Getting the Shaft

As previously mentioned, we lost the port prop shaft during the delivery trip.  This occurred when we reversed the propeller to spin off some sea grass that had accumulated and was slowing us down.  Fortunately, the zinc nut on the shaft could not pass through the strut and the shaft stayed under the boat, but the end of it was inside the stern tube and could not be accessed from inside the boat.  This morning I had a diver down to the boat and he pushed the shaft back in for me.

One of the mysteries about the shaft problem was where the shaft key went.  This is a piece of 5/16" square rod that fits into grooves cut into the shaft and the coupling to keep the former from turning inside the latter.  The key should have been somewhere in the bilge, but it wasn't.  Improbably, it emerged from the shaft seal along with the shaft.  I had assumed that the last mechanic to pull the shaft put it back without the key.  I had gone through the trouble to take the starboard shaft out of its coupling and have that key duplicated.  Oh well, now I have a spare and the starboard side got new bolts and set screws in the bargain.

Getting these couplings apart was a bit of an adventure.  Being of light displacement, our boat's bilge is much shallower than that of a typical sailboat, but it has all the same stuff crammed into it.  Combining the tight quarters with some very stubborn bolts, the job looked impossible for many hours.  When confronted with this type of problem I usually end up at Home Depot staring at the tools I don't have and imagining how they could be employed.  In this case I bought about $150 worth (no such thing as too many tools!), but the answer lay in the $12 pipe wrench.  The first attempt with the pipe wrench failed for my lack of understanding how it works (well, have you ever used one?).  I think I would have nailed it on the first try with a chain wrench, but HD doesn't sell those.  Success came when I discovered that the pipe wrench's teeth are angled so that it only works in one direction.  You learn something every day.

Once I had it apart, I took it all over to General Propeller and they supplied me with a new shaft key and new set screws.  These set screws were drilled, so they can be wired and hopefully we can avoid this little exercise in the future.  One oddity was that all the set screws (two on each coupling) were 10mm, but one of the screws on the port coupling was 1/2.  Looks like maybe somebody couldn't get the screw out and ended up retapping it.  But the dimple on the shaft that the screw fits into wasn't any bigger.  I wonder if this could have contributed to the shaft slipping out.

The shaft seal itself was in bad shape and leaked heavily after the shaft was back in.  Fortunately, I had proactively purchased a spare on eBay and could replace it.  It had probably worn out and begun leaking during the delivery but wasn't noticed.  Turns out these seals are water lubricated and are supposed to be "burped" when the boat is put back in the water to avoid an airlock in the seal.  Even though it has a Volvo Penta part number (828416) stamped right on it, Volvo doesn't have any record of the part.  I've read elsewhere that this was equivalent to #828422, but this is for a 30mm shaft and mine is 32mm.  I'll keep an eye out for the 416's and buy any I find, but I should probably get a 422 just in case.

The port shaft seal is additionally challenged since it has to make up for an alignment issue on that side.  The way it has been explained to me, the stern tube and the strut are not aligned with each other, making it impossible to align the engine with both.  The correct solution is to rebore the stern tube, but that sounds like as much fun as getting a tooth pulled.  The more expedient remedy is to align the engine to limit the wear on the cutless bearings and accept the fact that they'll wear faster than usual.  With the misalignment the tolerances are so tight that the normal vibration of the engine transmitted to the shaft causes it to knock against the stern tube at some speeds which is not a pleasant sound.  Pretty much sounds like a hammer banging on the bottom of the boat.

Once everything was back together, I ran the engine at the dock for awhile, revving it up in forward and reverse.  Everything stayed together, but I didn't have the nerve to stress it in hard reverse.

The diver told me that I had barnacles growing on my propellers.  This was a surprise since I'd just had them treated with Propspeed.  I knew Propspeed wasn't an antifoulant, but didn't know that the barnacles could still adhere.  He said that if I ran my propellers periodically they would come off pretty easily in the wash.