For the clicks, I would look for either a relay, or a pump. Sometimes a water pump which has a very small water leak will give a series of clicks.
Many electric fuel pumps also use a selonid for the pump to move a diaphram.
7 Volts didn't do that battery any good. You might consider either monitering the batteries on a very regular basis--as well as turning the batteries off with a switch or circuit breaker when not using the boat. You can put an ampmeter in series with the battery positive cable and find out how much current draw there is.
I would be a little nervous about taking any water from the turbo cooling--and consider moving the heat source for the cabin heating system to another location....An over heated turbo can be a major and expensive problem. I don't think that the C Rangers have a pyrometer, but it might be a good idea to put one in. This will measure the temp of the exhaust gas (and if you put it after the turbo, it will also give an indication of the turbo cooling). The insertion of the pyrometer before the turbo will also give very good information. The pyrometer might be a good idea if you are spinning the engine up to get semi planning speeds, which puts much more stress on the engine.