This year I decided it was probably a good idea to inspect the stuffing box packing prior to launch since I had not done it since getting the boat in 2012.
Stuffing box
Before doing the inspection I searched the internet looking for any information on the stuffing box and drive system I could find. After a lot of searching I was not able to find anything. I even contacted the boat builder, but found out that they had a fire back in 2003 and all their records burned up in the fire.
Our stuffing box has a grease fitting on top of it. Dad said that we should give it “a few squirts of grease” after each use of the engine. It helps to keep water out and lubricates the system.
So I was feeling a little nervous as I started loosening the adjusting nut since I was not sure what to expect. Because of the access, backing off the adjusting nut took a little contortion but wasn’t too difficult.
Everything looked good and the stuffing box packing didn’t even look like it needed replacement, but when I went to tighten the adjusting nut back on, the entire stuffing box felt loose. That can’t be good!?
Adjusting nut loosened
Packing looks ok
When I torqued the nut back on, the whole thing moved back and forth
Based on some of the stuffing boxes I saw on the internet, I thought the mounting bolts for the stern tube went through the hull and attached to the stuffing box and that since the stuffing box was loose the bolts must have sheered. At this point I decided it was a good idea to completely disassemble and inspect the drive system. I first removed the bolts holding the stern tube in place. I was then able to separate the stern tube from the hull after removing a lot of caulking. The stern tube was threaded onto a tube that is embedded in the hull. I then separate the stuffing box from the hull. It was also threaded onto the tube that is embedded in the hull.
Bolts removed from stern tube
Stern tube separated from hull
15″ threaded tube that runs through the hull
Stuffing box separated
In order to pull the prop shaft I would have to either drop the rudder so I could pull it out the stern tube or pull the engine in order to pull it out the stuffing box.
Since dropping the rudder would have required the boat to be lifted about 4 feet (and cost money to have the yard do it), I decided to pull the engine.
Pulling the engine was uneventful. Separating the engine from the shaft adapter/dampener and removing the mounting bolts was not too difficult and with the engine out of the way we decided to take the opportunity to give the area a good cleaning.
Shaft adapter (right) and Dampener (left)
Engine pulled off its mounts
Engine on 4x4s
Cleaning 47 years(?) of engine grim
I customized an old wheel puller I had from a long forgotten project to pull the prop. Customizing the puller required cutting the 12” screw to 1.75” so it would fit between the prop and the rudder. It took an hour to cut through the hardened steel screw using a hack saw! After pulling the prop I was able pull the prop shaft and then remove the stuffing box and the stern tube.
Left to right – Stern tube, stuffing box, packing, adjusting nut
I brought all the pieces to work and blasted them clean.
All reusable pieces bead blasted clean
Also had the guys at work remove the prop shaft from the badly rusted shaft adapter. They had to use a lot of heat and a hydraulic press. After removing the shaft adapter I found that what I thought was an auxiliary pulley was in fact a dampener. After cleaning the prop, I found stamped on it, the manufacture (Michigan Prop). I contacted them to see if they had any information on the other drive system components. They didn’t, but put me in touch with a local business that might, AirMarine. AirMarine wasn’t familiar with drive system either, but did help me figure out that the stern tube was missing a cutless bearing.
Manufactured January 1982 by the Michigan Prop Company.
Stern tube with the old cutless bearing pressed out. Only the shell remained
Stern tube all cleaned up ready for the new cutless bearing
In addition to a new cutless bearing, it was obvious that we needed a new shaft adapter and dampener. I also needed new bolts (silicon bronze) for mounting the stern tube and the stuffing box. I found Deep Blue Yacht Supply out of Florida on the internet. I emailed them details on the engine (Yanmar YSB12) and the diameter of the prop shaft (1”) and they spec’d the proper shaft adapter, dampener and cutless bearing. Mike at Deep Blue was very helpful.
New shaft adapter (left) and new dampener (right, red)
Finding new silicon bronze bolts to mount the stern tube and stuffing box took more than I originally thought. I was not able to find a local source with on-hand inventory and I ended up ordering them online from BoltDepot.com. The new shaft adapter I.D. was 0.997” and the prop shaft O.D. was 1.007”. I bought a roll of emory cloth from the local hardware store and polished the prop shaft until it fit in the new shaft adapter.
Polishing the prop shaft ends
Shaft adapter end with shaft key
Shaft adapter fitted I also polished the prop end to insure a good fit.
Prop fitted
The cutless bearing comes in 2 lengths, 4” and 6”. I only needed 1.7”. Mike at Deep Blue Yacht Supply said it was ok to cut the cutless bearing to length as needed using a band saw. I was able to get 2 out of the one I bought. So I now have a spare.
New cutless bearing cut to size
Cutless bearing cut to clear hole in the stern tube that allows water forward of bearing for lubricating flow
Prior to pressing the cutless bearing into the stern tube I put it in the freezer (0 degrees F) 24 hour to cause it to contract. It pressed smoothly into stern tube.
Perfect fit
Reinstalling the drive system went fairly smoothly. I installed the new shaft adapter onto the prop shaft at home. The set screws on the new shaft adapter are at different angles to the key and at different points along the length of the adapter compared to the old one. I drilled (dimpled) the shaft at the area where the new set screws engage the shaft so they would engage the same way the old ones did. In order to try and insure the amount of the prop shaft that extended out of the stern tube was the same, I measure the distance between the end of the shaft and the old shaft adapter flange and insured the new shaft adapter was the same.
New set screw dimples
Assembled so the distance from the end of the shaft to the back of the flange is the same
Back at the boat we first reinstalled the stuffing box. I drilled and tapped new holes for the new bolts, I used Teflon thread sealant on the threads between the stuffing box and the tube that passes through the hull, and used 3M 4200 sealant.
Stuffing box reinstalled
We next installed the dampener on the engine side torqueing the bolts as the instructions indicated.
Cleaned the flange prior to assembling the new dampener
New dampener installed
The next step was to reinstall the stern tube. I re-tapped the existing holes, used Teflon thread sealant on the threads between the stern tube and the tube that passes through the hull, and used 3M 4200 sealant.
Stern tube reinstalled
We then ran safety wire through the shaft adapter’s set screws to prevent them from loosening and then reinstalled the prop shaft and the prop.
Safety wire
Prop shaft reinstalled
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Prop reinstalled
Next we installed new stuffing box packing.
New packing installed
Finally we move the engine back onto its mounts and loosely put new stainless steel mounting bolts in place. When we brought the shaft adapter to the dampener we found the mating holes to be about 25% of the bolt diameter off from one another. We had to lower the front of the engine in order to get the back of the engine to come up and properly align with the shaft adapter.
Engine alignment nut
Drive system completely reinstalled
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