470 vs alpha one

[spareparts]

ferm got it right on the Alpha year models. the upper unit between the two(Alpha and MR1 are simular, MC1 was the older units) didn't differ that much internally, they did differ cosmetically outside. ALl ALpha units also had the large trim cylinders, MR1 units had the odd skinny trim cylinders. the lower unit was where the difference was, the tapered drive shaft bearing was flipped over hte the lower gears were cut different to allow the gear load to push against hte upper bearing. The older MC1 lower units had a preload pin inthe top of the drive shaft that forced the shaft down against teh tapered roller bearing till the gears were under full load, pulling the bearing down, the Alpha(and MR1) didn't have the preload pin, the gears pushed apart against the tapered bearing(bearing installation was flipped). Just about any of the units are swappable, just keep in mind which trim cylinders you are using, and which ratoi you want to end up with. Some early alpha and MR1 units had an A stamped on the propshaft to designate it being an Alpha. Some early 80's 4 cylinder units looked like an Alpha on the outside(square top cap, large trim cylinders), but actually had the older MC1 style internals in the lower(look for the A stamped on the shaft). Alpha units were suposed to be 7 times stronger than the MC1 units. If you have any reason to replace the lower unit, I sugest you upgrade to an Alpha, it will bolt right on.

[aussie]

thanks guys again for the info

[moneyhole]

Stern Drive Engineering has a complete stern drive unit minus prop with a 3 yr warranty, they claim no matter if you hit a stump or fishing line, for the MR l (pre-Alpha) and the Alpha 1 for $1295. MR l & Alpha 1 use the same unit. That's the route I'm going... selling a couple of dirt bikes and an old Triumph 500 and I'm ordering that unit. I think they call it the SR106. Just need to know what ratio you want (1.62 for me) and it's on the delivery truck. I have talked to them a couple of times and they seem like very nice folks to deal with- very helpful and have all the answers to my questions so far.