Jan 22, 2002
I remember one of you at least describing a successful way to improve the cooling of our cutless bearing with screwing a makeshift miniscoop above the inlet hole, but could not find it in the database.
I have found SS clamshell ventilators of the right shape, but much too large. Any other hardware that can serve? (eg, mast side exits for halyards, but here again, too large)
If using a SS tube suitably sawed and butterflied, what are the dimensions and shapes that have proven themselves effective and easy to fabricate?
Thanks for prompt answer as my boat gets into the water mid March, and I have much travelling in between.
Bert de Frondeville
1375 Jan 22, 2002
Bert- I think it was Paul W. who built the cutlass "cooler".
1378 Jan 22, 2002
Thanks Bill, I appreciated your quick response to Bert. I have been up to my gunwale in business since my return from Costa Rica and would have had to bypass reprinting that bit for some days.
The exact dimensions may have to wait a while as Sea Quill is now back in the water for her winter storage but the process to produce the scoop was fairly simple.
I took a piece of 1 inch stainless tubing (same as one would fabricate a stanchion tube from) about 1 Ĺ" long and simply cut it in half along its bias. The "working" piece of tubing was drilled, dead center with about a 3/8" relief hole (to prevent pressure build up that could conceivably pressurize the stuffing box). The base plate was created from a piece of 3/32" stainless plate that exceeded the footprint of the scoop by about Ĺ". Again a central hole of 5/8" bored dead center into the base plate. A slight, lengthwise roll was achieved in a plate roller to accommodate the curved surface of the deadwood. The scoop was then welded to the base plate. Four, attaching holes drilled to clear a # 10 x 3/8", stainless, self-tapping, screw were bored at each corner of the base plate.
I used a 5/8 " drill bit and carefully drilled across the center of the stern tube radius, just ahead of the cutlass bearing but no further in than the shaft. The scoop is then bedded into GE 5200 and attached with the four screws into predrilled, shallow holes.
The whole job, including fabrication took about an hour or so.
If I were to improve upon it in the future I may weld on a short, ĺ-inch sleeve that would insert into the drilled, cross-wise hole, just to add some better sealing of the raw fiberglass. I certainly painted the interior surface of the hole with a few dabs of epoxy with the current arrangement but the sleeve is a retrospective improvement on an idea that has certainly proved invaluable over the past 8 years.
1379 Jan 23, 2002
Thanks Paul for taking the time. It seems that the scoop is not that "mini", starting from a 1" tube, and that a 1 1/8" clamshell ventilator would fit the need, for a couple of dollars, without the SS welding (which I am not tooled for). So, Iíll reinvestigate that route.
I take it that you do not use the existing cooling hole (abt 2mm diameter, opposite to the screw and a bit forward). If so, why???
Thanks in advance, Bert dF
1380 Jan 23, 2002
If you intend to use a ventilator scoop, I do recommend that you still drill it for relief of the pressure.
If there was an existing hole on my boat, I never found it.
1381 Jan 23, 2002
Guyís- I donít have a "factory" cooling hole on my Ď79 model. Also, it seems to me that if using a PSS unit a little pressure from the scoop would help seal the rotor to carbon flange. Bill S.
1382 Jan 23, 2002
I also remember some one writing on adding a cooling tube, but it was not me.
We have not had a water cooling problem with the cutlass bearing. Maybe because we sail rather than motor, our rule is to sail until we are under 3 knots, then motor like hell until enough wind to sail at 3 knots or more again.
1383 Jan 23, 2002 9:17am
How do you know that the bearing needs cooling?
1384 Jan 24, 2002
Thanks Don, I too sail as much as we can, but I still find a blackened cutlass bearing, which some interprete as overheating, hence my studying better cooling. Found a suitable clamshell vent a bit under 1" chord for $2.99 by Perko (much better than the SeaDog $1.99, and cheap enough to avoid all that SS tube cutting and welding). Drilling a venting hole as urged by Paul makes good sense, but Iíll start small.
I also have to decide whether to enlarge the existing cooling hole (if it is a cooling hole, and not a missing screw...), or to drill a larger one forward as Paul did with the SS sleeve he recommends.
1385 Jan 24, 2002
Perhaps my response to fabricating my cooling scoop was borne from several motivations; I was running a machine shop at the time in the Caribbean and (1) metal fabrication was a daily activity. (2) The availability to catalogue parts from the US were subject to shipping delays and high customs duty. (3) My own tendency to design efficiency, I construct almost anything as if it were meant to last a lifetime, dictate almost everything I do with my sailboats.
It was obvious that a column of water being rammed into a ĺ-square inch opening at speeds ranging from 2 - 7 knots would certainly provide more than adequate cooling of the bearing but could just as easily fill the stern tube with water under varying pressures. As the tube is almost parallel to the waterline it only had two natural paths for relief, the bearing and the stuffing box. The obvious intent was to provide only "flow" through the bearing and not pressure to either.
