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Mercruiser 4.3L V6 engine WEIRD starting problem (HELP)

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  • Mercruiser 4.3L V6 engine WEIRD starting problem (HELP)

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  • #2
    Re: Mercruiser 4.3L V6 engine WEIRD starting problem (HELP)

    A 550 CCA battery should turn that motor fine. How are the battery cables and ends? Maybe put some jumpers from the battery to the block and starter to see how it spins then. Those cables aren't too much money, you might just do them as a guess.
    If the cables are good, it could be mis timed, or the timing chain could have jumped a tooth. Is it definitely in neutral?
    Try spinning it over with the spark plugs out.
    How does the engine oil look?
    87 Formula F223LS, 97 Alpha Gen II, 97 Thunderbolt V Ignition, 2016 383 Stroker
    Lake Winnipesaukee, NH

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    • #3
      Re: Mercruiser 4.3L V6 engine WEIRD starting problem (HELP)

      Well I can't speak for electrical issues on boats but I can speak to what I experienced less than a month ago with my car. I had to pull the transmission and when I put it back I forgot to bolt back in a major ground strap that powered the alternator, starter, and who knows what else. The vehicle made it 3 miles before the battery completely drained, since that was all that was powering the car.

      You mentioned they just rebuilt the engine, so in the process they had to unhook the wiring harness completely. Could it be they didn't hook up a ground properly? I'd sniff around the wiring just to be sure.

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      • #4
        Re: Mercruiser 4.3L V6 engine WEIRD starting problem (HELP)

        Like NHGUY said, I would suspect cables. EVEN if the connections are clean and shiny, they may be corroded UNDER the crimped on connectors. I chased that gremlin a few years back. Its easy and cheap to rule that out. Get some new crimp on connectors from the auto parts store, cut off the old connectors, and crimp on the new ones. Then cross fingers ...
        86 THUNDERCRAFT LEGACY 18 FT MERCRUISER 4.3 2 BBL 185 HP ALPHA 1 GET IN, SIT DOWN, SHUT UP, HOLD ON !!! TOW RIG 01 CHEVY SILVERADO STD CAB LONG BOX 4X4 5.3 Z71
        sigpic
        GO NAVY!!! USS MERRILL DD 976- SPRUANCE CLASS DESTROYER- ONBOARD 81-85 INTERIOR COMMUNICATION ELECTRICIAN PO 3RD CLASS- TEST SHIP FOR THE TOMAHAWK CRUISE MISSILE. NAS KEFLAVIK ICELAND 86-87

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        • #5
          Re: Mercruiser 4.3L V6 engine WEIRD starting problem (HELP)

          My 96 4.3 does that now, but with a battery charge I can get it spinning over fast enough to fire the engine. It is likely cables. At first I thought it was the starter, but cleaning of the cables helped, although I need to do some more cleaning or replacement of the cables. One of my planned winter repairs.
          I might try a shim on the starter to give it just a little space between the gears of the flywheel also.

          Chris
          1996 Rinker Flotilla, 4.3, 1998 Seadoo GSX Limited, 1995 Hydra 24' Pontoon, 70hp Force, 1995 16' Alumacraft Jon boat, 25hp 'Rude, 1968 Fibra with Volvo stern drive, and various other boats used for parts.

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          • #6
            Re: Mercruiser 4.3L V6 engine WEIRD starting problem (HELP)

            I'll assume you already cleaned the positive and negative cables at both ends since you've had them off the battery and starter. Someone else just suggested the main ground cable where it attaches to the block, so you did that too. If that didn't fix the problem, start isolating the issue with a volt meter and an apprentice.

            Make sure the battery is charged overnight before getting started. That should take it to around 13 volts before you turn anything on that uses the battery. Attach your volt meter negative to the case of the starter and the positive to the copper stud the battery cable attaches to. Have the apprentice start cranking while you watch the meter. While cranking (or attempting to crank) the voltage should be somewhere in the range of 8-10 volts. If it's still up around 12V the starter isn't doing it's job. If it's less than 8V you have a problem in the circuit.

            Starters rarely fail like that, so I'll assume you have too low a voltage and move on to isolate where the voltage is dropping. A wire that is doing it's job will have little or no measurable voltage measure between the ends. If the wire is bad or a connection at the end is bad, a voltage shows up just like water pressure in a stopped up pipe. In the following checks, there should be little or no voltage measured. A measurement over a volt means a problem.

            To eliminate the ground as an issue, connect the negative lead of the meter to the negative battery terminal and the positive lead to the case of the starter. When your apprentice cranks, there should be less than 1 volt measured. If it's more than that, start working back toward the battery - move the meter lead from the starter case to the block, then the cable terminal at the block, then the cable terminal at the battery. Somewhere in there you will find a bad connection or a bad cable.

            Now do the same thing with the positive terminal of the meter on the positive battery terminal and start working back along the wires with the negative meter probe. You will go from the starter stud to the wire terminal to the other end of the wire, the solenoid terminal, the other solenoid terminal and to the battery.

            Somewhere in there you will almost always find a bad cable terminal or just a corroded one that needs cleaning. Bad solenoids are also common and fairly cheap.

            Hope this helps,

            John

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            • #7
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              Re: Mercruiser 4.3L V6 engine WEIRD starting problem (HELP)

              pull all plugs out and then select forward.go to rear of boat and you should be able to turn the engine over fairly freely with the prop.if th engine is struggling to rotate the engine and drive may be out of alignment but as the dealer has already proved they are not reputable and have left what could be a an expensive trouble shooting experience.a have a 1000 cca 120 amp battery for a 5 litre as the boat cannot be towed as in a car as easily.if its very slow in turning the engine over some more investigating on compression,timing and engine alignment to know where to start.the pistons have to suck the fuel in and a slow mturning engine is doing u no favours.

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