Cheap Fix, Expensive Re-fix
Posted: May 1, 2014
1. Do I have to replace the drive unit in its entirety? How important is the skeg?
2. If I took a leather mallet to the prop, how would I know if I straightened it enough?
Straightening the prop: You might be able to straighten it enough to return somewhere in an emergency, but without a jig like the prop shops use, you’ll never get the correct pitch, diameter and blade curvature on all the blades. You might “eyeball” the prop and find you’ve done a pretty good job, reinstall the prop and discover there’s really no discernible vibration. Unfortunately, that’s a little guy named “Hope” running around in your head. The prop is not right, and here’s what happens if you leave it on. Because it’s slightly concentric after your repair, it now follows an elliptical path as it rotates. As you spin it by hand, you can’t really see it. Under load at 4500 rpm, the ellipse is violent. The prop shaft, sturdier than its ancillary components, begins to follow the ellipse, first wallowing the shaft seals, then the shaft bearings. The seals allow water into the gearcase. The water speeds the bearing and gear destruction. As the water comes in, the oil goes out, so in short order water is the sole lubricant. The top housing with the drive gears doesn’t even have the good fortune of having water cool it externally, like the lower case does while operating, so it heats the water that has displaced the oil, and shortly the gears seize. Normally when that happens, it snaps the u-joint and destroys the splines and probably the adaptor plate on the aft of the engine. What you’ve done by trusting your nonprofessional work is save $75 for a proper prop rebuild, while spending $3,500 for a remanned Alpha, plus engine removal, replacement of the plate, drive bearing and boots … let’s say $5,000 to cover a bunch of engine installation types. This scenario has happened in less than a day’s operation. False economy, but so easy to forget to yank the prop as soon as safely possible to have it rebuilt immediately. Time, it flies.
By the time this is printed, you will have probably resolved the problem. I might suggest, though, if you don’t have specific boat coverage, you check with your insurance agent to see if any of your homeowner’s coverage applies, or if anything from the rental-home agreement would help if the rock proximity were dangerously close to the pier.