8.1 Solenoid question

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by SeadawgVB, Dec 4, 2017.

  1. SeadawgVB

    SeadawgVB Member

    161
    Jul 8, 2013
    Tidewater Virginia
    '03 Sundancer 360
    Twin 8.1s with V-drives
    Since I've had my 360DA I've had intermittent starting problems. Even seen on the sea trial. The previous owners mechanic "addressed" issue, by some random thing that really didn't do anything. At first I thought it was the neutral switch, so I wasn't overly concerned, but the last couple of outings it has seemed to have gotten a little worse. It is always the first start of the day, once it has fired, the rest of the weekend is no problem.
    Here's the deal: (I'm already expecting a corroded ground somewhere, but I'm hoping someone here can point me in the right direction.)

    Sometimes it's the starboard, sometimes it's the port. When I push the start switch, I hear a solenoid click but nothing happens. Yesterday it was the starboard. I hear the click but no spinning starter. I hold the start switch down and move the shift lever for and aft a touch and can hear the solenoid click on and off so I am fairly confident it is not the neutral switch.

    I got down in the engine room and have my wife cycle the switch and determine it is the slave solenoid (up on the top of the engine) that is clicking. Usually I turn everything off (key, breaker down in the cabin), turn every thing back on, mash the starter switch a few times and boom, starts right up.

    If you read thru all that, you finally made it to THE QUESTIONS: How is that slave switch related to the actual starter solenoid? (connected in series?) What is the actual starting sequence of events? Does the slave solenoid trigger a solenoid at the starter. Since it seems like some possible corrosion, where is the most likely area to look? Starter battery connections? (A brief glance yesterday, looked fairly clean, my engine room is fairly clean as well.)

    PS, It did finally start up yesterday, when the starter does turn, it cranks with authority and spins the motor quickly.
     
    Last edited: Dec 4, 2017
  2. hottoddie

    hottoddie Well-Known Member

    Jan 11, 2012
    Boston/Cape Cod
    1986 Sea Ray 390 Express
    Garmin 4212 Chartplotter
    Garmin 24 HD Radar
    Garmin GSD 22 Sounder
    Garm
    454 Crusaders
    Probably a good idea to start with cleaning all the connections in the circuit. Battery terminals, cable connections at the slave solenoid and starter. Remove and clean with small wire brush or fine sandpaper and reassemble using dialectric grease. Do the same with the ground connections were the battery cables attach to the engine block. Don't assume the are good because they look clean.
     
  3. Jimmy Buoy

    Jimmy Buoy Active Member

    Dec 3, 2008
    Sarnia, Ontario, Canada
    340 Amberjack
    twin 8.1S 370 Hp + 4.5 Westerbeke Genset
    Had a similar issue 8yrs ago but only with one engine. Ended up being some corrosion on the engine block ground (as already mentioned). Once cleaned and reinstalled no more issues.
     
  4. SeadawgVB

    SeadawgVB Member

    161
    Jul 8, 2013
    Tidewater Virginia
    '03 Sundancer 360
    Twin 8.1s with V-drives
    Bad grounds seem to be the hardest things to track down. I had a '66 Chevelle that I had replaced, starters, generators, voltage regulators, batteries (luckily it was easy to push start by myself!). It wasn't until I decided to replace the battery cables that I found a huge buildup of crust / rust between the negative lead and the block. The crust would allow enough voltage thru to allow ALL the lights to light up bright, until you turned the key and everything would go dark. If I recall, I think I once saw sparks fly from that connection while I had someone turn the key at night. Sparks in an engine compartment..... hmmm.....
     
  5. SeadawgVB

    SeadawgVB Member

    161
    Jul 8, 2013
    Tidewater Virginia
    '03 Sundancer 360
    Twin 8.1s with V-drives
    I'm gonna take a closer look at my connections this weekend. (Closer meaning with wrenches and wire brushes in hand.)
    My question to you is the statement concerning dielectric grease. Is that for use as a corrosion inhibitor? Is there a preferred type for the marine environment, or kind of like any type or silicon grease?
     
  6. hottoddie

    hottoddie Well-Known Member

    Jan 11, 2012
    Boston/Cape Cod
    1986 Sea Ray 390 Express
    Garmin 4212 Chartplotter
    Garmin 24 HD Radar
    Garmin GSD 22 Sounder
    Garm
    454 Crusaders
    As long as the grease says "dialectric" in the description it would be fine. Most greases will act as an insulator, the last think you want to use on an electric circuit.
     
  7. Bt Doctur

    Bt Doctur Well-Known Member

    Aug 21, 2010
    New Jersey
    Ex SRV 240 Weekender twin
    in between
    If you hear the slave clicking the wiring is ok, What you have is a bad slave relay. The internal contacts are bad. If it happens again short the 2 large lugs, this should activate the starters solenoid and starter.
    Why is it there, because the wiring it too small of a gauge to go from the key directly to the starters solenoid,
     
  8. SeadawgVB

    SeadawgVB Member

    161
    Jul 8, 2013
    Tidewater Virginia
    '03 Sundancer 360
    Twin 8.1s with V-drives
    Yep, I understand the relay concept, same thing for these modern High Intensity headlights and horns on cars. I guess my "WHY" question is rooted in my automotive repair experience. Is there a slave relay (which I have located) AND also a primary solenoid inside the starter near the bendix (do they even still have bendix?). My mind thinks there are two, I'm guessing that would make it so the positive battery lead to the starter would only be "hot" during a starting sequence.

    SO, at 10-15 dollars for a replacement slave solenoid (unless I buy it from Mercury), I'll probably just swap 'em out.
     
  9. Bt Doctur

    Bt Doctur Well-Known Member

    Aug 21, 2010
    New Jersey
    Ex SRV 240 Weekender twin
    in between
    The main post on the starter is always HOT, its where you get all your ships power from. The Red wire is the feed to the 50A circuit breaker button
     
  10. outlaw32

    outlaw32 Member SILVER Sponsor

    71
    Mar 15, 2014
    St Petersburg Fl
    340
    496 V drives
    I had the same issue and it always failed at the worst time. I search and search and finely found a broken wire that was only making contact part of the time. on front left side of motor there is a red push button reset there was a wire that was barely connected. I got lucky hit it and it fell off. Good luck these are hard to find. Also when this happen to be I could still jump starter and motor would start. just would not start at helm.
     
  11. MickT

    MickT Member

    70
    Aug 5, 2016
    australia - newcastle
    2006 sundancer 300
    twin mercruiser 5.0 mpi w/bravo III
    D
    dialectric means non conducting, ie, insulating....which is exactly what you want.... If you use a conductive grease you make an electrical short circuit...

    Almost any spray on grease will work here, like "corrosionX", lps3 even a small paintbrush and Vaseline if you're desperate
     
  12. SeadawgVB

    SeadawgVB Member

    161
    Jul 8, 2013
    Tidewater Virginia
    '03 Sundancer 360
    Twin 8.1s with V-drives
    Follow up: Swapped out the slave solenoids and boom... starts right up. I also got a little bit more of an understanding of how it works; The big heavy gauge wires only go to the solenoid on the starter. The slave solenoid is used as a relay from the switch on the dash, to energize the starter's solenoid.

    Still don't understand the why. The slave solenoid is farther from the dash than the starter's solenoid. The only thing I can think of for the why is that allows for the big circuit breaker to be between the slave and the master solenoid....
     

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