Voltage at engine while cranking F225TXRD

[fairdeal]

I have notes of some voltage measurements I made a while ago -

battery terminals before & during cranking, engine + lug before & during cranking

but I took a few moments today to repeat the engine measurements and video

here's how the meter was connected:

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Here's a screenshot while cranking with the lanyard pulled:



and the video link:

https://vid.me/Z3dWT

[fairdeal]

and then replacing the lanyard and starting normally,
a screenshot just before the engine "caught":



and the video link

https://vid.me/USIif

[fairdeal]

without another to compare it to - AFAIK that's "normal"

cranks fine - always starts fine - usually in less than "one mississippi"

took longer in that video; apparently because I had just been cranking it with the killswitch tripped

[pstephens46]

Wonder what the meter would show if one lead was hooked to positive on battery and other on starter red post? Cranking.....

[fairdeal]

eliminate the ground path - interesting.
Easily done. Will report back...

[panasonic]

You have a DC clamp meter? Would like to see how much amps being drawn from battery on start....

[pstephens46]

eliminate the ground path - interesting.
Easily done. Will report back...

Where did you get your copper clamps, btw? For the meter leads?

[99yam40]

usually copper plated as copper is too soft to make a clamp out of, or some alloy
then if tin plated they do not turn green as bad

[fairdeal]

Wonder what the meter would show if one lead was hooked to positive on battery and other on starter red post? Cranking.....

Ah. I misunderstood -
yes, that would directly indicate the voltage drop due to the cable.

What I did, was connect the voltmeter to the starter red post - and the battery negative:



No surprise, a higher voltage result than yesterday, which measured both ways through the engine battery cables.

I also measured at the battery - between the terminals -
so the battery voltage output drops to 10.8 while cranking

but it appears I'm also losing ~1.1 volts to each side of the engine battery cables

You have a DC clamp meter? Would like to see how much amps being drawn from battery on start....

I would also love to measure that. Have two inductive DC amp meters - but both max at 100. I'm sure its much more.

[oldmako69]

Semi related -

Last fall my Port engine had an intermittent "no-crank" at the turn of the key. Sometimes the starter would engage and sometimes it would not.

Pulled and had the starter tested. Good as new.
Swapped the starter relays. No change.

Dug around in the bilge and found a connector block off to one side. Yam engine leads are only so long and would not reach my Batts. So, the distance difference was "solved" by running long leads from the batteries themselves (POS was from the Batt selector switches) to the connector block, where they were then joined (SS Bolts and Nuts) with the Yam cables.

What kind of condition do you think that these 12 year old connectors were in?
Turns out that I was losing a hell of a lot of current due to corrosion between the lugs at this bilge mounted corrosion collector. I cleaned them, reassembled and slopped Fluid Film all over them. Problem solved.

Two weeks ago the problem returned, but now its the Stbd engine. Pulled and cleaned them again but the problem still persists.

So, I suppose that I need to measure the V drop between the Batts and the connection block. And again between the Batts and the connections on the engines themselves. And / Or, measure the resistance of the Batt cables and see if internal corrosion is stealing my amps.

Plz learn me how to do that on my DVM, as its got about a million settings and I'm dumber than Forrest Gump.

I assume that I'l have to add a long piece of wire to the battery lug to do this. Will that cause inaccurate readings due to voltage drop?

[fairdeal]

Where did you get your copper clamps, btw? For the meter leads?

[99yam40]

Semi related -

Last fall my Port engine had an intermittent "no-crank" at the turn of the key. Sometimes the starter would engage and sometimes it would not.

Pulled and had the starter tested. Good as new.
Swapped the starter relays. No change.

Dug around in the bilge and found a connector block off to one side. Yam engine leads are only so long and would not reach my Batts. So, the distance difference was "solved" by running long leads from the batteries themselves (POS was from the Batt selector switches) to the connector block, where they were then joined (SS Bolts and Nuts) with the Yam cables.

What kind of condition do you think that these 12 year old connectors were in?
Turns out that I was losing a hell of a lot of current due to corrosion between the lugs at this bilge mounted corrosion collector. I cleaned them, reassembled and slopped Fluid Film all over them. Problem solved.

Two weeks ago the problem returned, but now its the Stbd engine. Pulled and cleaned them again but the problem still persists.

So, I suppose that I need to measure the V drop between the Batts and the connection block. And again between the Batts and the connections on the engines themselves. And / Or, measure the resistance of the Batt cables and see if internal corrosion is stealing my amps.

Plz learn me how to do that on my DVM, as its got about a million settings and I'm dumber than Forrest Gump.

I assume that I'l have to add a long piece of wire to the battery lug to do this. Will that cause inaccurate readings due to voltage drop?

if you are looking for resistance use the ohm setting
if looking for voltage you set the meter to DC voltage.

[pstephens46]

Those Yam cables are pretty nice. Compared to some of the junk found at big box stores. I would be careful with the quality.

Always got a laugh when Solo would write about his battery cables that crumbled in his hands....Kmart for sure!

[pstephens46]

I like em big and fat.

[fairdeal]

Direct measurement of voltage drop

OK, with the voltmeter leads
- on the battery positive terminal
- on the engine positive cable lug
while cranking:



so as already indirectly derived, a loss of ~1.15 volts due to the cable
(and another 1.15 lost on the return to ground)

Its the original 2005 Yamaha cable - soldered lugs.
About 3-4 feet longer than it needs to be - excess folded and ziptied above the bilge.

Given that the engine always starts immediately - I'm not motivated to mess with it.
Certainly not to pull it out of the rigging tube to replace or modify it.
And without the proper hydraulic crimper,
I'm not going to attempt to shorten it in situ.

But interesting to know the numbers: that the engine cranks - and starts fine - with 8-8.5 volts at the starter lug.