Replacement Trackmaster Motor

Is it a case of the motor being 'too fast' or simply the gearing that is a problem? If you've been trying the Tamiya motors for example they have specs for the RPM etc... I believe. If its just standard 'can' motors you've been picking up do they maybe need a capacitor or something to change their behaviour?

Not having any Trackmaster I don't know about the internals, maybe someone more familiar with them here would know??

To add to Super's suggestion of sealing the motors, I'm sure you could use some form of rubber or maybe hot glue to seal any joints on the metal work, but if you do don't forget to put some grease around the axle entry point into the can or else water may ingress there and you can't really put any sealant there.

Another thing I would suggest (based on recent experience with a mobile phone ) is if you do get one 'dunked' before you try to run it again and potentially short the motor put the model in a sealed plastic box with some raw rice. Leave it for a few days and it should remove any fluid from the motor and it may then work perfectly fine again - it worked for a mobile which took a little trip down a loo