I have the exact same engine and had to replace the ps2 5 volt board, they have to be replaced with a PS 2 3 volt bolt if there still available. I do have one but you have to also change the speaker, they make a PS 32 boards but only asc tech's can get them and they are wider then the older ps2 5 volt boards . I would take the engine boiler top off and see what boards are in the engine , I'll bet it is a ps2 5 volt which use's a 8.4 volt battery not a 2.4 volt battery unless the board was changed to PS 2 3 volt then it would use a 2.4 volt battery..
send me an email I would be glad to fix it for you, they are a great running engine with great sound ounce upgraded to a PS 2 3 volt board
take the engine cover off and take a picture of the board , ill bet is has 2 copper strips on the back side which would make it a PS 2 5 Volt board!
Alan