I had Makana out of the water in May, mostly for a routine bottom-job.... but as my dripless shaft-gland was at least 6 years old, and their recommendation is to have the bellows replaced every 6 years.... I had that done too. In fact, my guess is it was more than 6 years old because mine did not have the integral "vent" which, I think, they started doing in 2014.
When the boat went back in the water, I asked them to let her hang in the slings for a bit before cutting me free. I think that's pretty normal, I mean I always run around and make sure there's no water gushing in anywhere, but... in this case, I wanted to make sure the dripless was really dripless.
It was, and remained dripless on the short low-speed jaunt back to my slip.
But the next time I went out, I heard a funny noise I'd never heard before and discovered it was my Rule bilge-pump, trying to draw down a surprisingly large amount of water in the bilge. Turns out, while it had been fine at low speed, at cruising speed the dripless was anything but - in fact it had sprayed water pretty much everywhere in the engine compartment. Fussing with it a bit, I found that the lightest touch on the graphite disc caused water to pour in. Ugh.
I called PSS the next morning and asked for advice. The yard I used is an authorized PSS installer, so I assumed they had done it right and I was missing something obvious Turns out, maybe not a good assumption. The person on the phone told me that the bellows has to be compressed to a given spec in order to ensure the appropriate amount of pressure between the graphite disk and the stainless-steel rotor.
For my dripless (1" shaft, 1-3/4" stern tube), the UNcompressed length ("C" in the diagram above) should be about 6-3/4" from the front face of the rotor to the back edge of the bellows sleeve. To achieve the correct pressure, the bellows should be compressed about 3/4", so the finished/installed length should be right around 6" from face of rotor to back of belows sleeve.
Turns out, the reason mine leaked if you looked at it hard was because it pretty much had no compression. It measured just a hair under 6-3/4" as installed.
Relatively easy to fix, it's simply a matter of removing the set-screws that hold the rotor in place on the prop shaft, move it to the correct location and secure it in place. There are a couple of things to bear in mind, though:
1) there are two sets of set screws in each hole. The ones that contact the shaft canNOT be re-used. They are "cup point" set-screws, and the cup is designed to compress when tightened to ensure good contact. The "outside" setscrews, used to secure the inner set-screws in place, CAN be re-used (once). So, keep track of which ones come out first, and set them aside for re-use. The ones that come out last could - in theory - be used to secure the new inner set-screws, but... set screws are cheap, and PSS will sell you a new set, so why create something to worry about?
2) it takes some acrobatics to hold the rotor in the right place with the bellows pushing on it. I had a 1" shaft-clamp, as a belt-and-suspenders backup against any slippage, and used that with some washers to sort of hold the rotor where I wanted it while putting the set-screws in place. Don't forget to use blue Loc-Tite on the set-screws to be sure they don't vibrate loose.
All tolled, it took about an hour to get the rotor in the right spot and secured. When done, the measurement in question is just over 6", which is pretty close to ideal.
I was surprised at how much effort it took to get it there, and so called PSS the next morning to ask if there was such a thing as "too much compression". The guy said it was theoretically possible to over-compress the bellows, but all it would do is accelerate wear on the carbon disk. He said that if you can "burp" the system by hand, it's where it should be. I tried and, lo and behold, no problem burping the bellows by hand.
Oh, and no more spray when running at cruising speed.
Could I have taken it back to the yard and had them "make it right"? Sure, and maybe I should have. But... I like knowing that I know how things are supposed to be, and now I know what the compression is supposed to be and how to make it right.
When the boat went back in the water, I asked them to let her hang in the slings for a bit before cutting me free. I think that's pretty normal, I mean I always run around and make sure there's no water gushing in anywhere, but... in this case, I wanted to make sure the dripless was really dripless.
It was, and remained dripless on the short low-speed jaunt back to my slip.
But the next time I went out, I heard a funny noise I'd never heard before and discovered it was my Rule bilge-pump, trying to draw down a surprisingly large amount of water in the bilge. Turns out, while it had been fine at low speed, at cruising speed the dripless was anything but - in fact it had sprayed water pretty much everywhere in the engine compartment. Fussing with it a bit, I found that the lightest touch on the graphite disc caused water to pour in. Ugh.
I called PSS the next morning and asked for advice. The yard I used is an authorized PSS installer, so I assumed they had done it right and I was missing something obvious Turns out, maybe not a good assumption. The person on the phone told me that the bellows has to be compressed to a given spec in order to ensure the appropriate amount of pressure between the graphite disk and the stainless-steel rotor.
For my dripless (1" shaft, 1-3/4" stern tube), the UNcompressed length ("C" in the diagram above) should be about 6-3/4" from the front face of the rotor to the back edge of the bellows sleeve. To achieve the correct pressure, the bellows should be compressed about 3/4", so the finished/installed length should be right around 6" from face of rotor to back of belows sleeve.
Turns out, the reason mine leaked if you looked at it hard was because it pretty much had no compression. It measured just a hair under 6-3/4" as installed.
Relatively easy to fix, it's simply a matter of removing the set-screws that hold the rotor in place on the prop shaft, move it to the correct location and secure it in place. There are a couple of things to bear in mind, though:
1) there are two sets of set screws in each hole. The ones that contact the shaft canNOT be re-used. They are "cup point" set-screws, and the cup is designed to compress when tightened to ensure good contact. The "outside" setscrews, used to secure the inner set-screws in place, CAN be re-used (once). So, keep track of which ones come out first, and set them aside for re-use. The ones that come out last could - in theory - be used to secure the new inner set-screws, but... set screws are cheap, and PSS will sell you a new set, so why create something to worry about?
2) it takes some acrobatics to hold the rotor in the right place with the bellows pushing on it. I had a 1" shaft-clamp, as a belt-and-suspenders backup against any slippage, and used that with some washers to sort of hold the rotor where I wanted it while putting the set-screws in place. Don't forget to use blue Loc-Tite on the set-screws to be sure they don't vibrate loose.
All tolled, it took about an hour to get the rotor in the right spot and secured. When done, the measurement in question is just over 6", which is pretty close to ideal.
I was surprised at how much effort it took to get it there, and so called PSS the next morning to ask if there was such a thing as "too much compression". The guy said it was theoretically possible to over-compress the bellows, but all it would do is accelerate wear on the carbon disk. He said that if you can "burp" the system by hand, it's where it should be. I tried and, lo and behold, no problem burping the bellows by hand.
Oh, and no more spray when running at cruising speed.
Could I have taken it back to the yard and had them "make it right"? Sure, and maybe I should have. But... I like knowing that I know how things are supposed to be, and now I know what the compression is supposed to be and how to make it right.
