HI Ray
For the BEC to work you need at least 7 volts so either should work but as you have a LiPo I would use that. if your ESC does not have a low volt cut off I suggest you use a device between the receiver and ESC to protect the LiPo from over discharge. Unlike a plane you will get little indication with a boat.
You will be running the motors above their rated voltage so there may be a heat problem which may require water cooling. A quick circuit round the pond should indicate if this is a problem.
If you can program your Transmitter to give reduced output to the ESC this should help.

Dave

HI Dave just a quick note the setup I am taking for my model is one single 20amp esc bec but I need a bit of advice on which size battery to use I mostly have lipo's 11.1v 2200mah and 7.2v 1800mah ni-mh are any of these suitable I'm not sure about the ni-mh because it is only 7.2v as you know I'm running 2 6v brushed motors.If you could advise which battery I would be most grateful.

Ray.

No problem if you are attending the E Port show on 7th & 8th March I will be on the Crewe & District MBC stand in the Rolfe centre.
Dave 😀

Cheers dave thanks for the brilliant advice I will get the odds and bobs together and make a start on it I will keep you posted if I have any problems I will ask if that's OK.

Ray.

HI Ray
Nice looking model, should look great on the water.
Motor are brushed and are possibly of German manufacture such as Deccaperm.
At least all the info is there with a current range of 0.9 to 7amps at 6v giving a max wattage of 42.
I agree the battery was probably as you thought. There is a simple push switch for on off and I suspect there was a simple Bobs board controller worked from a servo to control direction and speed.
27Mhz equipment will be fine if this is already to hand. You will need to check the frequency is clear if you are in a public space. There are several Clubs in your area who should be happy to help you get on the water.
15amp escs should be fine. This is not a big model and weight will be a problem so a SLA may be a bit on the heavy side and a Nimh would be much lighter. You can get these at 7.2v and 2200mA or higher. You will need to modify the battery box to suit your battery.
As you will have 2 channels I would opt for a Y lead from your receiver to feed both ESCs from one channel, the other channel going to a rudder servo.
I did mention a mixer but for this type of craft I personally don't think it will be required.
As space is limited your ESC will need to be compact. There are many suppliers on the web and modern ESC's come with built in BEC circuits which will power your receiver and servo saving a receiver battery weight. Each ESC has its own BEC so if you have two you need to disconnect the red wire from one ESC to the receiver and tape it up.
If you choose Mtronik they come with their own switch which will remove the need for that push switch which is I suspect a bit lightweight for a modern setup. I suggest you look on the web to see what ESCs are available as the costs vary quite considerably. Many buy from China but expect to wait for a few weeks for delivery and if faulty replacement is not easy. Make sure you get a brushed controller as the web is full of adverts for brushless controllers.
Initially I would just use one ESC with a 15 amp fuse in the red lead near the battery to see how it performs. Connect both motors in parallel but make sure the props are both turning in the same direction. The existing wiring should be correct as connected.
Hope this helps. Please keep us posted
Dave

HI dave posted pic of the inside of model thats if I have done it right on the motors there is a small label on each one with
type 6v
J leer ca, 0.9A
J max ca, 7.0A
now wether these are brushed motors which proprobably they are I wouldnt of thought they are brushless it does look to be a fairly old setup. Would it be ok to install a 27mhz 2 channel receiver and also what battery would it take looking at the battery well it looks like they used a 12v square ever ready battery but I may be wrong. I took what you said about the esc did you say to give each motor its own esc and connect to a mixer to the receiver. Any how let me know if you receive the pic.

Thanks ray.

HI Dave yes I will try and send photos of the inside of the model being new to the forum I will have to figure out how to upload the pics so bear with me.

Ray.

HI flyingfox
Welcome to the site.
As you already fly model aircraft its possible you already have some RC gear. if this is not on 35Mhz you may use it for your model boat. Most modellers are now using 2.4Ghz sets as it removes the problem of frequency clashes at the sailing site. if buying new this would be your best option.
Two brushed motors can be powered by a single ESC or two ESCs. if your receiver is two channel you would need a Y lead to feed each ESC from one channel. You can get better control using 3 channels but not everyone likes this choice as a certain amount of dexterity is required, but could be second nature to a flyer. There are electronic kits that mix the two ESCs with the rudder allowing you to use just two channels if you wish to expand your system.
Regarding an ESC size this depends on the motors installed. Basically the ESC should be able to supply double the rated running current of the motor. if you are using one ESC it would be double that required for one motor. Problem is if one motor stalls (weed etc) the current will go to the stall current which will be much higher than the running current. Personally I always separate ESCs for each motor for this reason.
Can you post a pic of the inside of you model showing the motors and battery space? Any detailed markings on the motors? This would help to decide which ESC(s) and battery might be suitable. Many now use NiMh in place of SLA's and LiPos can also be used if you are already familiar with the technology.
Sorry if this is a bit basic for your needs but hopefully I have given sufficient guidance. With a bit more info a suitable ESC chosen.
Dave 😀