Dead Solenoid?

Apr 8, 2010
1,606
Frers 33 41426 Westport, CT
went down to the boat a few days ago for the first time in just shy of 2 week2 (too much time racing on OPB, not enough time cruising on mine!), found my batteries were at 0.2v... I had left nothing on, and I have a small solar panel which usually does a good job keeping everything topped off and at float charge, so clearly something drained them:confused:.

I checked the bilge pump, being one of two things that had power (the other being the memory circuit on the stereo) and it was ok, nothing appeared abnormal.

Some further testing with the multimeter while pulling wires off the main buss bar revealed that I appeared to have an open short on somewhere downstream of the engine battery cable, and I'm pretty sure I have traced it down to the starter solenoid on the outboard.

When I disconnect the battery cable from the buss bar and the ignition wire fuse from the solenoid, thus leaving the solenoid completely disconnected from on positive side, and then test from the positive post on the solenoid to the engine block where the ground cable is attached, I read 0 ohms of resistance. This indicates to me it's shorted internally (and though there is no evidence of wires having gotten hot or melted insulation anywhere, I'm still lucky to have not had a fire).

Before I order a $70 solenoid, can anyone confirm that it sounds like a bad solenoid, or suggest anything else I should investigate before ordering parts?
 

walt

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Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
My boat sits for months at a time with a similar setup. I have a 10 watt panel that just maintains the batteries and I turn everything off except the charge controller connected to the battery. Normally works well.

I have a power switch on the outboard so that I can completely disconnect it from the battery and always turn this switch off when I leave the boat for an extended time.

But one time I left the switch on so the outboard was connected to the batteries. I came back to the boat after a hot spell (ie, the summer in Lake Havasu Az) and the battery was about dead.

I never could measure anything that caused the problem but I suspect it was somehow the outboard and it also seemed to be heat related.. All I do now is just make sure the outboard is disconnected (by a power switch) any time I leave the boat for an extended time. I havent had a problem again doing this and everything about the outboard seems to work just fine.

and then test from the positive post on the solenoid to the engine block
where the ground cable is attached, I read 0 ohms of resistance. This indicates
to me it's shorted internally (and though there is no evidence of wires having
gotten hot or melted insulation anywhere,
Sounds not right but solenoids usually fail closed when they are already closed (sort of welding the contacts together). If the starter soleniod was open when you left it.. odd that it would be shorted now.
 
Apr 8, 2010
1,606
Frers 33 41426 Westport, CT
Sounds not right but solenoids usually fail closed when they are already closed (sort of welding the contacts together). If the starter soleniod was open when you left it.. odd that it would be shorted now.
Yeah, I agree that part is the weirdest, but maybe it is stuck closed just enough to allow a trickle of current through? wouldn't take too much to be more than my panel outputs (1.2A at peak sun), and even a half amp/hr net drain would kill the batteries in a week and a half, probably faster considering the solar wouldn't be doing anything to offset at night...

It has sat essentially in this same config with the battery cable to the starter solenoid attached and powered for the entirety of the 6 years I have owned the boat and never once had an issue before. While it was pretty hot over the last 2 weeks, I don't see what temperature would have to do with it, or why that would cause a short in the solenoid??
 
Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
Coupla notes, Brian.. Make sure your ohmmeter is set so it can read low ohms.. like 3-4.. not set to the 20K ohm scale, or higher.. The other one is did you try taking the readings both ways, I mean take a reading then reverse the wires (red/black) at the engine and read again. sometimes you could have a diode in the engine charger circuit that might conduct with the power from the voltmeter and give a strange reading. You can disconnect all hot wires from the solenoid and check it pretty quickly. Disconnect the big incoming hot and unplug the little start button connection. Read across the big terminals and it should read infinity (open) .. read from the little wire terminal on the solenoid to ground and it should read a few ohms, like 10 or there abouts (but it could be some more or half that, just not many.. If you see those results, the solenoid is good..
I'd suspect something like a bad diode in the engine charger or the bilge pump .. especially if you see no evidence of heat on the solenoid case or the starter motor itself. Diesel inboards have a history of having rain or sea water short the start pushbutton and burn out the starter sometimes while no one is there if things are left connected..
 
