TWL: (Another) Cautionary tale
We were out in the middle of SF Bay last weekend, when we stopped, turned
around with the gears, and then went forward. Very soon thereafter, there
was a loud "thunk" from the engine room and the RPM's suddenly went up on
the starboard engine. (oooo, that didn't seem good.....) When I went down
to investigate, it was soon apparent that the propeller shaft had slid out
of the coupling at the rear of the transmission, and down into the drip
packing. I could see still the top of the shaft, so we hadn't completely
lost it. (Whew, we weren't taking on water too badly, and saved some money
there!) Once again thankful for Vessel Assist card purchase. <g>
Tuesday I'll have a diver try to push the shaft back, which won't be easy,
of course. (Any special tricks or techniques for doing this in the water?)
However, the moral of the story is -- check those set screws on the shaft
couplings! This was not a standard operating check that I had ever thought
to make before.
Richard
49' Marine Trader Pilothouse (1978)
Twin Lehman 120's
SF Bay, CA
Richard Morrison wrote:
We were out in the middle of SF Bay last weekend, when we stopped, turned
around with the gears, and then went forward. Very soon thereafter, there
was a loud "thunk" from the engine room and the RPM's suddenly went up on
the starboard engine. (oooo, that didn't seem good.....) When I went down
to investigate, it was soon apparent that the propeller shaft had slid out
of the coupling at the rear of the transmission, and down into the drip
packing. I could see still the top of the shaft, so we hadn't completely
lost it. (Whew, we weren't taking on water too badly, and saved some money
there!) Once again thankful for Vessel Assist card purchase. <g>
Tuesday I'll have a diver try to push the shaft back, which won't be easy,
of course. (Any special tricks or techniques for doing this in the water?)
However, the moral of the story is -- check those set screws on the shaft
couplings! This was not a standard operating check that I had ever thought
to make before.
= = = = = = = = =
We lost a shaft coupling a couple of years ago when the set screw
disintegrated suddenly. Luckily, we were running around 6 knots, and the
rudder stopped the shaft from running back out. We had the boat lifted for
repair, rather than try to push the shaft back under water. Have the prop
and rudder checked for damage while the repair is completed. And have the
locking wire replaced on both sides if you have twins at the same time.
Taid's Inn is vintage 1965, so we were very lucky to find the right set
screw to replace the original. We purchased three so we have spares for
both engines now. Hopefully you won't have a problem there.
Checking the set screws is part of my spring maintenance check - I test the
wires for tightness and flex. It should be SOP for everyone with an inboard
engine.
Bob Davies
Toronto
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When I went down
to investigate, it was soon apparent that the propeller shaft had slid out
of the coupling at the rear of the transmission, and down into the drip
packing. I could see still the top of the shaft, so we hadn't completely
lost it.>>>>
Down under it's very common to have a taper, keyway and thread on both ends
of the shaft Then the coupling has a nut on the inboard end of the shaft
with a lock washer so the coupling can't come off.
What's more, when there is some wear at the stuffing box and stern bearing
you can "end-for-end" the shaft and have new bearing surfaces.
An old fishermans trick hereabouts.
Cheers
Glenn.
Another idea I have seen, place two hose clamps on the shaft between the
stuffing box and the coupler. Put them side by side, with the 'bulge of
each on opposite sides of the shaft (to keep the balance). Idea here is
that if the coupling does some off, the shaft will be stopped by those host
clamps, as opposed to running out through the packing box and leaving a
rather unfortunate hole in your boat where the shaft use to be ;-)
-al-
----- Original Message -----
When I went down
to investigate, it was soon apparent that the propeller shaft had slid out
of the coupling at the rear of the transmission, and down into the drip
packing. I could see still the top of the shaft, so we hadn't completely
lost it.>>>>
Down under it's very common to have a taper, keyway and thread on both ends
of the shaft Then the coupling has a nut on the inboard end of the shaft
with a lock washer so the coupling can't come off.
What's more, when there is some wear at the stuffing box and stern bearing
you can "end-for-end" the shaft and have new bearing surfaces.
An old fishermans trick hereabouts.
Cheers
Glenn.
I had a shaft back out of the coupling as I was tying up to a 82' Coast
Guard Cutter on the St. Johns river with a six knot current going the wrong
way. After some exciting moments we tied up in the opposite direction and I
was able to push the shaft back in place by holding on to the swim platform
and using my feet to push against the prop.
Where can one find set screws with square heads that have a hole drilled in
them for a safety wire? I find set screws but the steel is so hard I cannot
drill a hole.
Carroll Phillips, Endurance 43' Albin'79
Taid's Inn is vintage 1965, so we were very lucky to find the right set
screw to replace the original. We purchased three so we have spares for
both engines now. Hopefully you won't have a problem there.
