Appreciate the feedback. Yes, I expect a big outrunner would have more torque to handle a bigger prop (7-8", or bigger). But I would really like to go direct drive to the prop, and I have not seen any big out runners that are waterproofed. Is there something in the 8000W range that is waterproofed?
is outrunner watercooled motor ok?
A flipsky is a great idea. I also have made several outboards with belts and gears etc. Hub motor. Agni 95R motor. Tried so many different options. I found them to noisy to much vibration and a lot of wasted energy. Also gearing at the bottom.
I saw a guy at this forum on plane with a inflatable boat with a flying rodeo with foil mast. Works great.
You boat is a bit heavy to get in plane I think. And for longer time maybe the flipsky will get overheated. But it is so silent , especially with FoC controller Vesc. Just complete silent. And so efficient. So maybe use 2 of them. You can use a cheaper vesc in that case and run even more efficiently because each motor is only running at have the power.
I think it will run way more efficiently than the outboard with belt drive.
Will be so much better than torqeedo I think. They make a lot of noise too. Because of the gearing.
Yeah, my father bought an epropulsion. They have direct drive and are very quiet. Unfortunately the most powerful version is 1kw. Torqedo is very loud.
Why don’t you try a Flying Rodeo motor ? They are the most powerful IP68 inrunner motors for our efoils.
Yes here by @Nace_Erznoznik who has been using it for more than a year now.
An efficient pod for boat mast bottom has been developped Credit Fri-Foil:
Still looking for members 
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Sounds like a really fun project!
I would love to see how long it would take to overheat a submerged 65151 at 21s or 22s and how many amps it could take sustainably at that voltage. Looks like you are running in pretty cold water which is a bonus! If it’s not enough to plane out you could always buy 5 more and do the electric jonboat version of this:
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Ha! 5 ea. Flipsky motors or 1 ea. FR? I have thought about a dual drive option if the single unit is not sufficient, but the $ add up. For the same reason I can’t really start with the FR motor as it seems to be about 3X the Flipsky cost (discounted on Banggood). Looking at the specs for the Maytech 65162 I got excited as I saw the continuous 8000w rating. But in reading through a few thousand posts here I see pretty definitively that the Flipsky, MT, and Reacher motors are basically the same unit, perhaps with different seals and/or bearings, and different specs, but probably the same actual performance. Bottom line seems to be about 130A max, which at 14S (51.8V nominal) = 6734W, which might just barely get me onto a plane, since I found I could do so at 8000W with my old, inefficient PMDC system.
Do you recommend 100KV or 120KV? I am tempted to go with 100 KV (higher torque?) and bigger prop to perhaps get more thrust to get up on the plane, even if I have to sacrifice some top end speed.
Anybody have a scratched up motor they want to sell cheap for testing (mine will be housed inside the lower unit housing so not very visible)? 
In terms of ESC, I am tempted by VESC as I love capturing data, but it looks like I could save a bit by perhaps starting with the 200A Flipsky unit, and I typically use an amp/watt meter built into my battery packs anyway (and DC clamp meter during testing). Do you suggest otherwise that one of the VESC units or 300A rating are worthwhile?
Great to see the boat/board hydrofoil link here - fun stuff.
I have been thinking how nice and light a foil mast would make the entire unit, but the Maker in me loves the idea of re-use of the old outboard units - I know there are hundreds if not thousands of them at end of life and like the idea of handing off a proven retrofit design to the Community College at Lake Tahoe and elsewhere so the kids there can make some $ selling these retrofits, and learn some great skills in the process.
Of course the old windsurfer and kiteboarder in me can’t wait to scrap the outboard conversion and use all the parts for a DIY efoil board. Just picked up a SUP cheap at West Marine for $200 that had been dinged in the nose in shipping, thinking I can cut the board in half and use the rear half for a DIY foil board.
Keep up the great feedback. Thanks, Steve
Why don’t you just buy Elco Boat Motor? EP-15 might be OK and perhaps you can try before buy?
I was just looking for an antenna and found this. Looks like there is a bigger option on the scene:
Been around for ages, but too much drag at 20mm extra diameter.
I like the relatively high rated power of the 86165, but the extra diameter won’t fit in the outboard lower unit (max that I have bored out to is about 67mm). Sounds like the 85165 is a bit wide also for the foil boards for your relatively high speed, Might be ok for an outboard on a foil-type mast, with a bigger prop. But the options for the 86165 seem to all be somewhat higher kv, whereas I think lower kv (e.g. 100) might be better for boat, again with bigger prop such as 9". Thanks for the input.
And Lingvo, thanks for the ref to the Elco outboards. much better pricing than the Torqueedo units, but basically are the same config of what I have as an outboard conversion now, and thus have more noise and losses and need for cooling with multiple drivetrain gearing elements, rather than direct drive submersed motor. I really am aiming for the great electric vehicle smooth, quiet, efficient, torquey feel.
Some update: I have the Maytech motor embedded in the lower unit and operating with the Maytech 300A ESC, which I am in process of mounting in waterproof box along with gauges, etc… I have the Maytech 7" prop that came with the package - I sense that people have not had the most luck with that. I’ve read though most of the 800 posts re props on the 65161/2 motors. FR seems the clear winner for foiling but not certain performance will be same on outboard. I am tempted to try an 8" prop also. Anyone gone that big with this motor? My primary goal is to get the boat up on a plane, and not on top speed or efficiency. I can easily fit 14S 120Ah batts under the seats of the boat. I would like to get 7000kW of power. Any chance of that with 14S and the right prop?
If you can see and hear this as video and not just photo, you can hear that there is some “cogging” at lower speeds but smooth from about 30% to full throttle. I have ESC firmware that has zero speed at center 1500 msec pulse width, and goes from zero to full and zero to full reverse in either direction for there (800-2200 msec). I was hoping that using both units (motor and ESC) from Maytech I would get smooth performance throughout the throttle range, and maybe I will under load.
Here is the 8"x5 prop from a local used gear chandlery.
Might even try a 9" prop from typical 10Hp-15Hp outboard. But might be too much load for the 65162 motor.
With my earlier motor mounted on the upper unit, with belt drive and gearing, as shown in photos at top of posts, I need at least 100A at 75v (21S) to get on a plane. So about 7500W. But with direct drive and now right angle gears and belt drive, I expect this unit to be 10%-20% more efficient. So 7000W at 14S 52V= 135A. Within listed specs of the motor and ESC, but seems that Jezza and others are measuring max 124A. But that is with smaller prop.
Another question: at these high continuous loads do you think I need to water cool the 300A ESC mounted in the waterproof box? Would love to skip any water entry and exit tubes, but seems likely I’ll need it. Ok with just pressure from forward motion, skipping water pump?
Any feedback on all of this is greatly appreciated. Fun project! Problem is now that my boat is under a few feet of snow in the Sierras and the mountain lake is freezing over. Need to find a test boat in the Bay Area.