how can you tell the difference from the early III and the later IIIa's
thanks
later

IIIAs have the larger 26 spline prop shaft. Uses the same props as SSM V and VI. IIIs have the smaller 19 spline 1 3/8" shaft.
There are also some differences in the gimbals in the later IIIAs to make them stronger.
Gary

what year did the IIIa's start being produced?
later

You can't tell by just the prop shaft, as it is possible to put the shaft from a big shaft #4 in a 3.

Take a look at the tilt pin hole, a 3 is 3/4, a 3A is 1". Of course it is possible to drill that out too.

I guess I'll be more careful the next time I buy a IIIA from BAM

Marc, Will a 3a or 4 lower bolt right up to a #3?If not what do you need to do to convert them? Thank's, Ike.

Marc, also what drive oil do you recommend for my #3's? Ike.

Ike, no way to convert. A 4 upper is a different housing. A 3 and 3A have different vertical shafts in the lower.

We us the good old Merc HP gear lube.

What are the differences between a 3a and a 5 other than length?

I've got 5's on a boatwith stellings boxes we're riggin and we're just now dialin in the props. Maybe a cupped prop will help us get on plane faster.

Its a 38 that weighs 7800lbs. The drives are right below the transom, We're gonna try some cupped props next week to get that thing to plane off.