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Old 09-01-2016, 11:59 AM   #1
Senior Member
City: Hughesville, MD
Country: USA
Vessel Name: Branwen
Vessel Model: Hatteras 48 LRC
Join Date: Feb 2015
Posts: 315
Solution for shaft coupler bolts loosening?

Checking my shaft couplers was not a routine maintenance item, but a month ago I discovered that my starboard coupler bolts were so loose as to be ratthling around in their holes. Having never checked them in ~120 hours of operation, I couldn't say for sure they weren't always this way, but I didn't think they were. I tightened them as tight as I could, no idea the torque. I checked the port side, and all bolts were tight. I resolved to check the couplers before each outing, just as I'd check oil and coolant levels.

The couplers are held together with 4 large nut/bolt pairs with split lock washers between the nuts and the rim of the coupler. The couplers are solid metal with an alignment guide on one that slides into the center of the other that look like two hats bolted together along the brims when tightened down.

Subsequent checks of the couplers has shown that the starboard side requires retightening with as little as 10 hours running time. The port side remains tight. I can't see significant vibration at the couplers on either side when running, certainly no more on the starboard than on the port.

What should I do? Determine the required torque and ensure the bolts are tightened to spec? Any guidance on the appropriate torque? Continue to check and retighten as needed? Add some thread locker? If so, is blue good enough? Reconfigure the hardware to improve the locking mechanism? If so, what hardware would you recommend?

Thanks for your help.
GregBrannon is offline   Reply With Quote