The prop shafts have been removed (they slide past the rudders) and we’ve given them a close look. The cutlass bearings are both still within tolerance, with the starboard bearing showing no wear. The port bearing has on the order of 1/8″ (3mm) of slop, not much really.
However, we are replacing both since the shafts are now out. The shafts show almost no cutlass bearing where.
But what they do show is a bit of scoring from slipping Spurs line cutters. The starboard shaft (above) has roughly a 1/16″ (1.5mm) scoring.
The port is a touch worse. If these were highly loaded shafts, with big engines, consideration would be given to machining the grooves to soften them, or even replacing the shafts. But with two inches/50mm of Nitronic 5o alloy, and just 50HP on average of force, these are still way oversized.
Posted by Steve Dashew (November 18, 2011)
November 18th, 2011 at 10:19 pm
Steve,
So glad to see a reasonable reaction to the shaft wear, rather than replacing them. Curious about the bearing though, 3mm seems like a lot, no?. What’s your criteria for replacement of the bearing?
November 19th, 2011 at 5:51 am
Hi Chris:
It is very tough to estimate the wear. The actual could be less. When the prop is lifted with some degree of force the total deflection is on the order of two or three mm (1/8″).At rest, you cannot see this much gap. If we were not pulling the drive line apart we’d not change these bearings for another 2000 hours. But since they are apart, and we have the spares, we’ll do it now as a preventative.
November 21st, 2011 at 9:19 am
Steve-
The line cutters need to be reassembled with a suitable Loctite Retaining Compound. Classic application for a machinery adhesive. This bonds the OD of the shaft to the ID of the non-threaded, cylindrical device. Much easier than knurling, keying, splining or the “wishful” set screw. Loctite 680 if it slips on, or 609 if it has to be pressed in place.
0.01 grams of prevention is better than 150 lbs of replacement shaft.
Best regards,
Mark Hoelscher