I have a 1980 Scamp 16-ft with a 6-gal electric Suburban hot water heater. I turned it on and left it on, thinking a thermostat was controlling the temp. After about 30 minutes both hot and cold (yes, cold) were scalding hot. Does it have a thermostat? I used clear plastic lines to replumb bo the hot and cold water lines...should the hot water lines be some other type?
Sounds like it is set to max - you should only be getting a little warm water for the first minute you run the cold water. I have the same set up and my Suburban tank does have a thermostate. Its on the outside of the trailer in the hot water heater box where you fire it up. On mine there is a slider switch - which goes colder/hotter and its located just above the main on/off dial on the same box the dial is located - which on my trailer is a blue dial.
The hose for hot and cold can be clear - mine were replaced not so long ago. Just make sure that you got the plumping hose that is rated and made for hot water - it should say on the outside of the hose what its good for. The person who owned the trailer prior to me had replaced the hot water hose but did not use one rated for hot water - after a time I noted it bulged out and was looking like it was ready to blow apart.