"Ask-A-Tech" reply

Use information here as reference only. Year, model, and accessory changes could change the result.

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Enginetype: Inboardgas

> motormodel: 

> Serialnumber:

> Configured: single

> boatmodel: Erickson 27

> Boatlocation: long beach, ca. salt

> Need: re-tightening packing nut

> TechQuestion:  need diagram and directions for replacing packing and re-tightening packing nut.

Our answer:

The packing is not a bearing. It's only purpose is to seal the hole where the prop shaft comes through the bottom of the boat. Shaft support is done by the transmission and the strut/cutlass bearing, located in front of the prop. If you are not sure when the packing was changed last, and it is leaking, it is best to replace the packing and start over so you can monitor it's wear pattern.

There are several types of stuffing box, (sometimes called a shaft log) so I will use the most common for example. They are all maintained about the same way. Also, the packing material diameter is very important. It has to match the original packing material diameter, as specified by the shaft log manufacturer. Sometimes a little trial and error, in selecting the size to use, is called for. You can use one of the old packings to match. That's if the one in there is the correct one in the first place.

The correct diameter packing material will fit relatively snugly into the packing nut. Too small a packing will not seal properly and too large will allow only two strands to be inserted.

After loosening the packing nut and jam nut, (see diagram:)  you can then pull the old packing from the packing nut. Use a pick or hooked pick to remove all of the old packing. There is usually three strands of packing installed but look for more and there could be only two.

After you have removed the old ones, cut three new packings by wrapping them around the shaft and with a razor blade cut the packing so that each one is exactly the circumference of the prop shaft. Then insert them carefully, one at a time, into the packing nut, making sure that you stagger the packing seams at 120 degrees. After each packing you may want to run the packing nut onto the stuffing box, as an aid to getting the packing all the way down into the packing nut.

Square style braided packing is suggested for shaft and rudder boxes. This material is made of all natural compounds; it resists heat build-up and will not score or mar the shaft. Graphite impregnated packing is not recommended because it can cause galvanic corrosion of the shaft. Teflon " impregnated packing, while affording excellent water-seal capability, can mar the shaft through friction. Use flax packing impregnated with animal fat, both materials known for their resistance to breakdown from heat, with an excellent performance record over many years and applications.

A break-in period is recommended on all new installations, during which excessive water leakage is allowed for two hours. This water flow allows the packing to conform to the surface finish of the shaft, and water to infiltrate all the voids of the packing for effective heat dissipation even after the unit has been tightened to its final seal. One drip or two per minute is considered normal leakage.

 

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