Lyle,
Most of the boost solenoids that were used on the SMC era coaches stop functioning because of corrosion on the contacts. If you feel the solenoid click when someone activates the switch, you can usually repair it by drilling out the rivets that hold on the top and cleaning the contacts, then reassemble it with small bolts.
If you replace it with a 80 amp solenoid, it will probably not last vey long if it is used very many times as a boost solenoid. When you use it to start the engine from the coach batteries, it will have to carry up to 400 amps, and that will burn up a 80 amp solenoid.
Gerald
