I have a story to share with the hopes that a fellow club member might be able to relate and perhaps provide some insight:
I will start by stating that our boat is a 1986 Chris Craft Commander 336 express cruiser w/twin 454s.
This past summer we had an interesting, frustrating and costly experience when out of the blue, and without hitting anything, the starboard prop fell off of the boat, still attached to a foot and a half of prop shaft! Amazingly, we were able to retrieve the prop and partial shaft from off the bottom of the lake in about 5 feet of water. All I did was put the starboard engine into reverse at idle, (we were manuevering to anchor), and there was a faint clunk followed by loss of all propulsion on the starboard side. Long story short, we immediately dropped anchor, I took a look under the boat to discover a missing starboard prop, and we retraced our last steps using the tender until we floated over it and saw it on the bottom.
So, luckily it was a calm day on the lake and we limped on the port engine across the lake to our marine service location of choice. Turns out the starboard shaft had twisted off just past the cutlass bearing and down she went, prop and all! No real explanation was given as to why the shaft broke. We got a new one installed and also, upon being advised that the props could use a balancing too, got the props sent out to be tuned.
This is where it goes sideways. When we went to retrieve the repaired and ready to go boat and leave the marina, the boat was an absolute pig and would not plane out well despite the engine rpm's racing. Had to turn around and go back to get the tech. who ended up replacing the props with our spares after coming for a ride. Tried again and all was well, we were away. I left our freshly balanced primary props with the marina to try to figure out what was wrong. All were in agreement that something was not right with the props. A couple of weeks later, when I called them, they informed me that they had sent the props out to be rechecked, and the props were,in fact, fine after all. I said that was ridiculous since they were no good to me the way they were and they had worked perfectly fine before I had them sent out.
We ended up with a several thousand dollar bill, including something like $800 for repairs to our primary props and our unbalanced spare props were on the boat because the nice shiny main props were somehow junk! The spares are 16x14 and perform exactly as our primary props did before this all happened. The primary props are 17x17 as confirmed from survey and the prop shop has said that they are tuned exactly as they should be. I never actually took note of the prop particulars the day it happened, I knew they were Nibrells and according to the survey they were 17 by 17.
I am not a particularily happy customer. The tech, acknowledged that to run with the props would be bad for the motors, but I was told "you'll just have to sell the props on kijijji and buy new ones". My unpolished, unbalanced spare props are now my mains and I have no effective spares.
Anybody had a similar experience where they lost a shaft? Does anybody have a theory as to what the heck happened to my perfectly good props? Did they get swapped for somebody else's? Did they butcher them when they reworked them? Could they have been installed backwards? ( tech. said there was no way) and lastly, would you go through insurance to pay the repair bill and to try and get new props?
I can understand how 17x17 would feel sluggish if the 16x14 run well. Those are very different props. Is is possible that the pitch of the 17" was originally lower, like 17x14 and the prop shop brought them back up to what was stamped on them?
The survey would have only "confirmed" what was stamped on the props. As Steve said, if the props were original 17x17's pitched back to 17x14 but never re-stamped, then the prop shop could have brought them back to the 17x17 stamping. They should have scanned them before they re-worked them. Make some calls and find out if there is an initial scan available (before they did their work).
The first thing I don't understand is why there is a foot and a half of shaft sticking past the cutlass bearing. There should only be a couple of inches between the aft end of the strut and the forward edge of the prop. My brother had a 1980 silverton that the prop was 6 or 8 inches from the back of the strut and he had a twisted shaft break at 3000 rpms.
The other thing I don't understand is the if the pitch was increased then why were the engines racing. Increase in pitch would lower rpm's not increase them. Dave