HI Richard
I have just added my Sea Queen to my harbour but here are some pics that may be of interest. Sorry no on water shots.
Giant Shark also do Wattmeters. 😀

Hi
if you decide to carry on with this motor Giant Shark site they do a water cooled esc, this one is a seaking, it also has reverse. this is a 120 amp esc
Dave

HI Richard
Just had a quick look at the J Perkins website and seen the spec on your motor. This is a model plane motor equivalent to a 26cc Ic engine.
Electric flight items -> Brushless motors - EnErG
4445830 26cc O/R 390 (C50-30) Brushless Motor
Battery - 5-6 cell Li-Poly; Working current - 50-76A : Peak 80A; Shaft diameter - 6mm
Speed Controller requirement - 85A.
Sorry but in my opinion this is not a suitable motor for your Sea Queen.
Its designed for a model plane with air cooling from the prop.
The battery required is a 5 cell LiPo (18.5v). Popular size is 3 cell and most chargers will cope up to 4 cell but they are expensive for 5 cells as are the batteries.
The motor in water will have a much heavier load than a prop in clean air so the current will be high - possibly above the rated max.
You can water cool outrunner motors with a special water cooled mount that the motor fastens to as part of the mounting and this motor will certainly need cooling.
A three blade prop will be fine but the ESC will need to be watercooled and at least 100 amp continuous. There is a 90amp version on the Perkins website that is watercooled.
There are other brushless motors on the Perkins site that have lower specs and voltage requirements and can use 3 - 4 cell LiPo's. if you could swap this may be a good time to consider this option.
If you intend to continue with this setup, buy or borrow a Wattmeter and battery and see what current is needed with the prop fitted and in the water. I found that using a lower voltage battery caused the motor to overheat and the current increased significantly.
When you have the current drawn you can decide what ESC you will need. Personally I would double the figure you obtain from the Wattmeter to give you a margin of error.
I do hope you can find a satisfactory solution and please ask if you need any further help 😀

Thanks for your response,The brushless motor I have gone for is a JP C50-20.
I can not water cool it as the outer casing of the motor spins when used.
I only got it last week so that I could get the mount and prop shaft lined up.
I still have a lot of the build to go(not got the decks on yet).
My local model shop would sell me a esc with a 65amp rating,someone else has told me to go 25amps over motor rating.
I would of thought that if you have a 85amp motor you go for a 85amp esc.
I have not thought too much about batteries yet,but looking likely to be lipo.
Told that the 3 bladed brass prop that came with kit is ok to use.
Regards
Richard

Hi
I have a Sea Queen with a brushless motor drawing about 27amps and use water cooling on both motor and ESC rated at 85 amps.
I assume you mean the max current for your motor is 85 amps as the actual draw will depend on your prop/battery selection.

You should invest in a Wattmeter to measure the actual current used then make sure your ESC is rated at least double this as manufacturer rating are always optimistic and usually relate to instantaneous max ratings rather than continuous ratings.

Unless your Sea Queen has been built very heavy I suspect this motor will be somewhat over the top for scale speed. if you are using this sort of power then you will certainly need to install some form of water cooling.

Unlike brushed motors brushless need to be able to achieve their optimum speed range and this is best controlled by careful prop selection. I suggest you start with a small prop and work up in size until you get the best result within the motor and ESC ratings.

If you exceed either you run the real risk of damage to either or both.

Not sure what battery you are using but if LiPo do follow the instructions carefully and make sure your ESC has a min voltage cut off set to the battery manufacturers specs.

Hope this is helpful. Please post details of your progress so others may benefit from your experience. A video of the boat on the water would be good. 😀

Hi
The general way for the ESC to be the amp rate of the motor, plus at least 25 amps. this is the general rule to my knowledge, it's better safe than sorry. 😯 I hope this is helpful.
dave