I bought a couple of ready made RC boats about 15 years ago and have been at the back of my garage for that time. Used to play with them on the sea.
So as you can expect they were some wot corroded. Fitted new new twin 12v motors to one and controller.
First mistake:
When I purchased the controller and then fitted to the boat I could not get the controller to work. All the other controllers I had bought, exactly the same were fitted in there models and just worked.
I returned to the model shop and said " Oi you sold me a dud"
They checked it out and showed me that the receiver had not been calibrated to the hand set (oooops big red face)
I had no idea that I could buy a receiver on its own and up till now I have been collecting hand sets for each and every model.
Second mistake:
Any way after fitting the model out with the new power plant with the idea that it would go real Fast (Speeeeeeeed)
I take the boat to my marina. The original model had two little 7.5v motors and was quite fast but now.
Placed the boat in the water switched on and off it went. Boy was it quick. One dash to the other end of the pontoons and back. Brilliant one fast turn in front of me flipped over and sank.

I still have the other old model so I have a chance to learn by my mistake's again.😭