LOL! Yeah, I forgot he was talking about an outboard. Still, I'd use a flexible coupling in that application, too. Just torquing the motor bolts could put undue stress on the bearings. If the shaft was unsupported at the upper end, you might get away with no flex coupler since the flexing of the shaft itself would take care of a lot of radial flex. However, by eliminating the spline connection, you lose axial movement. Differential expansion and contraction of the aluminum outboard motor lower end and the steel shaft could put some load on the bearings, reducing their lifespan. I have three $3000 vacuum pumps at work. All are C-mount and short-coupled between motor and pump, and they all have a flex connection between them. Never had a bearing or pump seal problem and they have run 8 hours a day for over 8 years. Or, to put it a better way, a lovejoy connector is a lot less expensive than a set of motor bearings, let along the inconvenience of being stranded on the water, or the time it takes to change out bearings.
--- In electricboats@
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> ????
> I am totally puzzled for two reasons;
> 1. I have been the owner of many of the millions of boats with the prop shaft hard connected to the motor. 0.0005 per inch of coupling face is the standard alignment spec. This is the same spec for aligning electric motors in industrial applications. Lovejoy and other couplings are for low hp applications and to minimize shock load. You line up a LoveJoy exactly the same way, before installing the rubber cross.
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> 2. This is an OUTBOARD MOTOR the fellow is connecting to so what does the flex of the hull have to do with the coupling?
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> --- In electricboats@
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> > Myles, The "guarantee" is the splendid bit of engineering you do that calculated the shear values. The fellow wanted to avoid welding and machining, which is why I came up with this solution.
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> > When I said "buy a coupler" I meant one of the many types that allow movement and misalignment like a Lovejoy connector. Prop shafts should never be hard connected to motors, especially in boats because the boat itself can flex, causing excessive force on the motor bearings.
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