When you say % meter what are you actually measuring? if you are checking voltage then you are reading a "no load" figure get some one to hold the boat in the water go to full throttle and take a reading then.

A lead acid battery is taken to be fully discharged at about 1.95V per cell ( for a 12V battery 11.7V) no load and 1.75V per cell ( 10.5V for 12V battery) on load.

Discharging below these figures can lead to damage. "Deep discharge" lead acid accumulators can go lower.

Quite simply if you want to go fast for longer you need a battery of greater capacity. Consider the battery capacity as a fuel tank. LIPO batteries have the best capacity weight ratio BUT they require great care to keep them in good condition.


Ohh and listen to Dave M BUT take care he will lead you into temptation grins thanks to him I now have a Fr Sky TX RX setup and am playing with a quadcopter and if you think the control setup for a boat is complex you ain't seen nothing!!!!

HI Richard
I agree with Flack. The SLA is not a good choice for a brushless motor. Basically the motor is a low resistance device that needs a low resistance power supply. SLA's have a realtively high internal resistance which limits the current they can deliver. The best batteries are LiPo followed by NiMh with SLA least suitable.

Nimh batteries of 5000 Mahr capacity will give much better performance and the reduced weight will improve the models overall performance.

You have not said what prop you are using but generally brushless motors work more efficiently with smaller props than those used for brushed motors. ideally you need to connect a wattmeter in circuit and see how many amps the motor and prop set up is drawing. You should adjust the prop so that the current is within the range of the motor /ESC/battery. if you exceed the max values you will generate lots of heat and run the risk of damaging the motor and/or ESC.

I suggest you borrow a battery of a fellow club member and see how it performs.

If you have the funds and really want the Sea Queen to fly then a LiPo will match the performance of the IC engines originally installed. This is not a cheap option as you will require a dedicated LiPo charger, charge bag and your ESC needs to have a cut off voltage to protect the LiPo. Please do some research on LiPos before you proceed as they are new technology and require much more careful treatment than NiMhs.

I am attaching a pic of my Sea Queen setup. Both the motor and ESC are water cooled and I use a 11.1v 5000MaHr LiPo.

Good luck and please let us know how you progress
Dave 😀

You don't say what mAh your 12 volt battery is, a 12v 4mAh lead acid battery will give a lot less run time than a 12v 7mAh one. Lead acid is probably the least favourable power supply for a 46 inch Sea Queen with a brushless motor, brushless motors tend to want to draw their power faster than a lead acid battery can give it which could account for the slow speed whilst the battery is still showing a high % of its capacity left. The Sea Queen at 46 inches is a big model and its all wood construction makes it a relatively heavy boat to move through the water, the prop size can also have an effect on the run time. I have the Aerokits Solent Lifeboat which is similar in size at 49 inches and weight, I run two MFA 800 brushed motors with three bladed 50mm brass props on 2 x 8.4volt NiMH and can achieve run times in excess of an hour, admittedly speed wise it isn't as fast as the Sea Queen would be. it would be worth looking at changing the Lead Acid to NiMH, say 12V 5000mAh (35 Amp discharge capability) which would improve things substantially, if you are a member of a club maybe someone with such a battery would allow you to try it out before outlaying the £40 it would cost for such a battery. Afraid I have never been a fan of LiPos but I'm sure that somebody on the site, maybe Dave M would be able to advise on their use.