vindee

I have a 40 size 182 Cessna ARF which I built and installed Carl Goldberg Floats on. I'm running an OS 52 Surpass and a 12 X 6 prop which is not enough power to get out of the water. I can break the surface but not enough speed to fly.
The plane weighs in at 8.4lbs, and with the 12x6 prop it runs at 10,000 rpm. Practical RPM is 13,000.
I was thinking of going with the OS 56-FS which I could swing a 13 X 6 or 7 prop. Would this be enough extra power to fly this plane or do I need to be looking at something else? The 56-FS is a drop in replacement for the 52 Surpass.
Thanks
Steve

Crash-RCU

You are using about the heaviest floats avallable, I would go with an OS 70. I have the Great Planes 40 size 182 Cessna on floats and I have a Saito 91 with a 13X8 prop on it and it gets off the water great, but most of my flying is done at half throttle. I am thinking about going to a Saito 72 which should be just about right.

vindee

Thanks for the reply Garry,
I even covered the floats with 3/4 oz cloth and paint. They look nice , but heavy.
I will look into the OS FS-70. I am running that motor on a P51 Mustang, and the Saito 80 on a Four Star 60. 
I like them both but thought they might be too big for this plane.
Thanks again
Steve

vindee

So if I go with a 70 or 72 size motor, would a 13 X 8 prop be a good choice?
Thanks

scooterinvegas

My Feedback: (1)

I would get the Saito 91. If its too much (doubtful), but if it was, put the 80 from the Four Star on the float plane and the 91 on the Four Star. I have a Four Star with a 91 4 stoke. Perfect.

jimmyjames213

My Feedback: (2)

nope 13x6 is the prop you are looking for

vindee

Don't mean to sound ignorant here, but if I'm currently running a 12 X 6 and can't get it off the water, just going up 1 inch on the diameter ( and the bigger motor of course) is going to make the difference?
I guess I need a little more explanation on how this all works out.
Thanks
Steve

jaka

Hi!
13x8 is a .91 four stroke prop size!
A good start would be a 13x6 or a 14x5N APC or RAM prop. Never use white tip MA props!!!

Minnreefer

I hate to say this, but I would look at different floats. I have some of those floats, but I am not using them. try www.seaplanesupply.com for foam floats.

vindee

Talk about shifting gears. I was all prepared to buy a motor, now after contacting Seaplanesupply maybe floatsare all I need.
I think I will try a set of foam floats first before buying the motor.
Thanks
Steve

vindee

After doing some calculations, with new floats I will only be dropping 1lb. from 8.5 down to 7.5lbs.
Now I'm thinking new floats and upgrading to the OS FS 56 with a 13 X 6 prop.
Would this sound reasonable?
Thanks
Steve

jester_s1

Dropping a pound is huge. If you can almost fly as it is, dropping a pound will surely fix the problem.

vindee

Thanks Jester,
I guess I'll start with the floats first. I am ordering the floats today. (Flat bottom square top) I found out I can go with 32" floats instead of the 34" I originally planned for. That for sure will shave a good pound + off the weight.
My Carl Goldberg Super Floats are 36.5" and weight 15 ounces each. I'm running dual rudders and it turned on a dime when taxing so I think I'll go with one rudder on the new floats to shave another ounce or so .Thanks for the insight.
Steve

jaka

Hi!
13x6 on a .56 four stroke is too large...at least is for a Saito .56. 12x6 is more suitable!

vindee

If I'm only getting 10,000 RPM with a 12 X 6 should I shoot for a higher RPM with another prop or run at 10,000?
Thanks

jester_s1

You'll probably find in your manual that the max recommended RPM of your 4 stroke is around 10k. If you exceed the max RPM, you'll float the valves which will eventually cause an engine failure. 4 strokes are ported to make their horsepower near their max RPM point, so there is no benefit to revving them higher anyway. So prop it to top out at or just below the max rpm point for best performance and engine life.