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
if you measured from solenoid control post to ground you should get no resistance. the solenoid is not the switch it is just a coil of wire. the switch is the starter button or ignition switch "start" position. The way it works is the power is normally off till you hit the start button. current then flows to the solenoid, through the coil of wire making a magnetic field. The magnetic field pulls an iron core with a high power switch on the end into the coil. The high power switch completes the circuit between the big battery cable on the solenoid and the starter motor windings.
Also, if you test between the two big cable terminals you should get an open (infinite resistance) circuit
 
Apr 8, 2010
1,606
Frers 33 41426 Westport, CT
Coupla notes, Brian.. Make sure your ohmmeter is set so it can read low ohms.. like 3-4.. not set to the 20K ohm scale, or higher.. The other one is did you try taking the readings both ways, I mean take a reading then reverse the wires (red/black) at the engine and read again. sometimes you could have a diode in the engine charger circuit that might conduct with the power from the voltmeter and give a strange reading. You can disconnect all hot wires from the solenoid and check it pretty quickly. Disconnect the big incoming hot and unplug the little start button connection. Read across the big terminals and it should read infinity (open) .. read from the little wire terminal on the solenoid to ground and it should read a few ohms, like 10 or there abouts (but it could be some more or half that, just not many.. If you see those results, the solenoid is good..
I'd suspect something like a bad diode in the engine charger or the bilge pump .. especially if you see no evidence of heat on the solenoid case or the starter motor itself. Diesel inboards have a history of having rain or sea water short the start pushbutton and burn out the starter sometimes while no one is there if things are left connected..
Good suggestion, that little voice in my head told me there was potentially something I was missing and hadn't tested yet, this is it (and to re-supply the rum :doh:). I'll test it tonight after I get back from racing.

Not that it makes any difference for the solenoid testing procedure, but it's an outboard not a diesel inboard.
 
Apr 8, 2010
1,606
Frers 33 41426 Westport, CT
Also, if you test between the two big cable terminals you should get an open (infinite resistance) circuit
that is precicely what I was testing, the big + battery cable connection point on the solenoid and the big - battery cable connection point on the engine block, and they showed closed (zero resistance) circuit.
 
Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
Understood it was an outboard, but the problem could happen the same way.. butI have not heard of an outboard doing that..
I would be surprised if it had shorted and not smoked something.. not saying it can't happen.. just saying surprised.. Happy hunting !
 
Apr 8, 2010
1,606
Frers 33 41426 Westport, CT
Understood it was an outboard, but the problem could happen the same way.. butI have not heard of an outboard doing that..
I would be surprised if it had shorted and not smoked something.. not saying it can't happen.. just saying surprised.. Happy hunting !
thanks, I can only think of humidity being a cause. I added a new blue sea systems engine cover this year to protect the paint on the "new" engine cover so the paint and decals don't fade and look so bad as the old one, so maybe that's trapping more humidity / moisture?
 
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
OK
A common problem. The contacts get corroded over time and with all the amps welds itself to the cable terminal posts on the inside causing a short circuit.
Try this take a hammer and using your best engineering look, impact modulate the terminals end of the solenoid.
Note: if you break the solenoid with the hammer you did not preform impact modulation you just hit it too hard, there is no implied or actual warranty with this advice. ;-)
 
Apr 8, 2010
1,606
Frers 33 41426 Westport, CT
OK
A common problem. The contacts get corroded over time and with all the amps welds itself to the cable terminal posts on the inside causing a short circuit.
Try this take a hammer and using your best engineering look, impact modulate the terminals end of the solenoid.
Note: if you break the solenoid with the hammer you did not preform impact modulation you just hit it too hard, there is no implied or actual warranty with this advice. ;-)
didn't end up making it down to the marina last night as I stayed for dinner and left the club at 10pm (I get a slip at the yacht club next year:dance:) but I will attempt to modulate the contacts into proper position through the use of carefully applied shock forces with a precision metal tool, aka hammer, and see if the circuit remains open after that. If I can confirm that appears to be the problem, and even if I remedy it, then I'll still replace the solenoid, but at least I have confirmed that's the only problem, and will be able to temporarily use it in the mean time.
 
Apr 8, 2010
1,606
Frers 33 41426 Westport, CT
Precision modulation via blunt steel impact seems to have (temporarily at least) solved the problem. I pulled the solenoid and confirmed zero ohms of resistance between the always hot battery cable post and the case where it bolts to the engine block (and tested both directions to verify it wasn't a diode). Some love taps with the hammer on both the top and bottom and like magic, now it's an open circuit as it should be. I'll get a new one ordered because it's probably going to happen again sooner than later, but at least I'm operational for the weekend :)