My experience with PSS shaft seals, and at least one other, has been only to have found several owners switched back to the more versatile stuffing box after finding that the newer seal, once failed, has no underway emergency repair possibilities. In each of the two types I have replaced, the inboard sealing disc is held against the fixed seal with spring tension. I would hope that any cooling scoop used with one of these alternative shaft seal methods realizes that a ĺ" square tube of water, rammed at 7 knots may produce far more than 12 # per square inch of pressure upon the spring tension of the seal. My measurements for relief of that pressure seemed accurate at the time for a stuffing box (as Sea Quill is so equipped). I have never measured the resistant spring tension of the alternative packing units.
I suspect that if you are to implement the less labor intensive, clamshell vent as a reasonable substitute, it may just be good advice to indicate that simply cutting (or Drilling a relief hole) at the, aft facing, narrow-end of the vent, will significantly lower the pressure issue. Further, "flow" is encouraged at lower pressure by insuring the entry hole into the stern tube is nearer a half inch and forward of the bearing. Its hard to get an accurate measurement of the total of the exit slots of a bearing but the coolant flow source should be slightly higher than the exit capability. The collared zinc allows more exit laminar flow over the shaft than a bullet zinc which takes up most of the limited shaft exposure just aft of the bearing. (Its a shame that a bullet shaped zinc for a 1.5-inch shaft cannot be designed a bit shorter.)
As I have stated before, I am not an engineer who is capable of calculating the precise physics, (Don Bundy may be far more qualified to address these arguments), but my common sense is very acute, particularly when addressing issues of vessel safety. Drilling new holes in the bottom of the boat generally cause me a great deal of forethought
My cutlass bearing shows NO sign of wear or burning since it was last replaced in 1994. I estimate the screw turned 300 hours over that period. 80 of that, continuous on the trip from the Virgins to Bermuda. The packing of my stuffing box has been adjusted twice since replacement in 1992.
Another tip for those of you who have found that after several replacements of the cutlass bearing have caused the clearance between the fiberglass tube and the bearing to have become sloppy or uncomfortably loosened: most machine shops are capable of putting the new bearing into a lathe and tooling to produce a cross-hatched pattern, called "knurling", that effectively expands the diameter of the bronze as much as .030-inch dependent upon the depth the knurler is set to. The process renews much of the expected friction/locking surface between the two.This may prevent your reliance upon the, tiny, set screws alone to provide protracted, bearing position security. Sea weed, fishing line and casual or minor contact with debris places huge pressure upon the (turning) shaft-bearing contact surface. Many bearing have spun within the tube due to almost incidental contacts.
1395 Jan 24, 2002
Paul: thanks as usual! 2 questions, if I may:
Re: the two small holes I have on the sides of the fairing coming out of the keel to encircle the shaft. Are they both holding an excel screw that blocks the bearing sleeve at 3 and 9 oíclock? They are slightly offset longitudinally, and one of them seems devoid of screw, ie, a wire seems to go all the way to the bearing level.
If so, I need another hole to drive the water in, like the 5/8" hole you drilled. But the forward end of the bearing sleeve is well inside the keel itself, ie, the two vertical sides fwd of the fairing. Should I thus drill into that, and how much fwd of the bearing itself? a couple of mm should be enough? We sure donít want to create another path into the bilge, or the PSS body.
If you remember, where did you drill your own 5/8" hole exactly? And could it be a bit smaller (that will be taken care of by the sleeve, however)?
Thanks for taking the time in your busy world. bert dF
1406 Jan 24, 2002
The length of a new bearing of 1.5 inch ID seems to be about eight inches.. I drilled about an inch forward of the total depth of the bearing sleeve. I suggest that you check the length dimension of the 1.5 in dia X 2.0 in.(?) OD bearing for the length then add about 1-inch more for the cooling hole.
1780 Apr 15, 2002
In anticipation of an upcoming haul out, during which I intend replacing the original cutless bearing, Iím wondering if someone has a suggested part # or dimensions that I can cross reference in the West Marine or Boat/US catalog. Windfall has the original Westerbeke engine and Hurth gear. I believe the shaft is 1 1/8". Any direction will be appreciated.
Thanks in advance.
1781 Apr 15, 2002
I donít have the answer to your question, but in my boat the shaft is original, and 1.25, not 1.125.
Voyagerís engine is ready to go back into the boat, maybe tomorrow. I rebuilt the stuffing box et al today while sheís in the water. The resulting flood when the box is out is not bad at all - just a continuous dribble.
1782 Apr 16, 2002
My vessel has a 1 ľ" shaft, are you sure of the size.
1783 Apr 17, 2002
My shaft is 1 ľ". I used one of the following West Marine part #ís : 381558, 381566 or 381574. I donít remember the OD however. Probobly not the 2 ".