SSSM driveshaft question for old inlines.

**Tom Smyth** · 05-15-2017, 12:12 PM

So I guess I have never understood the reason why some of the SSM on inline motors had a full length one piece driveshaft while others utilize a lower stub driveshaft with a intermediate one. I guess this was kind of common on the SBP lower units but can someone explain the reason why ?

**GENE LANHAM** · 05-15-2017, 12:33 PM

Originally Posted by Tom Smyth

So I guess I have never understood the reason why some of the SSM on inline motors had a full length one piece driveshaft while others utilize a lower stub driveshaft with a intermediate one. I guess this was kind of common on the SBP lower units but can someone explain the reason why ?

Tom--the SBP on the Offshore boats came with two different lengths--Maybe it was easier to inventory two driveshaft lengths than to inventory two different Lower Units?

The original BP driveshaft was a two piece/rubber coupled affair that had a service life of about 60 minutes--

**bernie** · 05-15-2017, 12:47 PM

Stub shaft SSM - maybe for MerCruiser use?

**2us70** · 05-15-2017, 03:11 PM

Looks to me that the stub shaft unit would be easier to change in a hurry. I recall guys pitting for lower unit failures in some of the longer endurance races. In the 9 hour you had to already have it in the boat and change it with tools also on board without outside assistance.

**Tom Smyth** · 05-15-2017, 03:34 PM

I wuz thinkin that the two piece driveshaft would allow for a rubber coupler to maybe help absorb the shock of shifting on the SBP lower? I don't see how it would increase time to change lowers as you still would have to insert and hold the intermediate driveshaft somehow. Seems like a once piece would be easier and quicker.

**Tom Smyth** · 05-15-2017, 03:35 PM

Originally Posted by GENE LANHAM

Tom--the SBP on the Offshore boats came with two different lengths--Maybe it was easier to inventory two driveshaft lengths than to inventory two different Lower Units?

The original BP driveshaft was a two piece/rubber coupled affair that had a service life of about 60 minutes--

Good point Gene.

**milkdud** · 05-16-2017, 09:56 AM

Yep the BP had two different mid lengths like Gene mentioned.

I see lots of SSM's with mid shafts. I think when the T2X came out with its shorter mid section length lots of 15 inch SSM's got chopped and used an intermediate shaft.

Using an intermediate shaft would let you put the lower unit on more than one motor without taking the driveshaft out and messing with gear set up which is a huge pain.

You could have a T2X mid shaft and a STD 15 in MID shaft for a SSM and run that lower unit on various applications very easy without much time involved.

I don't think Merc ever used a mid-shaft for the SSM's. It was racers doing so.

**Tom Smyth** · 05-16-2017, 10:41 AM

T2X when it came out had a unique length single piece driveshaft from the factory to go along with its 12 inch mid length.

Likewise the MC-1 driveshaft ( single piece) that came out before the original Twisters were an inch shorter than a standard 15 inch which the SSM used. These motors require the hard to find shorter adapter housing if you want to run them on a standard BP mid or fishing motor 15 inch mid.

Or you need a good bolt stretcher to use on the driveshaft.

you can see from this chart that the XS and T2 basically use the same standard length driveshaft. Everyone else came from a different planet I guess. EK must have had his reasons.......

Notice no mention of the standard SSM or the BP 's.

**FUJIMO** · 05-16-2017, 01:57 PM

Originally Posted by Tom Smyth

So I guess I have never understood the reason why some of the SSM on inline motors had a full length one piece driveshaft while others utilize a lower stub driveshaft with a intermediate one. I guess this was kind of common on the SBP lower units but can someone explain the reason why ?

The Speedmasters went on engines that were, most commonly, just one midsection length. Beginning in 1968 many different inline midsection length outboards became available in racing. (Simular to all the power & transmission options that suddenly became available then, for musclecars.) When the consumer 3.0 litre Mercury V-6 came to market in the 90's, the gearcases were immediately available with stubshafts and all different one-piece shafts. The need was there. All the large Mercury's since, Verado's included, are produced with the various shafts. The need is there. With the oldest Speedmaster's, there just wasn't any need.

**milkdud** · 05-16-2017, 01:58 PM

I didn't know the MC-1 would not work on a 15 inch mid? I almost bought one once to run under a 1500 short shaft. I guess it would not work? With that in mind, if I put the SSM adaptor on my SBP down the road will my normal 15 inch SSM's be too long? All stuff I have not got a chance to do yet.

**FUJIMO** · 05-16-2017, 02:08 PM

Originally Posted by milkdud

I didn't know the MC-1 would not work on a 15 inch mid? I almost bought one once to run under a 1500 short shaft. I guess it would not work? With that in mind, if I put the SSM adaptor on my SBP down the road will my normal 15 inch SSM's be too long? All stuff I have not got a chance to do yet.

If memory serves, there was two or three different driveshafts available for the MC-1. Finding an original one today would be futile. Anything can be made, for a price.

**Tom Smyth** · 05-16-2017, 02:38 PM

yes I haven't had to take my MC-1 apart so I cant say how close it is or isn't to other SSM driveshafts or even a standard driveshaft. have it on pretty good authority though that they were standard on the first Twister 1 Motor s in 1970. Cant speak to the length since the Twister 1 did use a BP mid but no clue about the thickness of the adapter used also.