Notes on the Cutless bearing

[Clyde A. Phillips]

Bob has a way of getting me to do things.  So here’s my input to the Cutless bearing.  I have helped put in a few new stern bearings while in the “commercial gang” before I was transferred to the “Newporter gang" at Dorchester.  So I can’t say I’m an expert but I have the audacity to put forth the wisdom of a half wit.

So Eddie is thinking of a new Cutless and has suggested he needs to know how to do it.  Let’s look at where the bearing is.  It is located at the after end of the stern tube, inside the tube and outside the propeller shaft.  The shaft is attached to the coupling just aft of the transmission and attached to its after end is the propeller.  The Cutless is attached by a couple of set screws that are set from the outside of the boat.  So, to get the Cutless out of the stern tube the set screws need to be loosened.  Therefore the boat must be hauled.  But loosening the set screws won’t allow the Cutless to come off the shaft—the propeller is in the way, so that, too, must be taken off.  Again, the boat must be out of the water.

Note that in the diagram that Bob so easily took from my site (that is one of the main reasons I launched those sites, so that everyone can take what they want) one sometimes not so obvious piece of the stern tube is the water intake system, consisting of two water intakes, one on each side of the deadwood.  Those intakes introduce water into the stern tube which becomes the lubricant for the shaft.  Note the “white lines” shown in the diagram on the interior surface of the rubber lining of the Cutless.  These distribute the water between the shaft and the Cutless.  The water also fills the tube to the stuffing box which, if not too tight will leak a little into the drip pan under the engine.  That water seals, lubricates, and cools the flax in the stuffing box.

So, Eddie, the first step in changing a Cutless is to haul the boat.  This being the case the best time to change a Cutless bearing is when the boat is hauled out to clean and paint the bottom.  Then remove the propeller.  This may require removing the coupling to give a little more room to take the propeller off the shaft.  This was no problem in our work boats which usually had a short section of shaft (a jack shaft) forward of the stuffing box and aft of the transmission.  You have to do what is needed in every situation and most every situation is different from the rest.    

[Eddie Offermann]

Thanks, Clyde!

I'm sincerely hoping that we inspect below this weekend and learn that the vibration and noise are due to a misplaced zinc instead of a bad bearing. The zinc had *just* been replaced by divers and the next time we started her up she had the problem - so it's possible the zinc is positioned too far forward or wasn't tightened down adequately and slid. If not, at least now I know exactly what we're getting into!

I wish this had come up when I had already planned a haulout - I'd hoped to put that off until at least this winter because I have a number of below-the-waterline projects on the Big List of Things to Do and want to do a lot when she does come out.