Floats on MT-7-235

[rickpeterson]

I have a 2009 MT7-235 IO-540, McCauly 3 blade CS prop, spring landing gear, stock tires. Empty weight 1,722 LBS. Gross weight 2,500, Useful Load 772 on wheels. She's rated for 5 souls on board though the riginal owner lost the auxillary seat.

I plan to install Wipline 3000 floats. She will be landing on lakes at SL to 5,000 MSL.

Questions:

*How much do the spring gear, mains, nosegear and nosewheel (that will be removed) weigh?

*She holds 84 gallons of fuel. To save weight would it work to remove the auxillary wing tanks or the S-Tec 50 2-axis auto pilot?

*How will the Fuel injected 235 HP compare to a 180HP or 260HP on floats?

*If the 235 needs more power, are there mods that will boost it?

*What is the best prop for the 235HP on floats?

*Do I need to cut out the fiber that covers the float mounting points or just drill holes through the fiber for bolts to pass through? Is there a clean way to hide this area when back on wheels?

*Do any of you "know a guy" that has flown a similar Maule over-gross on wheels or on floats, and if so, how heavy and how did it work out?

*Any general opinions or advice will be greatly appreciated!

[rickpeterson]

I hit reply rather than Edit.

[bobguhr]

I don't know much about the technical points. But I'll share an observation. My son and I have attended the International Seaplane Fly In located in Greenville, Maine 1,028' msl the past three years in a row. The fly in is a two day competition, short take off, spot landing, canoe/water taxi race etc.. Each time there has been a Maule M7 O-540 235hp two blade prop and an MT 7 IO-540 260hp three blade prop. The Maules competed against one another and an assortment of Cessna 180's and 185's. The first year the M7 235 beat everyone in the short take off and the MT 7 placed in the top 1/3 of the pack.
The second year the M7 235 did well, 2nd place, beat out by a Cessna 180 which I believe had PPonk, Riverbuggy could chime in to verify that. The third year I, believe the MT 7 driver had been practicing his technique, the MT 7 was the short takeoff winner hands down beating out the winning Cessna from the previous year. The M7 235 and the MT 7 260 seemed so close in performance that I believe it came down to pilot technique. FYI both Maules were on straight floats.

[MrHRC]

From my limited experience:

Baumann 2750A's (Gross 2750lbs)
Removing fuel tanks would cost $$$ and remove value.
My 235 provides plenty of power gets off the water (and the runway) alot quicker than the Cessna,s I see around. I,m not sure how much 25hp would gain me vs. weight and costs.
Your gross weight should go up on the floats. My useful load is 640 lbs. with the autopilot and aux tanks still in. I weigh 200lbs and can afford to lose 20lbs. Best place for me to gain useful load is the Pilot.
I have been on a couple of lakes at 3000' and had no trouble getting off the water. 5000' would seem reasonable considering lake size and DA.
I have the 3 blade prop. Runs Super smooth and is quieter than a 2 blade.
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There will be several modifications made for mounting the floats. 4 mounting points, brace wires, and water rudder cables. Once you have amphibs it is unlikely you will put the old gear back on.
Due to my limited experience (300 hrs) i have not pushed the over-gross weigh boundary. I fly at gross-weight regularly and at 2750 she performs great.

I cruise at 100kts IAS 2300 RPM 23"MP 11 gph (IO540)
Pilot 200lbs + Passenger 150 + 43 gal mains 256lbs +36 lbs of baggage = Gross
This means just over 300 NM's with 2 people and limited gear.

Amphibs means parking in a hangar, on secure land, no float dolly, easy access to fuel, but at the cost of another passenger.

I would bet it would be cheaper to sell your Maule and buy one with floats already installed.

[riverbuggy]

The PPonk 180 that bobguhr referred to had everything yanked out of it, and dumped on the dock. I think the only thing that was left in was the pilot's control yoke. Judging from the number of full 5 gallon gas cans sitting on the dock, I'd guess there was somewhere between 5 gals., and fumes on board.

[krautman67]

The M5 must have a "float kit" welded to the aft fuselage at production time, do not know if this applies to your much newer M7, this would be a bit of an expense. I plan on re-working our fuselage to accommodate floats in a few years. I will plan for straight floats to accommodate that extra passenger. I agree with MrHRC, DO NOT remove those aux tanks, I've had them out for painting, they weigh as much an empty beer bottle (unless there is some avgas in it). The M5 will also need an "upgross kit" to bring it up to your 2500lbs. It will make a fine float machine with the 235. No known power boost for the 0-540. You've got the best seaplane prop already.

[rickpeterson]

I definitely will leave the Aux tanks in place.

If anyone has any more friendly advice please feel free to pile on!