News f2s wrote:

Turning the key, nothing either.

The stereo turns on and plays music, but the marine radio will
not. I
checked all the fuses under the dash and they all seem ok.


I don't know your boat, but my first checks would be:

1. Check and clean *all* high amperage circuit connections -
that includes the earth returns, often forgotten.

2. When you select 'start', listen for the solenoid switch to
click. If it doesn't click, clean *all* the low amperage solenoid
connections, including the earth returns.

3. If these don't work, get your portable multimeter out of the
attic. Lift the positive terminal off the battery and check the
circuit resistance through the starter motor, then through the
solenoid. Both should show just a few ohms. If they don't, there's
a break in the motor/solenoid circuit. If they're OK -

4. Check the resistance through the circuits from the battery
terminals - with the switch made.

After this, you should have narrowed the fault down to either a
line break, or a high resistance joint, and you'd know whether
it's in the solenoid circuit or the starter circuit.

There's one other item to check: many boats run the solenoid current
through a microswitch on the gear shift that ensures that the vessel
is in neutral when starting. This is especially important in a power
boat with large engines! The solenoid current is actually rather high
(20+ Amps?) so a voltage drop is possible. The traditional way of
checking this is to put a screwdriver across the solenoid terminals,
but there are obvious risks to this! (A friend did this by mistake
while under his car, which promptly jumped off the jackstands and ran
him over!) Another way to test might be to jumper at "ignition key"
switch, where a pair of wires could be headed towards the gearshift.

If this is a problem, you can use a small relay (under $10 at Radio
Shack) so that only a tiny current has to make the trip through the
various switches towards the starter. The small relay switches the
solenoid (which is a larger relay) to run the starter.