Thanks Dave for your information.
Regards
Paul

HI Biggles
Gone rather quiet on the suggestions for a brushless. I have little knowledge of the Marx Chris Craft Constellation model boat and was hoping another member would make a suggestion.
It's not a large model and two turnigy d3536/6 1250kv may be a bit too much. The numbers actually relate to the length and circumference dimensions in mm and the kv rating is the number of revolutions per minute for each volt applied, so for the example a 10v battery would result in an open max speed of 12500 revs.
You could try two 2826 with a kv of round the 750/1500 mark. Most sites give stats regarding the power output and current draw and suggested ESC max capacity. The larger the motor the heavier the current and dearer the ESC. Battery capacity needs to be considered as weight will be a problem even if you use LIPOs.
If the props load the motor too much it will get hot as will the ESC so you may need to fit water cooling. A wattmeter will indicate the current drawn by each motor and can help you keep within the rated values. There is a balance between motor and prop and often a smaller or finer pitch prop will increase the speed and reduce the amps drawn.
Good luck with the upgrade and please keep us posted with your progress.
Dave

Thanks you for all your help, any suggestions on what size brushless motors I might need.

HI Biggles
If I may just add to Mark's reply, yes you do need two ESCs. Brushless motors run much faster than brushed and the original props on your Chris Craft may be a tad on the large size. This may cause your motors and ESCs to overheat so you need to check this on the water after a short test run. if you have or can borrow a wattmeter this will help measure the amps used in the water.
Brushless ESCs can be reversed via the transmitter but many do not. in a fast boat this may not be a problem but it is something to consider. as Mark says you can set the direction by altering any two of the three leads so no problem with contra rotating props.
I agree with the comment about Imported ESC ratings, and whilst some seem OK many fail and its a long way and wait to get a replacement. There are several on line suppliers in the UK offering suitable motors and ESCs and in my opinion they compare favourably in price with overseas suppliers.
Dave

Forgot to mention, some chinees ESC have odd values! Chinees amps sometimes dont match UK amps, if you are buying an unknown or un marked ESC of ebay, double the amps that you want. IE 25 amps buy 50 rated.

Some are brilliant some not so

Mark

Thanks for your advice Mark, its much appreciated!

HI Biggles

No worry with running one motor in reverse, all it means is that one set of wiring is different.

Be aware that the ESC for each motor must exceed the max watts, just incase you pick up some weed etc. The fuse wont blow quick enough to save the electronics.

Hope this helps

Mark

If I ran twin brushless, one of them would need to run backwards, is this possible? I have twin prop shafts, rudders etc. I suppose I'll need 2 speed controllers.

Any one else running a twin brushless set-up?

Any help gratefully received.

Thank you All.

Am thinking of using brushless in a new build so info is very useful
Thanks

HI Dennis
Welcome to the world of brushless.
Should you decide to change to LiPo batteries please ensure you use the low voltage cut off for your ESC as LiPos need much more care in use than NiMhs.
I have used brushless for a few years and the only problems I had were with the motor mountings vibrating loose. With an Outrunner you have no warning before the motor self destructs. I now double check all my mounts and connections before each sail.
Be good to see a video of your Sea Commander on the water. 😀

😊 hi I have just fitted one turnigy d3536/6 1250kv in a sea commander and it planes and goes faster that the ones supplied in the kit I use 8.4 volt mah batterys and I am going to change most of my boats to them. 👍

Hi.
I would suggest that you research, and consider a pair of smallish, if you are firm on using two, brush less motors using lipo batteries. You will save a lot of weight and have an abundance of power depending upon set up. I have a scratch built 34 inch ply semI scale cruiser (See picture in my profile when running with Ic engine) now fitted with a Turnigy 750KV High Torque Outrigger and it is 50% quicker than with previous motor an OS 35 (4.86cc) engine. My pal and I are fitting this same Turnigy Brush Less motor to our 34 inch Vosper Fireboats. I once had an MFA 850 in a ply 49 inch Perkasa and it planed fine so two in a boat at 30 inches could be excessive.
Regards
Willy