Advice needed 54" seamaid electric drive scale performance

[Givit]

Hi
I am scratch building a 54" seamaid century and need advice on power train.

I will need to push along appox 8-9kg of 1400mm of boat
question what will spin 60mm prop at scale speeds ,,30-50kph. (60mm prop is only scale size i could use smaller)

I would prefur to run around 3-4s 14v batteries or SLA 12v
even a brushed motor but dont think theres any to suit.. maybe small (JOHNSON RS-775 )?

I have a castle 800kv motor and esc but thinking this is mass overkill unless geared down.

What is the normal electric size replacement for a 260pum gas drive line and prop size? as i think this would be good suit but i want electric.
Thanks any advice maybe looking for power calculator?

[Givit]

So in the past i had the local print shop scale up these plans 200% and built for my kids.

Now will build as the 1/4 scale plan. I really need suggestions for a starting point for power drive train. motor,shaft,prop?.
approx 18lb 55"long 13"wide, submerged prop . I can build motor mounts, plates for gears all that. I estimate around 800watts will be needed open to suggestion

I have experince in the rc hobby all will be tested using Watts meter, and am willing to listen and take on board any help in this project.

[Peter A]

That castle is a replacement for a gas motor. On 4s with a 60mm prop you would be somewhere around 35kph. You will need plenty of mah though for decent run time.

[dasboata]

If it's for the kids look for a jet drive or even making one a lot safer

[Givit]

Funny you mention i do have a Swashdrive unit.
no the rc 1/4 scale is for me.
I thought the 2028 would be overkill, well thats good i have existing 4s 6000 graphines for losi 5ive runs 2028.
any ball park amp draw thoughts, as i will need purchase WC ESC 150 maybe?

[larryrose11]

The jet drie would be much more safe with kiddos.
A used golf cart setup may be the easiest to get going. They are usually 48V, and have a built in charger. They usually have a lead acid batteries, (trojan T05, 100 Ah, 6v) which may be fine for this application.
if you want to buy new equipment, this may be a good resource:

https://www.electricmotorsport.com/marine

[larryrose11]

A jet drive for a WaveRunner can be purchased from eBay

https://www.ebay.com/itm/95-96-97-98-99-Yamaha-Waverunner-760-1100-Jet-Pump-Drive-Shaft-Reverse-Assembly/173356777770?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D20160908110712%26meid%3D7b5836580b8c44acb942e41fe635e7e3%26pid%3D100677%26rk%3D1%26rkt%3D30%26sd%3D152173841610%26itm%3D173356777770&_trksid=p2385738.c100677.m4598&autorefresh=true

[Givit]

The jet drie would be much more safe with kiddos.
A used golf cart setup may be the easiest to get going. They are usually 48V, and have a built in charger. They usually have a lead acid batteries, (trojan T05, 100 Ah, 6v) which may be fine for this application.
if you want to buy new equipment, this may be a good resource:
https://www.electricmotorsport.com/marine

That was my prefured drive line for finnished kids boat,but at close to 10k and having 6yr olds doing 30+knts, no.. $200 for trolling motor.

So far with this project for 55" 1/4 scale, from suggestions i will run
4s batts, to ESC???, to castle 2028, to 5mm ss prop shaft, to 50-60mm prop but at what pitch 2 0r 3 blade? to remain around 100amps region
I dont need chine walking speeds just on plane
Thanks