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Stuffing Box Wrench Set, 2-5/16" Opening

Part #: M9163

The ideal wrench set for adjusting the stuffing box. Sold as a set of two.

Commissioning new boats, we discovered long ago that no standard wrench works well to adjust the stuffing box. After many bruised knuckles and wasted hours using generic wrenches, we found the wrenches we like best. They are easy to use in the confines of the engine compartment.

Both wrenches are for 2-5/16" nuts. They fit many Catalinas that use a 1-1/4" prop shaft. In fact, don't be surprised when you see the wrenches marked 1-1/4. This manufacturer designates the size of the wrench based on the size of the prop shaft rather than the actual size of the nut that the wrench fits! Caution! There may be early boats built before detailed records were kept that use a different manufacturer's stuffing box and therefore require a different size wrench. To be certain they are correct for your boat, you may want to measure the nut size on your stuffing box before ordering.

Why standard wrenches don't work:
• Crescent wrench: Jaws too large, handle too long, jaws too wide to fit the narrow jam nut
• Standard end wrench: When jaws are large enough for the nut, the handle is much too long to maneuver easily
• Monkey wrench: Jaws are at the wrong angle to fit into the bilge
• Pipe wrench: Jaws much too large and wide, teeth damage the stuffing box
• El Cheapo adjustable packing nut wrench sold by our competitors: Don't have any children aboard when using this wrench as you will be swearing a blue streak when it breaks and you bloody your knuckles against the rough fiberglass in the bilge!

Used aboard
Catalina 380
Catalina 385
Catalina 387
Catalina 390
Catalina 42


Caution! Never use only one wrench! There is only a piece of rubber hose holding the stuffing box to the hull. If you honk on the nut with only one wrench you are trying to twist the fitting within the hose. You will at least break the seal between the hose and the fitting. At worst you will damage the stuffing box hose and cause a substantial leak. Just hope someone is within ear shot when you do!

Note: Both these wrenches and the stuffing box is cast. Due to variations in the exact size of cast parts some filing may be required on the inside surfaces of the wrench to achieve a proper fit on your specific stuffing box. Sealing with a coat of spray paint will help prohibit any rust if desired.