Flex type coupling or u-joint?????

[Tygafan]

I am building a 45' Bruce Roberts Waverunner and have 2 x 150 hp diesel engines with gearboxes that will need to be coupled to the prop shafts. What would be the best method for coupling the shafts to the gearboxes to deal with torque, torsional vibration, minor misalignment?

[brian eiland]

Have a look at this Thompson Coupling

U-joint, CV- joint, Thompson coupling
U-joint, CV-joint, Thompson coupling

[Brent Swain]

I had a U joint on my last diesel, a ten HP aircooled. It worked well. I heard about a guy who had two on a short shaft in a wooden hull. When the one on the propshaft broke the short intermediate shaft became a flail and flailed a huge hole on the hull . CV joints are less likely to break.. In a steel hull you are unlikely to punch a hole , but in any other materials, a piece of steel under and over it may be a good idea. In a steel hull, if you use two u joints ,a piece of steel over it is a good idea.
Brent

[kengrome]

Lovejoy couplings are good, cheap, and won't flail if they break. They take up shock well, and they handle slight misalignment with no problem. They also make it faster and easier to separate the coupled components than any other coupling I'm aware of.

[Tygafan]

Thanks for the great responses. I am looking for an economical yet effective means of coupling my prop shafts to the gearboxes. I don't mind dropping a few dimes for quality but I don't need some kind of NASA device at NASA prices either. Has anyone here ever used a Dodge coupling to couple a prop shaft to a gearbox? I am open to all suggestions.