Name this lower unit

**Dave S** · 02-01-2010, 06:20 PM

Sam the gears that are being made Could be expanded into SM and SSM gears as the tooling needed is there for the DS gear as the 75H prop has the same splines as the SM DriveShaft. Diff tapper.

**Mark75H** · 02-01-2010, 06:30 PM

At the cost of $700+ for the SM broach ... you gotta pay to play. As yet there is no interest in the SM gears

Both comments belong on another thread

**Dave S** · 02-01-2010, 08:01 PM

Read......SM the same as 75H Broach PS the splines on DS.

**Mark75H** · 02-01-2010, 08:33 PM

Not on the pinion shaft ... You of all people know the 75H driveshaft splines are the same as the Mk55H, not the SM

Its the prop shafts that are the same

**Dave S** · 02-01-2010, 08:40 PM

Me of all fools Know that they are buying a broach to do the splines of the 75H prop shaft.... the same as SM and SSM driveshaft.

Just giving ya a hard time.

It's winter and tired of shoving snow.

**smokin'joe** · 03-25-2010, 04:40 AM

This is not quite correct! In 1960 the regular OMC 75 had a high geared speedmaster-like shifting gearcase. They were faster than the Merc 800 with standard club foot, but not as fast as the Merc 800 with (2:3 geared) Sportsmaster gearcase. Anyone have a photo of the Sportsmaster? It was smaller than the 1975 OMC 75 'Nitro' gearcase used in EP/SE.
So 1960, from my experience in NOA, was the year that OMC reentered racing (also, don't forget Ralph Evinrude and Starflite I). I can tell you that, at the fall,1959 time trials at Three Rivers Boat Dock, there was nearly nothing present but a host of Johnson 75s on 13', 14' wooden Allisons. One upped the unlimited record to 56.5 mph, a speed unheard of at that time. It took us a year and the Sportsmaster gearcase for us to break 61 mph with the Merc 800 in NOA time trials.

Originally Posted by Mark75H

OMC made no racing equipment from 1941 until 1967. While Stephen Briggs controlled OMC this was the law. As Ralph Evinrude took over in the 60's things lightened up.

This lower unit is a Merc.

All of the older Merc Speedmasters and Super Speedmasters are 1:1, the 13:16 and 15:16 Super Speedmasters weren't made until the mid '70's.

If I tell Magic Float the 800 FGS didn't start until '61 and that it isn't exactly the right one, he will get it right by guessing the answer. The real answer is how you can tell it is that motor and not another similar motor made the same year.

OK can anyone tell me why it doesn't fit a 1963 1000 or a 1970 1350 and the rotation?

(Besides Magic Float and DaveS that is.)

**smokin'joe** · 03-25-2010, 04:48 AM

Strang may have promised it in 1956 but they sat on their royal butts while first Scott (1958-'59) and then OMC (1960) gave Mercury fits in NOA. Both had smaller, higher geared gearcases. My dad begged and begged Oshkosh for the Sportsmaster, complaining about the huge 2:1 club foot, and they finally sent us a Sportsmaster with two props, 17" and 19" pitch, in Aug., 1960. After that, we really took off. Probably, it was Kiekhaefer sitting on his royal butt. I don't know how many Sportsmasters were made. We and Paul Allison (a Johnson man in 1960) had one at the Oct., 1960 NOA time trials, and we put them to good use.

Originally Posted by Mark75H

Yes, Speedmaster equipped motors are normally run forward only.

Here is a little known fact:

When the first Mark75 was announced in 1956, Charlie Strang promised 3 lower unit variations: Standard "Fleetmaster", racing "Speedmaster" and an in between variation "Sportmaster".

The Fleetmaster promised speeds up to 60mph on tiny boats and the Speedmaster was promised for boats capable of over 80mph. For boats in the 60 to 80 mph range they intended to sell the Sportmaster.

The Sportmaster came in right and left hand rotation Dockbuster through prop exhaust versions. The water inlet was much like a Fleetmaster or Scott - - above and behind the prop. Unlike the Speedmaster it was marketed to be used with both long and short shaft motors. Rather than 4 different versions with 4 different driveshafts, the Sportmaster used a 2 piece driveshaft coupled just over the water pump. The gear ratio was 1.5:1 and the "R" dimension was 3.25 vs the Fleetmaster at 4.125 and the Speedmaster at 2.125.

The same 2 piece driveshaft arrangement had been used on preproduction prototype Speedmaster units labeled as test pieces for 80 hp motors.

The biggest surprise to me is the delay from announcement to sales of the Speedmaster and Sportmaster units. Maybe they thought boats weren't ready to go that fast. In any case, boats were never ready for the Sportmaster. They sold almost none and soon discontinued it. Maybe if it had looked like a giant Speedmaster it would have had better sales appeal.

**smokin'joe** · 03-25-2010, 04:50 AM

Yep, that's it! And I used one to break 61 mph in Oct., 1960. Paul allison, my dad and I were the first in (NOA) OPC to break 60 mph. All with that gearcase.

By the way-we ran it on the boat shown in my photo, the 13' Allison with two Mark 58As. I ran kneel-down with my butt against the transom. Boat ran up to 55 mph, lifted, and on the way to 61 mph shimmied like crazy-no bungee tie-down on the downhousing. I was 17, my dad wouldn't let me run the boat before the time trials!

Originally Posted by Mark75H

Quite unassuming. Easily mistaken for a 50hp lower unit.

Maybe Eric can supply a better picture...

**Mark75H** · 03-25-2010, 07:08 AM

The Sportmaster bullet is 3 1/4" ... I don't think it is smaller than the Nitro or the other cases:

http://forums.screamandfly.com/forum...d.php?t=210654

1960 OMC's may have briefly been competitive, but they were by no means fast, nor a "racing" case. OMC was still run by Briggs in the early '60's. Those boats & motors you mentioned were personally paid for by Ralph Evinrude outside of the factory ... Ralph was interested in racing, but as a company, OMC was not. OMC stayed out of racing until 1967

The Sportmaster gear ratio & bullet size were not legal in NOA in 1960 ... are you 100% certain about the year?

**smokin'joe** · 03-25-2010, 08:13 AM

I can tell you from personal experience that the 1960 OMC 75 would run. And, as soon as we got the Sportsmaster gearcase in Aug., 1960, it was approved by NOA (i.e., by Claude Fox). Mercury had sent them a bulletin stating the specs.

**smokin'joe** · 03-25-2010, 02:19 PM

Here's the standard 1960 OMC 75 gearcase. We had to run against that with a club foot before the Sportsmaster gearcase!

Originally Posted by Mark75H

The Sportmaster bullet is 3 1/4" ... I don't think it is smaller than the Nitro or the other cases:

http://forums.screamandfly.com/forum...d.php?t=210654

1960 OMC's may have briefly been competitive, but they were by no means fast, nor a "racing" case. OMC was still run by Briggs in the early '60's. Those boats & motors you mentioned were personally paid for by Ralph Evinrude outside of the factory ... Ralph was interested in racing, but as a company, OMC was not. OMC stayed out of racing until 1967

The Sportmaster gear ratio & bullet size were not legal in NOA in 1960 ... are you 100% certain about the year?

**Mark75H** · 03-25-2010, 03:52 PM

I remembered what that looked like. No one in my area could figure out how to get one over 35 mph. They must have been pretty tricky to get right.

Here's the copy of the ad from Hunn's book. I am clueless where it came from, I haven't come across it in any magazines I have from that time frame. Maybe its in an issue of NOA's Roostertails that I do not have, or maybe its a stock blank that was sent out to dealers for local use.

The WOA ad was a few years later and is in Yachting, Motorboating and others.

Like Joe says, WOA was a west coast/Arizona organization and NOA was heavier in the southeast ... NASCAR's old homeland.

**smokin'joe** · 03-25-2010, 04:42 PM

Are you confusing the 1960 75 with the 1958 Fat 50? The latter wouldn't do 35 mph unless you pulled it, the 75 would run nearly 50 mph on a Crosby-like runabout, was faster than a Mark 78.

Here's a picture of that disgraceful excuse of a motor. Same gearcase as the 1954 Johnson 25, just (like the rest of it) fatter.

Originally Posted by Mark75H

I remembered what that looked like. No one in my area could figure out how to get one over 35 mph. They must have been pretty tricky to get right.

Here's the copy of the ad from Hunn's book. I am clueless where it came from, I haven't come across it in any magazines I have from that time frame. Maybe its in an issue of NOA's Roostertails that I do not have, or maybe its a stock blank that was sent out to dealers for local use.

The WOA ad was a few years later and is in Yachting, Motorboating and others.

Like Joe says, WOA was a west coast/Arizona organization and NOA was heavier in the southeast ... NASCAR's old homeland.

**Mark75H** · 03-25-2010, 04:58 PM

No, there were practically no fat 50's in our area. I was always impressed by the looks of the 75's.

**smokin'joe** · 03-25-2010, 05:09 PM

Was easy to bust 50 mph with an OMC 75 on a fast boat, was pretty hard to do that with a Mark 78, and was impossible with a Scott 60 unless it was juiced up by someone who knew what he was doing-like McCulloch Corp.
And, the 52 mph 13' Rose was the fishing version, probably didn't weigh 150 lb. That was basically the same boat bottom that ran 50 mph with the Merc 500, after molded by Allison in 1961 (and the Merc 700 wasn't much faster).

Originally Posted by Mark75H

No, there were practically no fat 50's in our area. I was always impressed by the looks of the 75's.