Where would the starter relay be located?

[pstephens46]

just to see initially what the meter will read, I connected battery +terminal to the #1 pole on battery switch, reads -.35. If I now turn selector to position 1 on battery switch, jumps to @-9.35. Is it reading the 4ft of battery cable at -9.35 or picking up the issue downstream somewhere with selector set to batt one? Just curious? I am making some leads to start at engine..Thanks for your help!

[rodbolt17]

jumper leads.
can buy them at radio shack or make it with a length of about 16ga wire and two alligator clips.

[pstephens46]

thanks, guess I need some extended meter leads to reach from one end to other.

[boscoe99]

Checked voltage at starter motor, 12.8 but have not checked during cranking. Other electrical items working, pumps, horn, lights,

And that is precisely where the voltage is needed. Does not matter the voltage if nothing is happening. What counts is can the battery provide the starting current and the needed voltage at the same time.

Think of it like a hose pipe. There is a nozzle at the end of the pipe that is closed. The tap at the house is barely turned on. The pressure in the hose pipe will rise to whatever the house pressure is. Now open the nozzle. The pressure is suddenly lost and the water just trickles out. Not enough water to do anything with.

The tap being barely turned on is a restriction. Similar to the restriction in a faulty wire that prevents current flow. Open the tap and now there will be plenty of pressure at the nozzle. Fix the wire problem and there will be plenty of electrical pressure (voltage) at the end of the wire when the starter motor is engaged.

[rodbolt17]

ok
you don't understand how to use that meter.
its very simple.

your looking for a voltage DROP not battery voltage.

at the + battery TERMINAL not cable attach one lead using the DC scale. the other lead will go to the + terminal on the starter again the stud not the cable end.
turn on the key, you should see less than .5V,turn the key to start,should still see less than .7v.

now using the same autoranging DC volt scale attach one lead to the - stud at the battery the other to a good block ground.
turn on the key, you should see less than .5 V try starting it and you should still read less than .5v.

if the + wire reads more than .7V start backing up with the lead that was on the starter battery terminal IE battery switch's and such until it reads less than .7 while loaded.

if the - cable reads more than .5V start backing down the - cable looking for junctions and splices that may have failed.

what we are doing is finding the voltage DROP acrossed a resistance.

take the ground wire and visualize the circuit, barring any terminal junctions it is a straight piece of wire from point a (battery stud) to point B the ground wire attachment at the block.
the only resistance in a perfect circuit would be the resistance of the copper,very low.

now when we operate,or try to, the circuit we are using the electrical pressure,measured in volts, to force electrons(amps) down the wire.
if all is perfect the pressure drop from a to b will be a minimal loss maybe .5V or less.
now if we have a bad spot in the cable(a resistance) we may drop 5-8 or more volts ACROSS that resistor.

loose corroded cable to terminal connections can act as a resistor as can bad cables,bad cable to cable end or any junctions between point a and b.

[pstephens46]

yes digital meter

[pstephens46]

Checked voltage at starter motor, 12.8 but have not checked during cranking. Other electrical items working, pumps, horn, lights,

[rodbolt17]

not confusing at all.
most likely bad battery cable connections or someone left a wire off the battery.
do you have a digital voltmeter?
but it is NOT a starter relay issue,yet.

[pstephens46]

Cranking issues. Batteries strong, 12.8 volts both with meter. Voltage on yamaha guages 7-8? Huge loss somewhere? boat will not crank. Started having issues few months ago. Do relays die slowly? Something seems to. Trim not getting proper voltage either, that is confusing

[rodbolt17]

on the engine.
remove the 3 screws securing the electrical panal.
look down low at the square box with the brown and red wires.
why you ask ?
or as the Japanese engineers would say.
why you need to know?

[pstephens46]

I have a 2005 Century with a 2004 F150TXRD. I am trying to find starter relay. On engine or boat? Thanks