Outboard motor conversion using Flipsky 65151

Hi, I am looking to convert a 1999 Evnirude outboard lower unit to electric for my aluminum skiff. I’d like to use the FLipsky 65151 motor since it seems ubiquitous and a good physical size. I have 14S, 60Ah battery packs. I have bored out the outboard prop drive housing to abut 67mm dia. and about 130 mm deep - should house the 65151 nicely but would love feedback on the idea. I expect to need 6000W or more to get the 13’ boat up on a plane. Can the flipsky motor be operated at 6000W continuously or only for shorter peaks? Do you think there will be enough power to get the boat up on a plane? It needs about 8 hp with heavier gas engine. Can I overdrive the motor to perhaps 7000 W briefly to help get on a plane? I have converted another 15hp evnirude to electric with a permanent magnet DC motor where the powerhead was at the top of the unit, with belt drive for 2X rpm to 6500 rpm and I get about 23 mph on the boat - much better than the gas engine. But it is heavy and more noisy than I would like. With that config I draw about 100A minimum (220A max) at about 80v (21S) to get on a plane. But there are losses in the belt drive and the driveshaft to the lower unit and then right angle drive to the prop, so I might be losing about 10-20% efficiency compared to using the Flipsky as a direct drive underwater. Do you recommend the 100KV motor for higher torque to drive a larger prop for this config? What is max prop size reasonable with this motor and 14S? Which ESC do you recommend?
I will try to post some photos of the bored out lower unit.

There are lots of these early 4-stroke outboards available cheap or free as donor assemblies for this type of conversion. Cheaper than a $5000 Torquedo :slight_smile:

The donor Evinrude gas engine complete is about 115 lbs. The DC PM motor conversion is about 80 lbs. And I think the concept describe above will be about 35 lbs, all not including batteries, which fit under the middle seat of the boat. Of course the next step would be to replace the old lower unit with an efoil aluminum mast, still perhaps using the Evinrude transom mount. There could be significant demand for such conversions in the Sierras in CA and around the country, as people migrate to electric drive. Mine is used at a lake near Tahoe at 7500’ with off-grid solar to charge the batts.

Before I spend $600-$800 on the motor and ESC I’d love to get feedback from this learned group as to whether I am likely to have enough power to get the boat on a plane. Thanks so much!

Here is the old configuration with DC PM motor and belt drive.

You need a big Outrunner, flipsky is too small for this Projekt.

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 :flushed:


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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)? :slight_smile:
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?