OMC 727 race motor

[Powerabout]

Any updates Greg?

[RogerH]

Just catching up with this thread. A while back I cam into the possession of what I thought was a CCC gearcase. The first clue was when I saw the water pump casting number had 727 on it. The 2nd clue was when it wouldn't bolt up to the CCC midsection. Upon close inspection I could find 10-12 diferences, but they wren't obvious at first. Take a look at the side by side pictures of a CCC GC and the 727 GC. The CCC GC has the 2-piece shaft. Greg now has this unit.

Well I can't add the photos????

[Ron Hill]

Ronhill@hillmarine.com and I'll try and post them.

[RogerH]

Ronhill@hillmarine.com and I'll try and post them.

Ron, I'll try again this morning and send them via email if I am unsucessful - Thanks Roger

[RogerH]

727 vs CCC: A couple of things that aren't too obvious from the photos: There is an extra pair of mounting studs. The water pump housing is a bit wider and
contacted the CCC midsection. The driveshaft is 1.1" longer, so the 727 must not have had the harmonic balancer on the bottom of the crankshaft. The 727 propshaft has a longer spline so will accept the high rake Mercury props. I also have a CCC gearcase with that propshaft (not the one pictured). The skegs are different. The gear lube filler holes are located differently. Notice the extra material as the GC meets the cavitation plate area. It also has a slightly different
shape in that area. I did not get into the unit very far, but did remove the waterpump housing.
Jim Nerstrum explained to Greg about how the gears worked in these units. I can't remember the details. I believe there were three gear ratios that were changed by replacing just the top two gears. Think the rations were 17:19, 18:19 and 19:19 and that they settled on the 18:19 ratio. Jim N will recall.
I did mount this unit on my Johnson RS midsection (took the stud set out and clearanced the mid just a bit at the water pump) but never ran it.

[Powerabout]

Hi Roger
Did it have 3 gears under the waterpump to allow ratio change?

[Steve Pinson]

727 vs CCC: A couple of things that aren't too obvious from the photos: There is an extra pair of mounting studs. The water pump housing is a bit wider and
contacted the CCC midsection. The driveshaft is 1.1" longer, so the 727 must not have had the harmonic balancer on the bottom of the crankshaft. The 727 propshaft has a longer spline so will accept the high rake Mercury props. I also have a CCC gearcase with that propshaft (not the one pictured). The skegs are different. The gear lube filler holes are located differently. Notice the extra material as the GC meets the cavitation plate area. It also has a slightly different
shape in that area. I did not get into the unit very far, but did remove the waterpump housing.
Jim Nerstrum explained to Greg about how the gears worked in these units. I can't remember the details. I believe there were three gear ratios that were changed by replacing just the top two gears. Think the rations were 17:19, 18:19 and 19:19 and that they settled on the 18:19 ratio. Jim N will recall.
I did mount this unit on my Johnson RS midsection (took the stud set out and clearanced the mid just a bit at the water pump) but never ran it.

Hi Rodger hope you are keeping well I am sure the 2.5 OMC crossflow ccc gear ratios we ran in Europe were 15/17 but the failure rate was high we also ran 16/18 ratio they thought they may last longer but they still failed often I think in 1978 nearly half the races I ran ended in gearcase failure.

[RogerH]

Hi Rodger hope you are keeping well I am sure the 2.5 OMC crossflow ccc gear ratios we ran in Europe were 15/17 but the failure rate was high we also ran 16/18 ratio they thought they may last longer but they still failed often I think in 1978 nearly half the races I ran ended in gearcase failure.

Good to hear from you Steve. Missed you att Tavares in November - it was well attended by the OFF gang. Yes, I also heard about the frequent
gearcase failures and think I have a picture of them changing one at a race. The whole 727 happening was cloaked in such mystery that I have no wonder there is so much "fake news" about this motor. Anxious to meet you some day. I do remember that the 727 gearcase had the ratio that
Jim Nerstrum said was the best. And it only had two gears at the top, so I have no idea how they made the gear ratio change by replacing just the
two top gears. It had something to do with the "bottom end" gears/mechanism. Will likely take Jim Nerstrum to explain it.