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Boat wont start when hot

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  • Boat wont start when hot

    87 omc 5.7 with cobra. first time i started boat since i last winterized it last September and boat fired right up. after idling for 30 minutes no driving i restarted boat to see how it went on a warm start. engine turned but wouldn't actually fire. tried multiple times with atleast up to 15 to 20 minutes after it was last run and still couldnt get it to fire. moving throttle seemed to still pump gas into carb. last season carb was rebuilt and new spark plug wires and a new fuel pump were installed. belts turning when it wouldnt start and everything seemed to sound good. battery charged i had more than one aswell. during initial running oil pressure engine temp gauges were all in good levels and working. any ideas on why it wouldnt crank hot?

  • #2
    If its not fuel then it has to be spark. Could be as things heat up the spark gets weak and is not enough to fire. Start with the basics and see if you have power at the coil when cranking.

    Do check to see if the carb is flooding, and have you tried opening the throttle a little while cranking?

    94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
    95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
    07 Seadoo GTX
    Merc Adults Only VP Adults Only
    G-Dad always said "First Liar doesn't stand a chance"

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    • #3
      Not sure of your setup but I had trouble hot cranking after my Holley carb was rebuilt. It has electric choke and I had adjusted it the wrong direction by one click. Corrected the adjustment and now it cranks great hot or cold.
      Sparky
      1995 Four Winns Horizon 190
      5.0 HO
      SX Drive

      http://community.webshots.com/user/sparkinatorST

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      • #4
        Originally posted by Sparkinator View Post
        Not sure of your setup but I had trouble hot cranking after my Holley carb was rebuilt. It has electric choke and I had adjusted it the wrong direction by one click. Corrected the adjustment and now it cranks great hot or cold.
        boat ran fine for multiple months at end of season after the carb rebuild its just now that it doesnt start when hot after reopening the boat the other day

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        • #5
          Originally posted by AllDodge View Post
          If its not fuel then it has to be spark. Could be as things heat up the spark gets weak and is not enough to fire. Start with the basics and see if you have power at the coil when cranking.

          Do check to see if the carb is flooding, and have you tried opening the throttle a little while cranking?
          i was leaning towards spark. im going to replace the coil because its old anyways. i dont believe its fuel as it seemed to run perfect until i shut it down and it also seems to still be getting plenty of gas when i move the throttle. i also tried starting the boat with wot throttle and pumping it and starting in half throttle aswell. couldnt get it to even cough, it might be rich but seems like i shouldve been able to start it still with extra throttle. i was looking down carb throat when it wouldnt start and was seeing any leaking of gas or anything. after new coil ill have to test around. how much volts should i have at coil when cranking and is theyre anything else i should test for?

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          • #6
            You should have 12V or more running or while cranking
            94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
            95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
            07 Seadoo GTX
            Merc Adults Only VP Adults Only
            G-Dad always said "First Liar doesn't stand a chance"

            Comment


            • #7
              Originally posted by AllDodge View Post
              You should have 12V or more running or while cranking
              spark plugs looks like a way less extreme of the photo shown below. maybe that could be part of the issue. either way why would my plugs be burning like this?
              Attached Files

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              • #8
                Can be from to much fuel aditives (seafoam, and others), but in most cases its from leaking valve seals

                Was the correct plug used?
                94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
                95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
                07 Seadoo GTX
                Merc Adults Only VP Adults Only
                G-Dad always said "First Liar doesn't stand a chance"

                Comment


                • #9
                  only used seafoam at end of last season. does seem like theres oil around the base of plugs and yes i used mr34t

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                  • #10
                    Before you go changing the coil (which by the way hardly ever fails) check for spark and if it is weak....your '87 OMC most likely still has a points distributor. these need regular maintenance...check the points for burning, arcing and proper adjustment and the dist cap for corroded terminals. You probably have something like this Prestolite unless someone changed it for an electronic distributor....if you have an electronic...might need to change the module...or at least test it if you have the specs on it....
                    I have changed the points and condenser approx. every 4-5 seasons, or if it starts running rough, then right away. Cap & rotor....usually every other season.....
                    1988 Four Winns 200 Horizon
                    4.3 OMC Cobra

                    98 Jeep Grand Cherokee 4.0 Selectrac
                    07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

                    "While air doesn't freeze....rust never sleeps"

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                    • #11
                      Originally posted by Lou C View Post
                      Before you go changing the coil (which by the way hardly ever fails) check for spark and if it is weak....your '87 OMC most likely still has a points distributor. these need regular maintenance...check the points for burning, arcing and proper adjustment and the dist cap for corroded terminals. You probably have something like this Prestolite unless someone changed it for an electronic distributor....if you have an electronic...might need to change the module...or at least test it if you have the specs on it....
                      I have changed the points and condenser approx. every 4-5 seasons, or if it starts running rough, then right away. Cap & rotor....usually every other season.....
                      distributor isnt corroding replaced last year and yes i believe its a mallory electronic setup actually. idk the specifications. the only numbers i can find on it are 339f on the outside of distributor and then a sticker with the numbers 7145 on it on the dist cap. whats the best way to check for weak spark?
                      Last edited by Buddersnaps; August 14th, 2019, 07:05 PM.

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                      • #12
                        Originally posted by Lou C View Post
                        Before you go changing the coil (which by the way hardly ever fails) check for spark and if it is weak....your '87 OMC most likely still has a points distributor. these need regular maintenance...check the points for burning, arcing and proper adjustment and the dist cap for corroded terminals. You probably have something like this Prestolite unless someone changed it for an electronic distributor....if you have an electronic...might need to change the module...or at least test it if you have the specs on it....
                        I have changed the points and condenser approx. every 4-5 seasons, or if it starts running rough, then right away. Cap & rotor....usually every other season.....
                        also while cleaning all connections around the coil and distributor i found a connection coming out of the distributor connected to 3 wires. a green went to the negative on the coil. a red went to what looked like a resistor and out the other end to the positive side of the coil. then there was a brown wire connected to nothing? could that be anything?

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                        • #13
                          Classic symptoms of the ignition condenser on the way out.
                          ....

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                          • #14
                            Originally posted by dingbat View Post
                            Classic symptoms of the ignition condenser on the way out.
                            do i have that with my electronic ignition. i dont know anything about condensers sorry. if so how do i go about testing the condenser?

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                            • #15
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                              Originally posted by Buddersnaps View Post

                              do i have that with my electronic ignition.
                              In that case, it's the HEI Ignition module going out.

                              Heat related failures are the by-product of thermal expansion in a electrical component.

                              Capacitors are notorious for their intermittent, "now they work, now they don't", heat related failures.
                              ....

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