On my proline I had a sealand suction type macerator in the bilge for my fish boxes. It died and I am trying to replace it witha jabsco pump. The problem is I keep blowing the fuse at the switch. I know the new pump draws a lot more amps than the other one. What are my options. There are three wires that go to the pump and two wires off the pump. The sealand also had some sort of float box that the wires went into and then two to the pump. Tried it with the new pump and it still blew the breaker at the switch. Hope I explained it well enough. Thanks all.
Don't know how to say this but here goes. A friend called me once because he had hooked up his deep well pump to his 115v house power and kept blowing the breaker.
I unraveled his interface connection and all three wires were in contact with each other. He had no electrical knowledge and didn't know that they all had to be isolated from one another.
To blow the breaker you have to exceed the amperage it is rated for and incorporate the time delay in that overload. High overloads blow fast and low take longer.
The breaker may be faulty and trip unnecessarily so don't rule that out.
The breaker is to be on the 12v power wire only. The other wire is return for the motor (probably) and the third wire is possibly safety ground.
The switch you refer to is probably a single pole single throw (SPST) switch which supplies or interrupts 12v to the pump as a function of how much water is in the box/bilge. Troubleshooting is a piece of cake.....ohm across the in and out wires (power off) , float down open circuit, float up short circuit.
You need to get the specs on the new pump and see what the starting surge is and running current.
Hopefully the time delay curve in the breaker will tolerate the starting surge.
The running current required by the motor shouldn't be more than probably 50% of the breakers rating. The actual percentage depends upon the wiring insulation and wire temp vs the load. The breaker must break before current through the wire heats the wire enough to melt the insulation. That's usually a large overload (say 200%) for a goodly period.
For exact numbers on breakers and all that the National Electrical Code can give you specifics.
Other possibility is a shorted motor in the pump. Hard to ohm across the power inputs to the motor as the non-rotational dc resistance is quite low.