Hi all,

I'm venturing out on my own here after eyeballing several designs, including the mad mud motor plans.
My neighbor who used to race hydro boats professionally, gave me a stainless prop shaft that measures 8', and is 1 1/8" O.D.

I want to fabricate a long tail outdrive that uses two pillow block bearing housings, and leaves the prop shaft exposed. On the PTO end, it will have the traditional U-joint coupling that most manufactures use, then aft of the U joint will be the first pillow block. About 4 feet down from that will be another pillow block, and both will be bolted down to 3/4" square stock (hollow) that run parallel. Neither one of these pillow block bearings will be submerged, but I'm having problems figuring out what bearing/bushing should be used at the prop end (the portion of the shaft closest to the cavitation plate, just forward of the prop)

The same guy that gave me the hydro prop shaft told me about a bushing that they use on the race boats, where the prop shaft rides underwater. He says the bushing that they use is lubricated by water, but doesn't know what its made out of. He seems to think that it is made out of phanolic (spelling?) or carbon fiber.

I was intending for this last bearing housing to be the structure that the skag and the cavitation plate bolt up to. I'm gonna need something that is either lubricated by water only, or perhaps a traditional brass bushing that has seals on both ends?

If I was a little more computer savvy, I could draw out the plan, but its really simple. Picture two sections of 3/4 square stock that are parallel to each other, and 8 foot long. the two pillow block bearings bolt to the center and to the U-joint side, but the prop side is the one I'm having problems with.
Maybe just run 3 pillow block bearings, and keep the one under water greased with water proof grease?
Any ideas would be greatly appreciated. Or make fun of it too if you'd like!

Most designs use a closed housing because you can insert a bronze bushing in the bottom end that is submerged, these bushings are lubed with grease inside the housing. I would suggest some kind of shaft housing just for safety sakes and it makes the design much simpler. We use a roller bearing at the top of the shaft if that helps, but a bronze bushing at the bottom is pretty rock solid, or fab a cone to fit another roller bearing in the bottom for less resistance. Also give back or scrap the racing boat prop, standard boat props don't work for these motors because the engine spins the wrong direction, also if you wreck this prop at some point you'll have a crappy time finding another prop to fit the shaft size (3/4"), and the pitch/size will be a challenge to match up for good performance. Im definitely not a pro, and not trying to make fun of your design! but I've put together quite a few longtails and this is what I've found... If you got some more questions feel free to PM me!

Well said above, I have built around 6 LT now and bronZe bushing are by far easiest, but I like the tapered roller bearing the best, just a bit a time to make a housings

cutlass

Thanks ya' ll for writting back,

The reason I wanted to steer clear of the traditional prop shaft/housing design is because it sounds to be too much time/effort devoted to trying to find bushings that are the correct O.D. to fit into the shaft housing I.D. Then you gotta haggle with the bushing I.D. being tight enough to allow the shaft to run through.
I really don't want to have to pay a machine shop $ to turn down ANYTHING on a lathe to get it to fit snug. Then there's the problem of vibration. Its similar to a weedeater shaft .spinning inside the housing. After a while, the bushings will wear to the point where the shaft vibrates- cause its not spinning true.

My design using the pillow block bearing truss' mounted on the square stock seems in theory to be of a much simplier design. The only downfall to the design that I see is its gonna be heavier. Hopefully not by much.
My neighbor gave me a prop drive shaft, not the prop itself, and one thing I like is the shaft is balanced, and its true. Rust wont be an issue, cause its stainless. If the pillow blocks stay greased, they wont ever wear out. Unlike the U joint or brass bushings.
Im still interested in hearing about the tapered roller bearing ya'll are talking about- is it on the U joint side? Also, what bearing can be submerged, and sealed on both sides?