Ford 351 commander distributor and points

whbjr24

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Jun 18, 2011
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5
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.
 

alldodge

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Mar 8, 2009
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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
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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Did you lube the point shoe? Did you file the new points?
 

whbjr24

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Jun 18, 2011
Messages
5
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?

Thanks.
 

Bondo

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Apr 17, 2002
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70,468
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,..??
 
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