IHello buddy, i recently buy a used one. I'm a electronic and elctric engineer, so i rebuilt it. I have already the batteryes , it was just to create some wiring and repair t the trigger. I've tried up to 56.3-meters and was not flooded. I use it mainly for the onward way, I go back to the surface and retrieved from the baoat at the end of decompression. This way i have around 45' of burning, this means in-line around 1.5 km. It depends of what you want, just a check or a complete revision. There are 3 ways of water to check: the main "O-ring" with guide pieces, the o-rings of the recharge tap, the motor seals. About the first two, you have just to clean and check. For the motor, if you want, but i don't think it's necessary, go to boat service who sale Minn-Kota or Evinrude or Johnson: in fact, the motor is a Minn-Kota unit. I never disassembled neither the helix, sorry propeller, neither the motor.
Inside: you have to check the batteries, probably they are old or damaged. If you are not able dissambly it, probably you have just one battery around 12 V 17-24 Ah 16.5*17.5*12.5 cm ad es. Beghelli 12280 or RS 537-5501. I use a pair of RS 537-7305 like of fiamm(12 v 14AH) in pair. You can use a 12 V 7.2 Ah in a set of three. The trigger don't work good, the reed but the problem is on the magnet, i use a magnet inside the glove on the thumb (ah ah ah ah!). I also check the relay inside the box, because it works and not work, it's a relay commonly used in cars, here in Europe. You can find it at motorshop. 30 A, with fuse if possible.
One thing very important: be sure that the electrical bolts are very tight: the current is high so almost a little gap can produce heat and burn cables, . When i have just buyed and not checked, it appens to me, a cable is burned inside the box of the relay. If you have quatsion ask. A lottle of bubbles. Giorgio