F50tlrc blowing starter relay

[rodbolt17]

kinda goes back to how far away is the keyswitch?
remember current has to flow and the operating voltage maintained from the power source to the keyswitch and back to the power source.

means if the keyswitch on a 36ft boat is 18 ft from the motor your going to see a 36ft cable run.
as most 50 hp and up F motors use an automotive style starter that needs the solenoid to not only make the contact for the starter motor but the solenoid has to be powerful enough to move and hold the starter drive.

a 26 ft cable run using 16 or 18 Ga wiring would not reliably carry enough current to insure the device worked.

however to operate a small magnetic contactor(relay) that small light weight wire is more than ample.

and that's why most F motors use a start relay as well as a start solenoid.

it simply keeps wire and switch sizes small and light while insuring reliable starter engagement.

and that's why I said if he is burning up relays to check the relay connections and circuits.

if its burning contacts then check the power supply and to the relay and the wiring between the relay and the starter.
if smoking the magnetic coil then check the keyswitch start circuit and relay ground path.

unlike chebbys ferds and caddylacks, mercruiser Volvo, and Yamaha sometimes have NO control on how far away from the starter the keyswitch is.
take a 58' egg harbor with 454 crusaders with V drives and the keyswitch may be 45 cable feet away from the engines.

[99yam40]

good info, thanks to all

Now we just need the OP to tell us what was blowing on his start relays

[Bilge Rat]

Interesting and informative conversation.
Defining and explaining what goes on in a bad connection is a lot harder than finding it.

Thanks for having this conversation. I enjoy learning not just the what but the why. Most people today just want the answer to the problem and never learn anything that will help them in the future.
Thanks

The OP should find his issue with yalls help.

[rodbolt17]

actually finding a bad connection is as simple as a voltage drop test easiest with a DVM but can be done with some analog meters.
my CD77 will drop into the 5v scale and will read in .5 v increments.
most any connection that drops more than .3v can be considered bad.

[Bilge Rat]

A DVM, some jumper leads, and pen/crayon and paper are what i grab for any electrical issue.
Someone needs to write a manual on practical uses of the meter as a basic teaching tool. I learned a lot many years ago by taking a new meter and using it on a 3 phase commercial washers switch gear. when one broke i had a clue of what was going on in there.
I was exposed to electronics by a tech that installed mobile phones that were 50lb Motorola beasts with a mike, speaker, and keypad on the dash. 450meg if i remember right. Times have changed but a good meter and basic skills are still useful.

Voltage, ohms, and voltage drop will same hours of time. Otherwise you are just poking around looking for sparks!

Thanks for your time educating the interested idjits like me.

[rodbolt17]

I was exposed to electronics from about 1976 to about 1987 by working in the auto repair industry and programming,setting up and repairing CNC lathes and mills.
from 1988 to 1995 it was as a firecontrolman in the USN.
went in as E-1 dumb bass ,made E-5 dumb bass in 1991 and was medically retired in 1995.

most folks aint gotta clue about voltage drop and what it means.

basically its potential difference(electrical pressure) between two points.

take the negative battery cable.
its a piece of wire between the negative terminal and the block.
should have roughly o ohms resistance and may actually test that way even though only 1 strand of battery cable is left.

remember its a piece of wire.

now with only 1 strand hanging on in the corroded spot it will ohm out perfect.

however if we place it under a load by operating a device the device most likely will fail to work.

a quick test you ask???
simply place one meter lead on the battery - terminal the other on the block and operate the device.

any bad connections will show up as a resistance and you will read the DROP acrossed that resistance.
if everything is perfect you will see less than .5V.
anything above .7volts means connection issues.

that meter is a techs best friend and for most their worst enemy.
most techs simply have no clue what,why and when to use various tests and meter functions.

but its actually incredibly simple.


FIRST thing is understanding the circuit and why is it designed that way.
if you don't get the first the 2nd though tenth wont matter cause your lost in space and getting the danger will robinson message.

luckily electrons pretty much react like water in a pipe for low voltage DC circuits.

yes my primary NEC 1121 CIWS and I was working on a Harpoon weapon system secondary NEC.

