Packing a stuffing box

[johnseattle]

Please, does anyone happen to know the correct packing size for the stuffing box on a 1978 Islander 28 sailboat? I've found plenty of good information on this site and elsewhere on how to do the repacking but the packing size is very hard for me to gauge. The shaft diameter is ¾" but I'm having difficulty measuring the diameter inside the compression nut because I can only slide it clear by less than a half inch before it comes up against a key on the engine'shaft coupling. The key won't move. Ideally I'd like to know the packing size in advance as I'm doing the job afloat and want to work as quick as I can. Thank you in advance.

[scottyt]

i believe but dont hold me to it, that a 3/4 shaft uses 3/16. i know my one inch shaft uses 1/4 inch.

make sure you by the real gore stuffing, and you might want to get all possible sizes ( the one you think plus one up and one down ) just incase, and sell the ones you dont need, for basicly the loss of the shipping

[floatsome]

Originally Posted by johnseattle

The shaft diameter is ¾" but I'm having difficulty measuring the diameter inside the compression nut because I can only slide it clear by less than a half inch before it comes up against a key on the engine'shaft coupling.

Sure it's not 7/8"? See also Stuffing box packing - Moyer Marine Atomic 4 Community I concur with having at least two sizes on hand. I'm after 3/16" for our 7/8" shaft (I suspect 1/4" is too snug), but it is not available locally.

[jjablonowski]

Ditto on several sizes available.
When I did mine (on the hard) I discovered that size recommendation on both the West Marine catalog AND the Universal diesel manual were wrong (oversize).

[SEMIJim]

Originally Posted by johnseattle

... I'm doing the job afloat and want to work as quick as I can.

Get a bicycle inner tube, cut it open and use it to "bandage-up" the shaft tube side of the stuffing box when you back the nut off to change the material. You should be able to all-but-stop water incursion. The other trick is silly putty in a baggie. Roll silly putty out, put in a baggie, stuff it into the shaft tube side of the stuffing box once the nut's backed off. (Note: The baggie is very important.)

Jim

[downeast450]

I did the 3/4" ss shaft on my Islander 28 last month and 3/16" is what I used. It is fine. I got 4 wraps in with ample threads left to grab the nut. I put them in one at a time and hand tightened between wraps. I tried a 5th wrap but was not happy with the thread space that left to grab the nut so I just picked the last one off. Good luck. It is really as simple and straight forward as it seems.

[johnseattle]

I'd like to thank everyone very much for all the good advice, it certainly helped. The repacking went very quickly and smoothly. I liked the idea of using a piece of inner tube to slow the inflow of water but in this particular case the inflow was fairly minimal - probably a few pints at most. What also helped lot was that a month ago I cut an access hatch in the cockpit sole. If I had had to do the work from the lazarette things would have been more difficult.