What are the main differences between the #4 and #5 with big shafts. I know the original #4 had small shafts.

#5 is a much shorter drive - higher propshaft height.

I thought #4 and #5 length was the same. #3 was the longer version

4 and 5 are the same size, roughly 6" shorter tha a 3 or 3a. The 4's have smaller bearings and gears than a 5. Upgrade are available from Gary k.

Lil red is correct. All the #4's have a "polygon shape" front driveshaft, while some of the early #5's did also. In my opinion, the polygon shaft is just as "good" as the splined version that Mercury switched to in the later #5's. None, again from my sources, of the #4's had the near net forged, straight cut upper gear sets. They were a later "up-grade" in the #5's. The lower gear sets, RH and LH internal splines, on the #4's and the #5's are different with the #4's having fewer splines on the pinion gears, than the later #5's. A #4 can be upgraded to be, again in my opinion, as strong as a #5 with the addition of a set of the net forged, straight cut polygon'd upper gears and also the 1.75" dia. propshaft. I have both of these pieces, new, available for the #4. Check my classified ad for more information. If I can be of any help, please don't hesitate to give me a call.

Gary
612-247-7081

Ttt

its been said... Gary K has all the parts required to upgrade a #4 to almost what a #5 would be... the only difference would be that a #5 case is a little stronger, beefier in the bearing areas...

Alan is correct. I have new, near net forged, not machined, polygoned upper gears in a 1.31:1 ratio and new "big" 1.75" dia. propshafts all for the #4 SSM drive. Contact me if you need parts for your #4 or other SSM drives.

Gary
612-247-7081

Gary can i grab an email to contact re parts for ssmiv. Im located international.

I'm wondering about the power required to turn one of these drives. Would a small shaft #4 require less power (less parasitic power loss) to turn than a large shaft #5? Any thoughts?