What’s Behind the Engines and Gears?

Posted: June 1, 2014

Know your running gear, and why it’s important.

By: John Temple

Connected to your gears are the prop shafts, of course. The first concern is that they need to run from inside the boat to the outside of the boat, necessitating a hole or two in the boat’s bottom. Stuffing boxes do the job of sealing water out and letting shafts spin freely. Next, the shafts go through strut bearings, and then there are the props on the end. This is serious stuff to know about and take care of.

Most boats today have dripless stuffing boxes. All stuffing boxes are similar to a packing nut on a home faucet. If you have stuffing boxes that drip, it is important to watch the drip rate. Usually you want to see just two to three drops a minute, if you are seeing more, it is time to do some service work, because they need to be repacked. It’s not an easy job, but necessary.

Whether you have dripless or dripping seals, check them often while running. Two keys are to look at the shafts turning and look for any vibration or “wobbling.” Of course, look for any water leaking. If there is an excessive amount of wobbling, you probably have a bent shaft or a damaged propeller.

Every time you haul your boat, check the gear on the outside. Try turning the props by hand, and use a block of wood at the hull to test for trueness as the prop turns by. Things should all look good. Check the props closely for any dings or twists. If there are any big dings, I suggest having your props tuned at a good prop shop and try to get them close to “S” class, which improves the smoothness of your ride and increases economy. Make sure the strut bearings are not “loose” on the shaft(s). If the strut bearings are damaged, you must replace them. If you are not sure how to check this “stuff,” use your boatyard techs for help.

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