My brother and I have several OS four strokes (70 & 91 sizes, not pumped) and they seem totally reliable and are easy to tune. They seem to have a pretty broad adjustment range on the needles.

We also have several Magnum four strokes (61, 70 & 91 sizes). They run very well and are very reliable after break in. Break in is longer than with OS but not bad. The older models (without the oil return to the intake pipe) take a lot longer than the new models. Our experience has been that the Magnums have a pretty narrow adjustment range on the needles. They also don't seem to like running at all rich at idle.

As far as power, with a 14x6 prop and the same fuel, some of the engines of each brand are stronger than the rest.

I like the long plastic throttle arm on the OS better than the metal arm on the Magnum. It makes it easier to hook up throttle linkage. Overall I prefer OS but buy Magnum.

And here i was thinking that you couldnt overpower a plane... that being said I try to stay within the guidlines of the mfr. of the airframe, but almost every plane i build i put in extra supports and braces. no need to be caught off guard with the motor flying and the tail feathers sticking out of the dirt.
dan

At the $30 offdiscount Tower has going on I was able to order the OS 91 surpass w/out pump. Woo Hoo! I'll post pics as I build her.
my next plane will probably be the H9 60 Corsair and I may try out the Magnum XL91. That's a great price and hard to pass up.

Are you saying the OS 91 is too much for the plane? The specs say.61 - 1.00 (2-stroke), .72 - 1.00 (4-stroke)

your going to be happy with the 91 surpass in your Marie, just follow the break in instructions, and you will have a good running engine for a long time to come,mine will sit for months, I just fuel them up and they fire right up I like that kind or reliability.

I have a few projects going on now one will be the H-9 corsair I have in the box I am going to go with the OS in there as well.

its hard to get away from the looks of the MAS props they fit right in with a warbirds,I like the K series like this one http://www3.towerhobbies.com/cgi-bin...9&I=LXZ982&P=K they are pretty good for the price.

The guy in our club who has this model is running a Saito 100. A 91 four stroke is definitely NOT too much for this 60 size model.

Hey guys,
  Well I have my Marie ready for her maiden and have been running in the engine. Went to my LHS to get more fuel and was told that running the OS 91 surpass inverted will make it run terrible and I should run it on it's side... Huh? Of corse this is After I cut the holes in the cowl in which i'm sure you can't get a replacement..  bigtim I see you're running your inverted are you having any probs? I see you said to run it inverted also.
At the moment the engine seems like it's running fine to me.. I'm kinda worried now.

Thanks

Hi!
The white tipped MA props are the worst props you can choose as they are 1. Loud 2. don't perform as well an APC or RAM prop do.