speedmaster / sportmaster....gear foot

[switzerbullet]

:confused: Can someone give me a little history on them? I know speedmaster was the early foot, but what are the differances? What years were they made? What styles? #4? #5? Gear ratios? Remote pickup? What fits the early 70's Merc 150?

[Mark75H]

When the first Merc 6 cylinder motor was introduced in 1956, Merc's chief engineer promised that there would eventually be 2 special high speed lower units for them. The stock lower units were very good up into the low 50 mph range. One of the special lower units would be for boats that could run in the 50 to 80 mph range and the second special lower unit would be for boats that could run more than 80 mph. Merc was already making racing lower units for their very popular (and now famous) 2 and 4 cylinder racing motors that were running up to about 75 mph on small racing boats, but these were not really big enough for the 6 cylinder motors.

Two years went by and Kiekhaefer turned away from producing the special lower units for the 6's for sale to racers. Instead a side project came up that called for a special lower unit under a special super short mid section for a world speed record attempt. A lot of testing at Lake X lead to the Merc Mark 75H which raised the speed record to 107 mph in 1958, a full 7% increase over the previous record held by a one off special outboard motor based on a car motor. A very limited number of Mark 75H motors with 1:1 gear ratio units were sold, probably 50, in addition to the 50 or so prototype pieces made before actual production.

Three more years went by and Kiekhaefer got wind of Scott McCulloch prepairing to introduce a racing lower unit for their 3 cylinder 60 hp motor. At about the same time Scott got their racing stuff to market in 1961, Mercury released the 2 special racing lower units they had promised 5 years earlier in 1956.

Right off the bat in 1961 Merc released 2 versions of the 1.5:1 Sportmaster and 4 versions of the 1:1 gear ratio Speedmaster to fit the 1961 Direct Reverse mid sections. The Sportmaster came in right and left hand rotation with a 2 piece drive shaft to accomdate the 2 different crankshaft spline sizes in the 70 and 80 hp motors. Speedmasters came with full length driveshafts for either the 70 hp crank spline or 80 hp crank spline, both types in right hand and left hand rotation. In general the internal works and hydrodynamics of the first version Speedmaster was directly derived from the bottom end of the Mark 75 H lower unit, but altered to fit directly on the bottom of the Merc 700 & 800 midsection. Water inlet is at the bottom front of the nose. Before the end of 1961 a heavy duty version of the 80 hp type came out with stronger bearings in the upper driveshaft bearing position. With the introduction of the 100 hp six in 1962 an improved version of the Speedmaster was released with a slightly different housing and different water inlet position; top bolt flange now set up to fit the gear shift type mid section bolt pattern used thru the end of inline 6 production.

The Sportmaster was not a commercial success, because in 1961 there were very few boats that ran between 50 and 80 mph. You either had a pleasure boat that went something under 50 mph or a raceboat that went well over 75 mph; only a very few boat racers used them with success. Cosmetically a 1961 Sportmaster looks very much like a Merc 450 or 500 fishing lower unit. Almost all of them were set aside and lost or mistakenly trashed as unused 50 hp units. Water inlet is the same place as fishing Mercs and many other brands of the 1960 era, from prop spray into an inlet on the bottom of the cav plate.

By 1964 racers were really punishing the Speedmasters in marathon racing under the 100hp stock motors and 110-115+ hp modified motors. Some races were won by fast pit changes of worn out Speedmasters getting back on the course before the other guy changed out his busted lower unit and got out. Merc's answer to this was the "Super Speedmaster" introduced in 1965. Again the gear ratio was 1:1 and forward only ... no neutral or reverse. The Super version also came in right and left hand rotations. The Super Speedmaster was stronger than the regular Speedmaster because it had 2 driveshafts one behind the other turning opposite directions driving 2 gears on the prop shaft. Equal loading (more or less) of the gear pairs was acheived by making the lower driveshaft sections very thin. So thin that they flexed. The Super Speedmaster prop shaft was also supported by more bearings as were the dual driveshafts.

