Not sure if anyone is still looking at this thread but here goes. I brought my three Nikko subs out of retirement and tested them, one old yellow Ocean Explorer and two black Sea Wolf subs. All three sank in the bathtub, one very quickly, the other two after a couple of minutes. Only one had motors working, the other two appeared seized through lack of use. I have stripped all three subs, dried them out, sprayed WD40, dried in the sun, and so far have myself two working subs in that the motors and mechanisms now turn. I haven't tested them in the water yet as there is still the business of water getting in somewhere. I can't see any obvious cracks and the round seal for the dive propellor housing looks fine. Would it help to ensure a seal to put vaseline jelly on the seal, or would that damage the rubber? The big rubber cap that goes in front of the battery compartment looks intact for all three - if this is where the water is getting in, how can you tell? It seems a tight fit to get the front part of the sub onto the seal.

Putting everything back together was straightforward except for the dive propellor assembly. Does anyone have instructions and/or a diagram to help me with that bit please?