HI there.
I have a new in box Greatplanes Extra 300 ARF 40 size airplane as long as an OS 91 FX engine.
The question is simple:
Should i use this OS engine?
Or,it is better to use another engine because the power of this engine is too much and will probably
result in problems with handling in flight and/or structure problems in fuselage-wing?
Thank you.

Kostas1,

Yep that engine is too much for that plane. For a two-stroke probably the OS50SX would allow orbital work on that plane and is just a tad heavier than the OS46AX with way more power

Definitely too much motor. Go with what Bubbagates recommended. Great plane/engine combination. Those 2-strokes would be great for this plane, or an OS 70-FS 4-stroke would be good for that plane too. That would let you swing a little bit bigger prop and would give you some extra pulling power.

Hope this helps

Ken

YEs,it will have too much power but what's the problem?
That's what i am asking you.
It will be any problem if i will install this engine?

Kostas you will have several problems installing this engine

1) the fire wall will need to be beefed up and the mounts modified(added weight). IMHO the firewall is a bit weak to begin with and you want to hang more motor off it...you'll also have trouble mounting the cowl with the extra length of the 91.

2) CG will be a problem with the extra weight of the 91 on the nose... your already adding weight by using the heavier motor and will likely have to add more weight to balance it out... this, on a plane that's IMHO is already a bit heavy when built to spec... wing loading will be higher and I hope you already know what that means.

3) Prop clearance... you'll need to swing to bigger a prop on the 91 and won't have much clearance unless you put on taller gear... more weight


Extra power is good on most any plane IF you know how and when to use it... this is NOT a 3D plane and never will be... the extra power will be for the most part... useless.

John

So,
what engine do you suggest?
I want to have unlimited vertical,so the engine must be very powerful.
How about the OS 61 FX or OS 65 LA?

I like 4 strokes myself... YS 63, Saito 82 would be MY only choices.

I think you'll be happy with any of the 50 something 2 strokes or 70 something 4 strokes... vertical will not be lacking.


Depends on YOUR idea of unlimited vertical... too some it means pointing the nose up and gaining altitude even if you have to fight the plane some what... others want the plane to accelerate as it's going straight up and out of site... yet others will want to be able to roll and do a few snaps on that up line... all require different amounts of power


John

If you want truly unlimited vertical then the OS61 series will still be too big but will do the job well but now you are into mounting and balance and weight issuesprevio. As I said previously, the OS50SX will give you that but if you really want power in light weight package then the YS63 is the choice. The power output on 30% nitro is the same as a Saito 100 and the near perfect prop is the APC13X6. If you use 20% nitro you are looking at the power output of a Saito 91

I have one of these in a Great PLanes Cap580 40 size that weighs 7 lbs even and it will hover at 1/4 throttle and go balastic out of that hover. Now you may think to yourself I'll just get the Saito 100 because its cheaper. Well then you are getting into the ability to mount it to the airframe let alone balance it. The YS will be easy to mount, fits in the same mounts as any 46 size engine out there but you will pay allot for this engine and it will be finicky until you get it broke in and dialed it but once you do you'll never go back to another 4 stroke. I own several YS engines and all make gobs of power

Yes,power on Ys engines is BIG!
But,and here is the "problem",
i have in my Extra a YS 53 FZ,and this damn engine doesn't work.
Em,sorry,it works well in idle but when you advance throttle to peak rpm,the engine slowly stops.
I checked all,needle settings,fuel lines except of the check valve!
So,i will not pay too much $$$ for an engine that will not work.
Ofcourse other YS engines like yours,are working as you said very well,but why i should trust any more this Japanese engines?
Also,i don't know how the new YS 63-S is working.
I have seen the YS 63 FZ working,reliably i think with tones of power.
What's your oppinion about installing the OS FS 70 Surpass or the new OS 70 FS ULTIMATE?
Also,the OS 70 FS ULTIMATE is lighter!

Sorry to here about you YS issues. The 53 was known to have regulator issues. Almost all YS problems I hav e ver fixed have been a stuck regulator or another thing is if you use fuel with any castor in it. Castor will plug the small holes in the regulator body over time.

Anyway, either of the OS70 4 strokes will be fine in that plane