While there have been a few design changes since my first outboard jet, for the most part they are still very similar. Yes, improvements have come over the years in regards to the liner, impeller material, cam-gate, grill bars, and a few less obvious innovations, but the basics remain the same. Instructions for greasing the drive shaft bearing have only changed in the frequency of when to do so. Earlier manuals recommended greasing the bearing after 10 hours of use and today’s instructions by Specialty’s Outboard Jet Division suggests that the bearing should be greased after daily use.

Even though this task takes less than a minute to perform, a few questions come up on this topic.

Q1: What type of grease is recommended?

Each jet unit is shipped with a hand held Jiffy Lube applicator and a tube of Lubriplate 630 AA or suitable substitute such as Quicksliver 2-4-C marine grease.  Specialty recommends that only water resistant grease with NLGI (National Lubricating Grease Institute) rating of ‘1’ be substituted for lubricating the drive shaft bearing(s).  The Lubriplate 630 AA is light in color and tends to show wear sign better than similar brands.

Q2: Why grease the drive shaft bearing so often?

I do not wish to over complicate this simple process, but find the best answer comes from understanding what is going on here. The Bearing Carrier has machined ports designed to allow grease to fill the bearing cavity and allow a grease overflow for heat expansion. As the drive shaft spins the impeller, bearing lubrication comes from the grease in the cavity of the bearing carrier. While this significantly reduces friction, heat does expand the grease and as it expands, it  enters the expansion hose.

The rough diagram above shows grease ports as they fill and overflow the bearing cavity.  After daily use, the cavity will require additional grease to fill the bearing carrier.  The lubrication process is that simple, pump just enough grease to fill the overflow hose. To minimize wear, keep the cavity full of grease and void of water.

Q3: How can I detect bearing and seal wear?

Once a month, purge your grease by slowly pumping additional grease into the cavity. As the grease exits the overflow tube, check the grease for color and consistency. It should be light gray and void of water. If the color has a dark stained and has water throughout its consistency, the seals should be replaced.

Another sign of worn seals is significant grease exiting the small hole on the opposite side of the jet pump. As the seals wear, they begin to allow grease into overflow ports opposite the grease zerk and overflow tube.

Q4: Can I use too much grease?

Slowly pump grease into the bearing zerk until the excess starts to exit the overflow tube, wipe off the excess and place the hose back over the zerk. This is all the bearings require after daily use. When purging grease after 30 hours of use, maintain light to moderate pressure on the pump. Do not underestimate the force of hydraulic pressure. Excess pressure as the grease enters the bearing cavity can invert or displace the seals. The hand held Jiffy Lube applicator that comes with the jet pump is unlikely to produce such pressure. If you are using a lever style grease gun, be careful not to force the lever excessively.  To keep correct service on your bearings, ease the grease through the zerk during each application.

Q5: How many bearings are in the bearing carrier?