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Mar 30, 2009, 02:41 PM
Registered User

Question OS Max 15 and FP signify?

I have an old engine I'm trying to sell. The box says OS Max 15 FP, but someone told me it's just an "OS Max 15". Is there a difference?

What does FP mean.... sleeved bearing or something? Before the FP's came out did they have an OS Max 15 and how would I be able to tell the difference.

I don't know to much about fuel engines so any information would be appreciated.

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Mar 30, 2009, 02:53 PM
And You're Not
Here's a pic of each.
Mar 30, 2009, 03:57 PM
Registered User
Thanks for the pics. The only difference I can really see is that where the marking on the cylinder is on a raised area on the FP, and not on the other. I wonder what the differnce is internally? Is one engine better than the other? Would one be worth more than another?

Thanks again.
Mar 30, 2009, 04:28 PM
Registered User
What are you asking for it Dave?


Mar 30, 2009, 07:45 PM
The Tree? Yea I can hit that!
I could be wrong but I thought that the FP was the older brother to the max.
I do know that o.s. is really good to change just enough to make parts hard to get, or at least that is the problem I have with mine.
Mar 30, 2009, 07:56 PM
And You're Not
The FP is a newer design by quite a bit, the pic I posted of the Max 15 was from 1975, the pic of the 15 FP was from 1987.

The OS time line is posted Here
Mar 30, 2009, 09:32 PM
Registered User
The old os max 15 has a baffle piston while the FP15 is a Schneurle port engine.
+ a few more things.

Mar 30, 2009, 10:40 PM
Registered User
I noticed also on the side opposite the OS 15, there is an "FP" marked in the casting.

Thanks for the links and the info guys! I can always count on RC Group forums for great information.

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