Carroll Phillips wrote:
Where can one find set screws with square heads that have a hole drilled in
them for a safety wire? I find set screws but the steel is so hard I cannot
drill a hole.
Ours were located at a shop that specializes in rebuilding marine
transmissions. My marina looked after the repair for me, and I have no idea
what the name or location is - I believe it is located in Barrie, Ontario.
Sorry.
I'll try and find out for you.
Bob Davies
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the propeller shaft had slid out
of the coupling at the rear of the transmission, and down into the drip
packing. <<<<<
Your very lucky. With the responses I've seen it appears your misfortune
may help others. I originally was going to put a shaft zinc in front of our
stuffing boxes in case this were to happen to us (although I do check the
couplings every season). My theory was this would stop the prop from
hitting the rudder if the coupling failed. Our stuffing boxes are integral
to the hull with the fiberglass tubes part of the hull.
The other day a fellow at our marina sucked a shaft. His stuffing boxes
were the same design as ours. Well, the coupler (bolts fell out/broke at
the coupler to trans flange) hit this tube so hard it tore it loose from the
boat. All three bilge pumps were barely keeping the boat afloat. Luckily
this happened at the marina and he was able to be pulled immediately. It
appears the rudder stopped the shaft from pulling out anymore than it did.
Needless to say after seeing this, I double check the bolts on the couplers
and I do NOT use a zinc at the stuffing box. I'd rather straighten the
rudder, shaft and prop than call a mayday.
FWIW
Several boats ago my shaft couplings and shafts were drilled to accommodate
spring roll pins. Having a roll pin all the way through the coupling and
shaft was more positive in my mind. That was a gas engine direct drive
setup with 1" shafts and 15" wheels. Eddie Wright in Tacoma did that setup
( he's been retired for years now.)
Has anyone used such a setup in trawler with say 2" shafts and 26" wheels or
anything close to that size?
George
Nereid V, 1981 45' CHB Tri-cabin
La Conner, WA
the propeller shaft had slid out
of the coupling at the rear of the transmission, and down into the drip
packing. <<<<<
the propeller shaft had slid out
of the coupling at the rear of the transmission, and down into the drip
packing. <<<<<
Several years ago I started to feel a vibration on the port engine. Not
severe, but it bothered me, so at the next stop, I traced it down to the
shaft and the coupling. The coupling on our 60 ft DeFever was a large
diameter 12 inch steel wheel - almost like a flywheel - bolted to the
transmission. This wheel was about 3 inches thick and had several 1 inch
dia. set screw bolts around the perimeter to hold the shaft in the center. I
noticed that several of the set screws had backed out and were protruding
from the coupling. Also noticed that 5 or 6 of the bolts were totally
missing. None were in the bilge so they had been missing for as long as we
owned the boat. The surveyors, engine and hull, did not notice the missing
bolts some two yeas earlier. It just took two years for the three remaining
bolts to vibrate loose. The three bolts were weakly holding the shaft in
place. The shaft had a circular indentation where the set screws were
seated, which kept the shaft from pulling out of the coupling even with the
set screws loose.It also had a spline and keyway to keep it from spinning.
As soon as we returned to Seattle I had the boat pulled and the couplers
replaced with units which the commercial boats use. The yard emphasized that
the bolts should be checked frequently so as not to have the shaft pull
loose. This one has a large collar which is clamped around the shaft - like
a shaft zinc. The flat flange is then bolted to the plate at the
transmission.
Tragedy averted.
Don Sorensen
Esperanza
Seatle/Dallas
Sunday, April 18, 2004, 10:00:40 PM, Bob wrote:
BD> = = = = = = = = =
BD> We lost a shaft coupling a couple of years ago when the set screw
BD> disintegrated suddenly. Luckily, we were running around 6 knots, and the
BD> rudder stopped the shaft from running back out. We had the boat lifted for
BD> repair, rather than try to push the shaft back under water. Have the prop
BD> and rudder checked for damage while the repair is completed. And have the
BD> locking wire replaced on both sides if you have twins at the same time.
BD> Taid's Inn is vintage 1965, so we were very lucky to find the right set
BD> screw to replace the original. We purchased three so we have spares for
BD> both engines now. Hopefully you won't have a problem there.
BD> Checking the set screws is part of my spring maintenance check - I test the
BD> wires for tightness and flex. It should be SOP for everyone with an inboard
BD> engine.
BD> Bob Davies
BD> Toronto
I've seen a suggestion to install a shaft zinc on the shaft inside
the boat, if there is enough shaft exposed. This should prevent the
shaft from pulling out of the stuffing box, and should make recovery
easier.
(A zinc is suggested only because it is a readily available device
that can be clamped on the shaft - a similar fitting of any other
material would probably do as well.)
--
Peter Bennett, VE7CEI Vancouver, B.C., Canada
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver-webpages.com/van-ps