Expert Advise Required - Swamp Boat Refit

Good Morning Shipmates

Took my newly aquired swamp boat (second user) for a test yesterday - unfortunately it did not go well so some advise needed.

The problem - if chugging along at half power things are great but the boat is a little slow - so I increase the throttle and affter a couple of seconds the motor cuts out :-( . This is easily reset by just giving it a little kick astern. On trying againg exactly the same thing happens everytime.

Hardware - The Speed controller is as in the picture (unfortunately I have no knowledge of these as on my standard models i use either Mtronics or FTX ESC's) - I am using a NiMh battery rated at 7.2v 8000mah (sourced from Aliexpress) - so far I have avoided LiPo batteries - as I have a collegue that has had two workshops burnt to the ground with Lipo batteries although I have no more details than that.

My thoughs - Either the ESC is naff or there is a problem using a NIMh battery with the ESC/Motor combination - what are your thoughts - I dont know where I could source another ESC in the UK and how expensive it would be - I dont want to spend a fortune as I cant think of where I would use another ESc of this type. As regards Lipo batteries as I said so far I have avoided the due to the fact they are expensive and I would need to buy a new Lipo charger again an expensive option in the UK but this could be used in other models.

Anyway guys what are your thoughts, any advise appreciated.

Have a good weekend everyone

Pat