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  1. #1

    Default '88 Pleasurecraft 302 shuts down after 20-30 mins

    I'm hoping someone can assist as we're out of ideas.

    The engine starts right up and runs beautifully for about 20-30 minutes, then a quick sputter and shuts down. At that point, it won't restart until it cools completely. This can be replicated both under load and on the mooring/dock.

    When it's in it's "dead zone," the carb is getting fuel, but the spark is very weak.

    We've gone over everything we can think of, reviewed manuals, consulted mechanics, etc and everyone is flummoxed.

    I believe we've narrowed the issue to electrical. According to manuals and the Mallory ignition troubleshooting guides, I should be getting +/- 6v into the coil and out of the ballast. Both before and after the shutdown, we're reading +/- 12v. So it seems like the ignition system is overheating.

    We've replaced the coil and ballast, no change. Tested the ignition module in the distributor (Mallory 609), found it bad and replaced it, no change. Cleaned up and re-tightened every ground we could find, no change.

    Any thoughts or suggestions on where to go next would be greatly appreciated. Thx

  2. #2
    Join Date
    Sep 2008
    Location
    Maryland - USA
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    Default Re: '88 Pleasurecraft 302 shuts down after 20-30 mins

    It should NOT be +/- 6VDC into the coil....more like +9VDC when its running.....

    If its reading +12VDC into the coil when its running, then there's no current running thru the primary which will give you a weak (or no) spark.

    I'd be inclined to check the ground wires (not just the connectors on the ends....20 years can enable a lot of corrosion to occur....

  3. #3

    Default Re: '88 Pleasurecraft 302 shuts down after 20-30 mins

    Thanks...I'll check them out.

  4. #4
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    Sep 2008
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    Default Re: '88 Pleasurecraft 302 shuts down after 20-30 mins

    if the ground wires are serviceable, you want to inspect/clean the main wiring harness connector.

    Also, I'd suspect a bad connection somewhere and an IR thermometer can be a great asset looking for those....and much quicker than running your fingers along a wiring harness...

  5. #5

    Default Re: '88 Pleasurecraft 302 shuts down after 20-30 mins

    Thanks Makomark...I did as suggested. Also was able to locate an old wiring diagram. It looked like the wiring between the distributor, ignition and coil was screwy. Did a little re-wiring. Now getting +/-10v on positive side of coil and +/-9v on neg. Still have to check voltage at ballast. So moving in the right direction I think.

  6. #6
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    Sep 2008
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    Default Re: '88 Pleasurecraft 302 shuts down after 20-30 mins

    It can't be +/- if you are using a meter - do you mean "approximately" or "about" when you use " +/-"?

    where the measurements posted in Post #5 taken running? if so, did you run it long enough to get past the 30 minute point?

  7. #7

    Default Re: '88 Pleasurecraft 302 shuts down after 20-30 mins

    I apologize...yes the +/- is intended to mean approximately. The meter readings bounce a bit from 9.7 to 10.2 or 10.3 and a bit less than 8 to a shade over 9.

    The readings were taken while running, but not up to the usual failure point. Will be doing that this afternoon.

    Thx...

  8. #8
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    Default Re: '88 Pleasurecraft 302 shuts down after 20-30 mins

    good luck!!

  9. #9

    Default Re: '88 Pleasurecraft 302 shuts down after 20-30 mins

    Sunday afternoon, it seemed like we had it under control. The motor stayed running for almost an hour and we were able to bay test thru a range of RPMs from idle speed up thru 3500-4000. On return to the channel (and dropping the RPMs), the motor stalled, but it started right back up. Voltages stayed in the previously reported range - 10 or so on the positive terminal and 8.5 - 9 on the negative. Alternator is putting out a consistent 13.5 - 14.5v. Any further thoughts on what to check?

    Thx!

  10. #10
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    Sep 2008
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    Default Re: '88 Pleasurecraft 302 shuts down after 20-30 mins

    did you have the meter hooked up when it quit? If so, what readings were obtained? sometimes, a test light is a better tool to use when looking for intermittents….

    The only other thing that comes to mind is the wiggle test....start at the coil/distributor end and being careful with the engine running, wiggle each connector/harness connection and wire up thru the main connector up to the key switch....you'll know immediately when you bump the bad joint...

  11. #11

    Default Re: '88 Pleasurecraft 302 shuts down after 20-30 mins

    Did you ever determine the root cause? I am having similar issues with my 81 Mastercraft S&S. Runs great for first 20-30 mins, then bogs terribly and no power. Strange thing I noticed last time out was when I was nursing it back to the dock the engine increased RPM's & power when the Bilge Blower was on. Turned off the Bilge Blower and it lost RPM and slowed again. I originally thought the issue was with the carb, but rebuilt carb and issue remained. Now looks to be electrical related. Any suggestions?

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