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Old 03 June 2010, 11:07   #1
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1970s OMC prop chart?

OK, here's one for the historians.

Looking for info from an early 70s OMC prop chart for a '72 Fastwin / Sportwin (20/ 25 HP).
The "as supplied" props were 9" & 10" pitch, but I'm wondering how high or low the pitch range went for these machines.

It's a "solid hub" type - not thru' prop exhaust. Proper oldschool
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Old 09 June 2010, 10:30   #2
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Quote:
Originally Posted by 9D280 View Post
It's a "solid hub" type - not thru' prop exhaust.
they still do have a friction hub along with the shear pin... double protection.. so only "solid" looking

I actually have a factory OMC 12P stainless! on my 1973 25HP- it's a rare one.
part number of it is 389320

it has too much pitch even for 1 person in my Avon 3.4, so I'm not sure what application it would have... racing only I suspect... i.e. seaflea or, for twin 25 applications

I would like to have an inch of pitch taken out - is that possible with SS props?

the 10P aluminums over rev my 25's I have 3 of the 22CID motors

a 1973 25HP Johnson
a 1975 25HP Johnson
a 1975 20HP Evinrude
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Old 09 June 2010, 10:33   #3
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from a1 prop http://www.a1discountprop.com/omcoutboard.htm

MODELS - 15HP ( 1953 - 1956), 18HP (1957 - 1973), 20HP (1969 - 1973) & 25HP (1969 - 1977) (PIN DRIVE)
9 1/4 X 7 3 ALUMINUM SEE MICHIGAN WHEEL PART MI 012102 OMC 388294
9 1/4 X 9 3 SST WORKBOATS OMC 389390 $393.00 $295.00
9 X 9 3 ALUMINUM SEE MICHIGAN WHEEL PART MI 012109 OMC 379717
9 X 10 3 ALUMINUM SEE MICHIGAN WHEEL PART MI 012011 OMC 383629
9 X 11 3 ALUMINUM 12' - 16' WEEDLESS OMC 592959 $151.00 $113.00
9 1/4 X 11 3 ALUMINUM SEE MICHIGAN WHEEL PART MI 012013 OMC 388088
9 1/4 X 12 3 SST HIGH PERFORMANCE OMC 389320 $408.00 $306.00
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Old 09 June 2010, 11:22   #4
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from http://www.propcopropellers.com
all are $75! nice

15, 18, 20, 25
Pin Drive

Not Thru
Hub Exhaust


53-77
C AL 9 x 10 1/2 3 F7 381801
C AL 9 x 10 3 F8 592959
HL AL 9 x 9 3 F9 379717
LL AL 9 1/4 x 11 3 F10 388088
SW AL 9 x 10 3 F11 383629
W AL 9 x 10 3 F12 592959
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Old 10 June 2010, 05:14   #5
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Hystat,

Brilliant! Thanks.

I suspect putting a SS prop on will quadruple the value of the engine (and that includes the fuel in the carb bowls! )

It's pushing an 11' Dory along, flat bottom, so I was expecting a lot more top end speed, bearing in mind I had a Suz 25 (granted 20 years younger) on an Avon SR4, and it had a 13" which worked well.

Follwoing some teeth breaking antics last weeekend, we're giving very serious thought to swapping the dory for an Avon W350/400 kind of thing. By trhe looks of things we might not want to swap props just yet!

Cheers.
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