not sure if this would work for you but its a square insert for standard collet
https://zippkits.com/index.php?main_page=product_info&cPath=85&products_id=608
do not use EC5 they are too small for out boats. Get QS8, 8mm bullets, EC8
these are the best Ive ever seen and I highly recommend
https://www.smc-racing.com/index.php?route=product/product&path=66&product_id=762
it looks like an 1/8th scale so it will use 8s. 850kv is about perfect something like a TP 4070 or a 5692 rocket RC motor. the goto bad boy ESC is a Castle XLX2. budget esc ZTW 200A. I'd personally get a set of SMC HCL-HP 4s packs wired in series for it.
netting was an experiment to collect leaves and debris. it caused too much drag and its gone this season. motor pictured is a 3536 I think. It now has a 3548. It is about 24" wide I think.
I retrieve gas cats, hydros, backlashes, etc with this. I made it 4s with a 12x5 prop this year for more weight and power. it will in fact push or pull a full size jon boat.
these are actually pretty nice I have a couple, actually nicer than real zenoah stuf IMO. Takes about 7-10 days for shipping though.
https://www.tit-racing.com/collections/rc-boat/products/gas-engine-cooling-jacket-cover-fits-zenoah-g260pum-for-marine-engine
EDIT: NM cant use the knockoffs