View Full Version : Stuffing Box and Propeller shaft maintenance

Dan Stephens
09-15-2002, 02:13 PM
I need to pull my shaft out and have it checked to make sure it is balanced and true. I was wondering if any of you guys had ever done this before if there are any tips you could give on this? I was also wondering what is supposed to be in the hull around the shaft if there are supposed to be any tubes or long bushings or what ever in this area between the stuffing box and the outer hull. Look forward to hereing from you!

Thanks Sincerely
Dan Stephens

09-15-2002, 07:58 PM
"Dan, look for any deep scoring or burnishing (scratching or discoloration) around the part of the shaft that passes through the stuffing box and the cutlass bearing. I'll assume your boat uses the "old style" stuffing box, consisting of a housing filled with wax impregnated string stuffing and a packing nut to tighten it against the shaft.

Normal surface variations are okay - you're looking for any worn or weakened spots caused by friction against the stuffing or bearing material. If you can hook a fingernail on a groove or if you can feel the diameter change between your fingers, the shaft is probably toast.

Packing nuts are often overtightened by a well-meaning owner in a effort to stop dripping from the box. The result is too much friction which overheats and weakens the shaft. Replace the shaft if you see anything suspicious, or have an experienced mechanic or machinist check it out.

Be sure to use the right diameter stuffing string when you replace your shaft, and don't spiral it around the shaft - cut the string to length and make individual rings around the shaft with the butt ends on alternating sides. Install a new cutlass bearing unless the old one is in top shape.

If you have a "dripless" sealed stuffing box, forget all this stuff about stuffing, but still check the rubber seals and look for shaft wear.


Dan Stephens
09-15-2002, 09:33 PM
" What about the area between the stuffing box and the outer part of the hull? what is supposed to be in this area? is there supposed to be a tube or something? and also what do they call the peice that is mounted underneath the boat that supports the shaft when it comes out of the hull? There should be some type of bushing or sleeve there too right? It looks as though there is a plastic or tephlon type bushing there now but it apears to be worn out and needs to be replaced. look forward to hearing from you again!

Dan Stephens "

09-16-2002, 06:34 AM
"I think you're referring to the shaft strut. The strut supports the shaft and is mounted just in front of the prop. It holds the cutlass bearing, which is usually rubber or plastic as you describe. Most have grooves to allow water to lubricate the surfaces as the shaft rotates. If the cutlass bearing is worn, it usually results in vibration and noise from that area and can damage the shaft if allowed to get worse.

The bearing is pressed into place using an interference fit. Most marine repair facilities or machine shops can replace the bearing for you.


Monty King
10-18-2002, 08:19 PM
" There is no support members in the area between the stuffing box and the bottom of the hull... in fact some boxes have the stuffing gland isolated from the structure with a flexable rubber hose so, the stuffing gland it's self does not interfere with the normal support of the shaft which is at the transmission output bearing and the cutlass bearing which is mounted in the strut, near the propeller as mentioned earlier. "