quick starter question

cschaul1

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May 10, 2006
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just wondering if a voltage drop from the battery to the starter terminal can be caused by a bad starter? more specifically, i have a reading of 6 volts at the starter and thought it may be because the starter itself is partially seized or bad, is that possible? or would a bad starter still read 12ish volts at the terminal? thanks
 

Don S

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Re: quick starter question

Could be a bad starter, a bad battery cable (either positive or negative), a bad battery, or even a tight engine or drive.<br />Check your connections. Clean and shiny, and don't forget tight. Wingnuts shouldn't be allowed on batteries, they cause more problems than they cure.<br />Get your battery load tested.<br />Pull the starter and have it checked out.<br />If all is well, pull the drive and see how it cranks, and pull the spark plugs from the engine and check for rust or other indications of water.<br /><br />Thought this was going to be easy didn't you?
 

cschaul1

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Re: quick starter question

i thought it would be easier than it has been so far...you are correct on that one! i am going to replace the cables as they are pretty old looking and have been getting hot when i try to start the boat. i am going to take the starter out to a shop to have them test it. i am hoping that it is just the cables or starter, if it is the outdrive then my vessel is sunk. have a good one, thanKS for the help
 

cschaul1

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Re: quick starter question

i thought it would be easier than it has been so far...you are correct on that one! i am going to replace the cables as they are pretty old looking and have been getting hot when i try to start the boat. i am going to take the starter out to a shop to have them test it. i am hoping that it is just the cables or starter, if it is the outdrive then my vessel is sunk. have a good one, thanks for the help
 

cschaul1

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Re: quick starter question

i thought it would be easier than it has been so far...you are correct on that one! i am going to replace the cables as they are pretty old looking and have been getting hot when i try to start the boat. i am going to take the starter out to a shop to have them test it. i am hoping that it is just the cables or starter, if it is the outdrive then my vessel is sunk. have a good one, thanks for the help
 

I/O WALDO

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Re: quick starter question

Or too much load(starter/tight engine)if the cables r getting hot and knott the cable ends.
 

cschaul1

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Re: quick starter question

if the starter is worn out would that create too much load? before everyone mentioned cables i had thought that it was the starter being bad which caused the cables to warm because the lack of free movement of the internal parts of it created some resistance which held up the power in the cables creating the warmer temperatures. is that the correct logic? i will hopefully know on thurs when i can get the starter to a starter shop. thanks<br />corey
 

jtexas

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Re: quick starter question

No starter will start with only six volts. You should get approximately the same voltage across the starter as you get across the battery terminals - if you only have 6v at the starter, then you've got 10 times more resistance in your battery cables than you should, or else the battery's shot.<br /><br />A worn out starter can heat up the cables, but it's because there's more power flowing through them. The starter itself would also get hot in this case.
 

cschaul1

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Re: quick starter question

interesting, could the solenoid be bad as well if, when the cable going to the starter is disconnected, i get 12volts coming through it, and when the starter is connected i only get 6 volts leaving the solenoid? what i am thinking is that it is possibly just the short 1-1.5 foot cable that runs from the solenoid to the starter, along with the solenoid that needs replacing.
 

jtexas

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Re: quick starter question

1. Voltage from solenoid battery input terminal to ground should be 12.6v (battery open circuit voltage).<br />2. Solenoid starter output terminal to ground should be 12v (at least) when the key is turned to "start".<br /><br />If 1 is true and 2 is false then the solenoid must be bad (with a known good battery).<br /><br />This is my theory (and I'm no expert) - the solenoid is weak and adding resistance to the battery-solenoid-starter-battery circuit. Without the starter, you'd measure the full battery voltage at the solenoid output regardless of its resistance. The voltage drop across the solenoid (from battery input terminal to starter output) with the starter engaged should be zero (or close to it), but I bet you get about 6 volts.<br /><br />I guess there's a chance something's wrong with the battery - have you checked it with a hydrometer?
 

bruceb58

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Re: quick starter question

Measure these 4 points while you are cranking the starter<br /><br />1) Battery<br />2) Input to Solenoid<br />3) Output of solenoid<br />4) Starter Input<br /><br />The highest voltage will of course be at the battery. Every connection down the line shouldn't drop more than 0.5V or so.<br /><br />If your battery is indeed dropping down to 6V, it is either your battery is bad or you are drawing so mauch current from a bad starter that it is causing the extra drop. Batteries have internal resistance. It may be very small but if your drawing 600A, a small resistance produces large voltage drops.
 

jtexas

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Re: quick starter question

bruce - my knowlege of DC electrical is all self-taught, so if you don't mind I could use a little help understanding the theory here...my understanding: if the battery is putting 12 volts into the circuit, then the total voltage drop across all the components (wiring, solenoid, starter motor) will be 12. If you only measure 6 across the starter, then something else in the circuit has too much resistance.<br /><br />But you're saying that the voltage drop across a stalled starter will be reduced?<br /><br />cschaul, hope you don't mind me tossing a theoretical question into your thread - I'd hate to steer ya wrong.<br /><br />thanks!
 

bruceb58

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Re: quick starter question

I * R = V This is Ohms Law.<br /><br />I = Current<br />R = Resistance<br />V = Voltage<br /><br />If you measure 12.5 V at the battery and then measure 12.0 V at the starter solenoid, you will have a 0.5V drop. <br /><br />The resistance of a cable can be calculated from tables. That would leave you with the amount of current. <br /><br />The best way of running tests for this problem would be to have a clamp on current probe. I don't own one of these.<br /><br /><br />Regarding your comment that the total drop across all components...it is true. That is basically the voltage betweem your battery voltage and ground. By measuring the voltage at each point, you can subtract the two points to determine the voltage drop between those two points. Another way of getting that value would be to just measure those two points directly. <br /><br />If there are 6 volts at the starter, you know one of 3 variables of the ohms law equation. Either the resistance is high or the current is high. I wanted cschaul to make measurements to see if a lot of the voltage drop appeared in one portion of his circuit.
 

cschaul1

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Re: quick starter question

hey guys thanks for the insightful responses. as i said earlier i had 12+ volts at the batter and at the (entering the solenoid) and exiting the solenoiod (leaving it heading to the starter motor itself) was 4-7 volts. this voltage drop was only when the starter motor cable was attached to the solenoid and the ignition switch was turned to start. now, when the cable to the starter is unattached to the solenoid it reads 12 exiting the solenoid. i took the starter to a starter shop and they looked at it, there was a lot of what seemed to be deterioration with the inside of the starter. for all i know the thing could be as old as the boat itself. anyways i bit the bullet and had the shop rebuild it. it will be done tomorrow afternoon and after work i will check out to see if it works. if it doesnt i will replace the cables and solenoid. i am truly interested to see what happens tomorrow afternoon and i will post the results here when i find out. thanks to everyone who has helped me out here.
 

Don S

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Re: quick starter question

I don't have a clue as to where or how you are measuring your volts, it really doesn't matter.<br />If you have a good battery that passes a load test and is the proper size for a boat engine.<br />The cables (Both positive and negative) are properly sized for length and load, and the ends are crimped and soldered, not corroded in any way and the connections are CLEAN and TIGHT, and your cables are still getting warm, then you have a starter dragging because it's worn out or corroded, or your engine or drive is siezing up on you.
 
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