Coupling between engine and prop shaft

[Bill CD28 Kittiwake]

Today when I started up the MD7A, it sounded good in neutral, but promptly got some clunking and shakes in reverse. Turned off the engine, looked below at the coupling between engine and prop shaft, and started her up again. Same thing, except this time I saw that the coupling was missing 3 of the 5 bolts (hex-type) that held the coupling together. Found the remaining 3 bolts in the bilge and fished them out with magnetized expanding "pointer). After cleaning them off - they were in good shape, and all were snugged back in.

Question - does anyone know if there is a torque for these 5 bolts, or have any suggestions as to why they came out? Have put about 100 hr on engine this summer, nothing to suggest problem until today.

I then noticed that I had a steady drip coming in along the shaft. Bilge pump is cycling on and off, pumping out about 5 strokes of the small bilge pump every 10 min. After tightening the bolts and restarting the engine, did not see any apparent vibration in the shaft.

Question - What, if anything, would you expect to have been damaged or loosened because of the coupling being loose?

Thanks - Peace and Fair Winds, Bill Watson - CD28 Kittiwake

[Parfait's Provider]

Seems that if there was enough vibration to be noticed as you indicate. the flax in the stuffing box would have been pounded out of shape at a minimum. If it vibrated for many hours there might also be wear on the shaft which will make it difficult to impossible to adjust the stuffing box properly. However, that is the first thing I would try.

First step is to see if the drip will go away with a slight tightening of the packing nut. This can be confusing; the lock nut (nearest the stern) needs to be turned away from the stuffing box, the packing nut turned toward the lock nut, and then the lock nut towards the packing nut. With right-hand threads, which the Spartan box has, and facing aft: turn the lock nut clockwise, the packing nut clockwise, and then the locknut counter-clockwise. There are special wrenches for this, but a large screwdriver and hammer work.

How tight? Well, some would say it ought to be dry when the shaft if stationary and drip slightly when the shaft is turning. The objectives are to minimize dripping while not overheating the flax and damaging the shaft. Best thing to do is to tighten it so the dripping stops, run the boat for awhile, checking for drips, then shut it off and touch carefully. The stuffing box should only be warm, not hot.

Good luck.

[Kittiwake]

Thanks - have tightened the packing nut - stuffing seems to be okay. The drip has gone away. Am going to run in some and watch for leaks and check the temperature as you describe. Will also do a lunch hang tomorrow to clean the bottom and check out the running gear.

Thanks for the great description of how to evaluate it and tighten it up...

Peace and Fair Winds, Bill

[wayne grenier]

You need to put locktight on those bolts-not only will it prevent them from backing out again-it will make it easier to remove them in the future if you need to-usually they rust up and need to be soaked with WD-40 before removal-the same thing happened to me-

[Kittiwake CD 28]

Wayne
The boatyard also discussed using Loktight with me. No question that it will help. The hex bolts weren't as rusted as I thought, but still soaked them in WD40 for awhile before reinstallation. The Loktight is a project for today or tomorrow, after running it for an hour or so.
Thanks, Bill

[Ed Norton]

Bill
I would recommend castle nuts for this application. These nuts are matched up with bolts that have a hole in the end. When nuts are secure you insert ss aircraft wire through nut and bolt and twist to secure. This prevents the nuts from coming loose. Lock Tite works but it's a bear if you ever want to take the nuts off. With the castle nut system you simply cut wire and remove nuts. This system is used extensivly in the aircraft industry.
Ed Norton

[Parfait's Provider]

Loctite comes in colors; you probably don't want a permanent loctite that requires heat for disassembly. Try Loctite® Threadlocker Blue, not Red. See: http://www.loctiteproducts.com/products ... 8&plid=153

Also, WD-40 is a solvent, so you need to put something on those threads whether it is Locktite or something else. I like the idea of castelated nuts, but I would think they might be more expensive than Loctite or even Nylock nuts which don't need a bolt with a hole in the right place; Nylocks are another product used extensively by the aircraft industry and readily found in stainless.

[Guest]

Thanks for the replies. I ended up starting with Blue Loktite. Kittiwake was pulled out for a lunch hang yesterday. Cleaned the bottom (almost spotless - the Trinidad SR has paid for itself - Back Creek known for its growth) and went over the running gear. Everything in good shape.
Did discuss wiring the bolts last night with folks from the Navy Shipyard here in Annapolis. That will be the next approach, along with regular checks. I'm getting better at emptying the port locker and sliding down in.
Tomorrow the journey will begin. Will post a blog site once I get going.
Peace and Fair Winds, Bill