Super Speedmasters (SSM's) were sufficient until hp approached 150. At 150 hp right hand SSM's were still up to par, but left hand SSM's could not take the load. Merc's solution for boats running 2 motors wanting one RH rotation prop and one LH rotation prop was to run one motor backwards and make a few minor changes to a RH SSM to allow it to work with CCW input and output. A second tier solution was to use the first MerCruiser sterndrive Super Speedmaster which had turned out to be a little weak for sterndrive use. This SSM was called a MC-1 SSM for "MerCruiser type 1 Super Speedmaster"

The first V-6 racers used the same SSM's as the inline 6's. The only significant change was the introduction of an optional 14:15 (reduction) gear ratio instead of the previous 14:14 ratio. As power dramatically increased with the V-6's 2 larger heavier SSM's were introduced: the VI and the IV (6 and 4). The 6 is larger than an inline SSM, but slim and trim compared to a big fat type 4. The VI and IV only bolt up to the special racing mid section, no longer an accessory fit to the std mid.

As far as putting one on your 150 the ideal one to find and use is a RH SSM or MC-1 SSM.
A few words of caution:
(1)start in gear forward only is a big fat pain in the butt
(2) props for all Speedmasters start at 15 inches of pitch and go up into the 20's. These are the equivalent of 30 to 42+ inches of pitch at the 150's std 2:1 gear ratio. If your boat isn't already running 80 or so, plan on spending $600 or more for a custom made prop to use a SSM at lower speeds
(3) SSM gears and bearings are tiny, wear is instant and continual. Change your gear lube EVERY time you use the SSM
(4) exercise caution buying a used SSM. You are probably buying a used up piece that needs $1000 worth of rebuild
(5) don't expect much if any speed increase on a rig over 550 pounds with driver. SSM's were just not made for this use

[Mark75H]

I added the images above. #1 is obviously the Sportmaster. #2 is the 1961 Speedmaster (arrow points to the water inlet on the housing instead of nose cone). Bottom diagram image is from the Super Speedmaster patent showing the thinned down driveshafts one behind the other.

Key differences:

Sportmaster 1.5:1 gear ratio, thru prop exhaust, 3 1/4 bullet diameter, cav plate water inlet

Speedmaster 1:1 gear ratio, 3/4" shaft with 5/16" shear pin, 2 1/8 bullet diameter, water inlet below bullet

Super Speedmaster dual internal driveshafts, 1:1 gear ratio early, 14:15 and very rare 13:16 options later, 12 spline prop shaft, 2 1/8 bullet diameter, water inlet below bullet

VI 14:15, 15 spline? only fit the V-6 racing type mid section

[switzerbullet]

Thanks Sam
Thats a great help! We can always count on you for detailed answers.

[Mark75H]

Thanks Sam
Thats a great help! We can always count on you for detailed answers.
Or excessively long boring monologs, I don't know which:confused:

Oh, one thing I omitted ... I intended to thank 2 guys that really educated me on these: Norris Wallace (Raceman) and Dave Schwarz (Dave S). I knew some about Speedmasters before I met them, but not as much as we all know now.

[rostertails]

Just what I am looking for, any out there for sale? :)

[switzerbullet]

The boat might be a little heavy (unless I stay out of it!). I just found the Merc 150 with the 125 cowling on it. The guys boat was rated for 125 H.P. hence the 125 cover. I thought that if its going to ride like a washboard and turn like a skipping stone, I might look for a super speedmaster to get it as fast as I can. I also found a couple nice 2 blade props on ebay that I think will work (I need to check how many splines).

[Dave S.]

Those props look like early 150XS props with the rubber hubs. Just like BP props but more Dia and rubber hubs. I like the Kg9 in the back.:) The boat is cool too. I would try a 24-26 pitch chopper jacked high on that boat and skip the speedmasters.

[Mark75H]

I think Dave is right on the props, BP/std LU

[Sunburnt]

Thanks for the Great History lesson again Sam..

God, I just love that stuff... :cool:

Work will resume on my Powercat shortly, Maiden Voyage is tentatively scheduled for New years Eve.. The first Annual Dicksmarine Regatta held at Saguaro Lake AZ.:D

Jeff

[Pvp350rz]

I have a Super Speedmaster Lower unit Left Hand rotation (972LH) about 1965 built. The waterpump faceplate is for only one crank rotation direction as it has just one discharge piecut. The way it fits on the lower unit puts the discharge piecut on the port side. Is this correct for a right hand looking at the flywheel (normal rotation) engine?