Vintage OS and Enya 2s Engines identification - RC Groups
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Jul 04, 2006, 08:55 AM
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Vintage OS and Enya 2s Engines identification

I have aquired 4 vintage engines 3 OS and 1 Enya I was hoping someone could tell when approx they were manufactured and specs

The Enya is a 29 Model 5224

OS Max III 15 and it is stamp 65 I on the bottom of the mount

OS Max III 15 and it is stamp 66 G on the bottom of the mount

OS PET 099 1.6c with no other markings

Any Help would be greatly appreicated

John Barker
The Sunshine State
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Jul 04, 2006, 09:42 AM
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downunder's Avatar
Have a look at for some Enya info. As for the OS 15, OS have a habit of putting obscure marks under the mount lugs of all their engines and probably means nothing except to the engineers. I checked my 3 crankcases and they're marked 62A, 63H and the last one simply GA.
Jul 04, 2006, 10:25 AM
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JackHiner's Avatar
Check out I just checked it out and remembered the last time I purchased an OS engine was 1963.
Jul 05, 2006, 02:31 AM
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downunder's Avatar
Oops...I forgot you asked for any specs. I don't have anything for the OS but I do for the Enya. If yours has the square intake then it's a 29-IV which was made between 1964 and 1974 but if it has the round (normal) intake then it's a 29-IV B model. As far as I know that was the only change.

Specs for 29 IV-B..
Main bearing...bronze
Bore and stroke... 0.736"x0.704" (18.7mm x 17.9mm)
Volume...0.299 cub inch...4.91cc
Weight... 7.7 ounces (CL) 8.6 (RC)
Compression...7.5:1 (low compression head) 9:1 (high compression head)
Max HP..(CL) .8, (RC) .5
Rev range...(CL) 9-18,000 (that's not a misprint ), (RC) 2-13,000
Recommended prop range....9x5 to 11x6

The square venturi model in CL form also came with 3 different size venturis. Small for stunt, medium for sport and large for highest performance but needed a pressure feed fuel supply. The much higher HP (and rev) figure for the CL version would have been with the high compression head and the largest venturi.

Just for interest's sake, these 29's were a match for any of the best engines in the world when used in CL team racing although I'm not sure if that was for the plain bearing or the ball raced versions.
Jul 06, 2006, 03:26 PM
Registered User
I used one of these 29's in a Dumas Ski-Daddle Too ski boat. It flipped on several occasions with no engine damage. I replaced the 7.5 head with the 9.0 head to see if performance increased any significant amount. When the boat flipped with THIS head installed, the crankpin BENT considerably due to the resulting hydraulic lock. Just a bit of ancient Enya trivia.

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