Propeller Repair
On August 2, a warm Saturday afternoon, Laura, Gordon and I went for a leisurely ride up the Kanawha. We'd gone past Saint Albans and were in the Institute area when we decided to turn back because the weather was looking threatening. It turned out it wasn't just threatening, it meant business. Between Saint Albans and Nitro, we ran into a downpour. I put the covers up and we stayed relatively dry but couldn't make much headway for lack of visibility. The rain stopped after a little while and we decided to high-tail it home since it looked like there was more where that came from.
I'd only been on plane for a short time when, just as we passed under the I-64 bridge in Nitro, the boat lurched and simultaneously the engine RPMs surged. Sensing that something was happening that shouldn't be, I throttled back. After we stopped I shut down the engine, went to the back of the boat, and looked stupidly at the drive unit. It was still there.
I
raised the drive so I could see more of it and leaned out and gave the prop a
little turn. Everything looked and felt normal, so I put the drive back down and
refired the engine. I put it in gear and tentatively advanced the throttle.
Again it seemed normal, so I tried to speed up again. At about 3000 RPM I again
got the increase in RPM with no corresponding increase in acceleration. I tried
this a few more times with the same result.
I'd read about spun hubs in rec.boats and my symptom appeared to point in that direction. Old Mercruiser propellers like mine have a rubber piece that's pressed into the propeller to isolate it from the drive shaft somewhat and to reduce the amount of shock that's transmitted into the drive unit. Some newer propellers have an isolator that can be replaced with common hand tools, but mine has to be done with a press and some special holding fixtures.
Since we were just a little way upstream from the Poca ramp, I called Charlie and asked him to meet us there. We continued at low speed and arrived about the same time he did. Gordon and I rode home with Charlie to get the trailer and Laura stayed with the boat tied up to the dock about fifty yards downstream from the ramp. (The little dock next to the ramp has been unusable since the winter floods.)
When I got back with the trailer, I saw that the ramp was available and motioned down to Laura with the universal man-sign for "meet me over there." Apparently the universal woman-sign for that is something else, because she didn't understand. With my car parked in the center of the ramp and trailer in the water, I climbed up onto the hill where she could see me and again made a come here gesture. Apparently she partially understood what I meant and got out of the boat and started up the hill toward the road, half crying and all cursing because she didn't have any shoes and the ground was rough. I started toward her shouting, "I meant bring the boat," but by this time I was nearly there and decided to do it myself.
After getting the boat going, I approached the ramp and saw another boat lined up as if he was going to put his boat on my trailer. Then I saw some guy on the ramp in a pickup trying (unsuccessfully) to jockey his trailer past my car. Admittedly I'd been there a bit longer than necessary, but this guy obviously had no patience and, coincidentally, mine was wearing a little thin. (We were the only two boaters there.) I headed straight for the other boat, glaring my sternest glare, and the guy in it got the idea and moved out of the way. Pickup guy saw what was happening and had the sense to pull up to the top of the ramp and wait. I loaded my boat on its trailer and pulled up to the parking area to secure it, glaring also at the pickup driver as I passed him.
I took my prop off on Sunday and couldn't see any visible signs of the problem, although I understand that's typical. I took it to WV Marine on Monday so it would be there in time to catch the Tuesday truck to the repair shop. I asked about other possible causes while I was there and was told that about the only other part likely to produce my symptom would be the engine coupler, but those typically produce a tell-tale odor when they go bad.
My prop
arrived back on August 12, right on schedule. I noticed when I picked it up that
the hub looked different. The inner part appeared to be pressed farther into the
outer hub than before. Prior to having the repair, I could place the thrust
washer on the front of the hub and its inner boss would contact the inner hub.
When I got home, I tried this with the newly rebuilt hub and found that the
outer boss of the thrust washer contacted the outer hub before the inner one
contacted the inner hub. a quick measurement confirmed that the new inner was at
least a sixteenth of an inch farther toward the rear than the old one.
I called WV Marine from work the next day and asked if this was normal. I was told that it's possible that when my old hub slipped it moved in the fore and aft direction. I was also assured that the hub repair company that WV Marine uses, Blackburn Marine Distributing of Friedens, Pennsylvania, knows what they're doing and that if there was any problem at all, they'd make it right. (I wasn't really suggesting that the job wasn't done right, I just wanted some reassurance that what I was seeing was normal since I have no frame of reference, this being the only boat propeller that I've ever had any personal contact with.)
I put the prop back on when I got home that evening and noticed that, after tightening down the prop nut, the front of the prop was noticeably closer to the back of the drive unit than before. I also noticed some signs of slippage that I'd missed before: the front of the splined washer that goes ahead of the prop nut had some rotary score marks on it.
The following Saturday I launched again and tentatively tried out the repaired prop. It went through 3000 RPM and beyond with no signs of trouble. On the way home I asked Laura if she thought the boat's sound was different and she confirmed that it was. There also seemed to be a little less vibration and the left turning tendency was gone. I was relieved that my diagnosis was correct. We were back in business.
On Sunday morning, August 24th, we saw this cruise-barge going up the Kanawha towards Charleston:
