What's This??? - 727 ?? vs CCC Gearcase

[RogerH]

Here's two pictures that show the differences of two OMC gearcases. An original CCC gearcase is on the right and has an original length stubshaft installed and a longer one beside. Needed the longer stubshaft to use this GC with a 235hp block that has a stock crank - not the damper crank.

It turns out that the GC on the left has a 14-3/8" driveshaft - the same length as my CCC GC with the longer stub-shaft. The original CCC driveshaft length is 13-1/8". (Measured from top of gearcase housing to top of driveshaft)

**** Waterpump base on left is P/N 727D1110 Waterpump base on right (CCC) is P/N 322358 ****

Lots of things are different
- long vs short hub prop shaft
- slightly larger / different water pump
- Fill / drain holes located higher
- Casting is generally heftier - cavitation plate thicker
- No P/N cast into the Left gearcase housing
- shorter skeg
- 10 studs vs 8 studs for mounting
- Haven't checked gear ratio yet - 15:17?
- Bulge in case just below cavitation plate. Reinforced stud area to right of fill holes
- profile different between cav. plate and prop-shaft

[Powerabout]

Whats with the 2 pipe cooling system?
( I have never played with a ccc)
Merry Chrsitmas Roger
Regards

Powerabout

[RogerH]

Whats with the 2 pipe cooling system?
( I have never played with a ccc)
Merry Chrsitmas Roger
Regards

Powerabout

Powerabout, I'd like to know the answer to that too. Note that the one I've been using has a plug in one side. The two openings open into the same cavity of the pump base, so I haven't a clue why there are two. Maybe that pump was used in another application that required the opening in another location?????

[Powerabout]

Hi Roger

I can guess that it was designed before the V6 consumer engine came out therefore they used V4 stuff which was a 2 pipe system back then.
I guess if we looked at the dates it might make sense but I dont know when the ccc was released.

[RogerH]

New Discovery - The gear ratio is different
CCC/RS = 15:17 per documentation (88.2%)
Mystery GC = 8:9 or 16:18 (88.88%)

I thought I messed up the first time, so checked it again today. It is definitely 8:9 (8 prop shaft : 9 drive shaft)
The top two gears are engraved "89", haven't been inside yet.

Additionally, Mark Poole noticed in the 1979 Havasu World Outboard Championship You-Tube video that at 2:34 minutes they show them taking a gearcase off Ken Stevenson's Johnson RS, and you can see the bulge under the cav. plate. No idea what motor really is under the RS cover.

[RogerH]

Confirmation on 727 Gear Case received today:

The gearcase is a late style 727. The part number referenced 727D1110 is the part number for the bearing cover, the gearcase was 727E1111. The 727 gearcase was designed to allow gear ratio changes using a set of change gears at the top. We had 14:17, 15:17, 16:17 and 17:17 sets. The gear set pinion/bull gear were 16:18. The first parts were completed in February 1978. The propshaft length was changed (+3/8") in May 1979 to allow differrent design props to be used. In addition to the standard gear sets we made a 1:1 set and an Overdrive set. After lots of testing we settled on the .88 ratio as the best all around.
The midsection was new to allow for a larger blow down area thus the addition of the extra mounting studs. As you know the engine was an even fire engine which started out at 173ci and was increased to 183ci. First raced at Havasu where they all broke. We later found the problem and it became a great race engine.