Whats the differance in a speedmaster#4 to a 3 and 3a?? Thanks Scott

A 4 is a shorty version of a 3. A 3A is stronger version of the 3 and handle more HP.

Is a 4 weaker then a 3a????

If it is a small shaft 4. A large shaft 4 is smilar to a 5. Alot of parts do not interchange however. 10x has #4's, maybe contact him.

As far as I know, the 4 is a shorty 3 and the 5 is shorty 3A. I didn't know they had different shafts for the 4's.

Based on that, the 4 is a little weaker. I think they are still rated about 700hp.

Also, the Speedy IV is 6" shorter than a III

Is there a way to know what shaft it has without opening the drive up???

A #5 will havea large prop shaft. Be careful because you can get a 4a with a large shaf also. If I remember there is a diffenence in lower case thickness for the beefed up shafts in the #5 stuff.

Small and big shaft size refer to the prop shaft. Props come in 2 sizes for the SSM.
Small shaft (SSM II, III, and some IV) are 19 spline. Big shaft (SSM IIIa, V, VI and some iVs) have 26 spline. The big shaft IV will be stronger.

what about the difference in length of a #II to a #III??