[FabricGATOR]

take the negative battery cable.
its a piece of wire between the negative terminal and the block.
should have roughly o ohms resistance and may actually test that way even though only 1 strand of battery cable is left.


a quick test you ask???
simply place one meter lead on the battery - terminal the other on the block and operate the device.

any bad connections will show up as a resistance and you will read the DROP acrossed that resistance.
if everything is perfect you will see less than .5V.
anything above .7volts means connection issues.

Great brain nugget, thank you.

I want to better understand this troubleshooting method, so I ask...
Scenario: Suspected bad battery ground wire. Hanging on by single strand.
TEST: check resistance from negative battery post to ground spot on engine block.
Finding: Initial, low resistance due to good (single strand) connection.
TEST: Engage tilt motor or starter while continue to monitor resistance
Finding: Resistance indication will rise while load is engaged due to higher current flow.
Is this correct? I'm not questioning the lesson, I just want to confirm my understanding. This is yet another way to utilize the meter in troubleshooting that I had never been exposed to or taught before. Thank you.

[rodbolt17]

NO NO NO

NEVA EVA EVAAAAA test a LIVE circuit when on Ohms or resistance settings.

some meters will simply pop the fuse others will die a violent death involving smoke.

once your done with checking circuit resistance and you wish to move on to voltage drop testing reset the meter to the anticipated voltage range.


+-----------b----------c---------d----------e-----Starter.
diagram

what the electrons see +---------------------------------starter.

from + to the starter terminal you see 4 connection points.
in a perfect world electron flow would be uninhibited.
there would be NO potential difference between +and the starter.

now toss in a 10 K resistance on point b.with the meter lead on + and the other on b you would see the potential difference represented by a voltage on the meter.
now leave on lead on + and the other to point d,
if point d has 5 K resistance you will see an additional voltage(potential difference) and so on and so on.

all that voltage drop test is doing is looking for a potential(electrical pressure) difference between point a and the starter.
in a perfect world with perfect connection there would be NO difference from one end of the wire to the other.

but now we are dealing with a battery terminal at +.
two battery cable ends at b,2 at c two at d and one more at the starter.
every connection point has a potential for a less than perfect connection.
less than perfect equals a resistor.
resistor hamper current flow and thus there is a potential(voltage) difference acrossed that resistor.

Ohms law works well but also study Kirchoff's laws on current and voltage.

once you understand why that meter works and you look at the diagram you will find DC electrical testing is rather simple.

[FabricGATOR]

Oopsie

In retrospect, I see that the starter current would want to take that ground path through my meter in parallel.

I am glad I asked for clarification, while open to new technique, I didn't fully grasp what you were originally saying. I'd like to think that I would hesitate in practical application, but I may have smoked a fuse if not my Fluke.

At times I wish I had a crystal in my navel. Then when I had my head so far up my rear end, at least I could look out and see what direction I was heading.

Thank you rodbolt17.

[boscoe99]

Here is a graphic example of what is being discussed relative to voltage drop testing. Starter motor would be energized approximately 5 seconds for the test.

These diagrams do not depict battery switches, extended battery cables, use of battery posts, etc., etc. All of which would be tested (and could be problematic) if installed.

[FabricGATOR]

Gotcha

Thank you Boscoe99

A picture is worth a thousand words.

So that would show my complete conductor side resistance, then I could repeat the testing from point to point along the path (say from battery to terminal, terminal to relay, relay to starter) until I found a section that had increased voltage through my meter. That would be my problem area. I think I understand, I reiterate for my own clarity and the benefit of others.

Ignorance is not always bliss... at least not in my case.

[boscoe99]

To be technically correct, it will show the voltage drop, not the resistance.

But yes, excessive resistance can lead to excessive voltage drop.

[FabricGATOR]

Roger, wilco.
Thank you.