYI shaft seal is essentially an oil (water) seal on a propeller shaft. If you have smooth shaft in front of the seal, you can gently move the shaft aft without sinking the boat. Be sure that the shaft can't slide all the way out, which would spoil your entire day. Also be sure that you can pull the shaft back into place when you are finished with the engine.

The goal here it to not damage the lip of the seal. Installation gets around this problem by using a plastic collar that goes around the shaft and slips under the seal while you are pushing the shaft through it.

I've replaced the entire transmission with my boat in the water. Go for it.