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Ford 351 commander distributor and points

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  • Ford 351 commander distributor and points

    My 1987 Ski Supreme began missing ALOT at top end under power. It has the screw type distributor which is apparently Prestolite. I purchased the Sierra 18-5275 tuneup kit. In discussions with a mechanic, he recommended checking the condenser connections as that could lead to the issue. Anyway, the manual has two different point spacing for Prestolite and Mallory distributors. My question is for the same engine, why would the point gap be different between the two distributor caps?
    Reason for question? With the kit installed, it runs worse. really no power. Starts right up, idles ok sorta, but put it in gear and give it gas and it runs terrible - missing.
    And yes I DID make sure that the plug wires are in the exact same position on the new distributor cap. That much I do know.
    According to the manual, Mallory = 0.019 - 0.021 points gap and Prestolite = 0.014 - 0.019. I apparently mistakenly set the gap to 0.020 so tomorrow I'll reset to 0.016 for the Prestolite. Would 0.001 out of tolerance produce this type of result???? Checked spark on one plug and it seemed strong.

    Thanks in advance. New to boats and this old boat while fun has just started this issue.

  • #2
    Not a Ford guy but the dwell angle is more important then the gap. Your dwell as I find it should be between 24-29 degrees
    94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
    95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
    07 SeaDoo GTX
    Raw Water Pump Maintenance
    Merc Adults Only
    G-Dad always said "First Liar doesn't stand a chance"


    • #3
      Did you lube the point shoe? Did you file the new points?
      1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 -

      Past Boats
      1970 Wooster Hellion - Merc 9.8
      2002 SeaRay 190BR - 5.0 - A1G2 - "Cheasheads in Paradise"
      1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

      What’s behind you doesn’t matter.Enzo Ferrari


      • #4
        Ok, so I gapped the points to 0.017. Didn't seem to help. I replaced the wire from the coil to the points as I spotted a small are where the insulation had been shaved down to the wire. Didn't seen to make a difference. After staring at the engine for awhile hoping for divine intervention, I replaced the coil to distributor cap lead. Major difference. So I replaced all the wires since they were the ones in the boat when I bought it from the previous owner. Still misses on the high end but at least it idles now and I can actually moor the boat without the need of an oar! Next is to check the plugs.
        PROBLEM. the manual for a PCM 351 motor does not seem to spec the plug gap.

        Any ideas?



        • #5
          Sign up today
          Still misses on the high end but
          Ayuh,..... That's usually caused by a Lean condition,....

          Have ya checked, 'n changed the fuel filter(s) yet,..??