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Acceleration problem

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  • Acceleration problem

    This being my second mech post today some may wonder if I can be helped :-) But here goes with my larger issue. PCM 302 raw water cooled probably mid 70s engine. Starts, idles, and runs fine up to about half throttle (2000rpm I am guessing) Push throttle from there to WOT and I get no addition rpms or speed. This happened the last two times out. Had to bring her home slow. Prior to that she ran normal. First effort to get at problem was a carb kit and complete disassembly, cleaning and replacement of all gaskets in Holley 450 from National carb. Carb is only a year old but I was afraid I had contaminated it with bad fuel. Put carb back on and the second trip out was the same. Fine until half throttle nothing after that. Does not stumble. Just does not respond. Verified secondaries opening but too dark to tell if getting fuel. Anyway moved on to suspect ignition. Installed new points and set timing. Test run in backyard is fine but have to go to ramp and test drive to make sure. However I am doubtful this solved the problem. Oh I also have checked the fuel pump and it seems to be functioning properly.

    So while folks give this some thought I would add that about the time I noticed this bad behavior two rides ago I also noticed that my tach had taken a dump. Any chance this is a clue to the problem. Could a dead tach somehow impact the ignition system such to cause the kind of behavior I am seeing? Thanks...

  • #2
    Before I did anything would verify ample fuel is getting to the back barrels by looking straight down the secondaries when you are running her. Sounds like this occurred without any other changes to the boat.
    C Rhodes
    26' Mackinaw - 1990
    351 Indmar (1990-2006: Great Engine)
    351 PCM (2006 - Current)
    Southport, NC

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    • #3
      Right on Cecil! This sounds like a fuel delivery issue Daddio! (Appropriate vernacular for the 1970's engine, LOL!)

      A restriction is somewhere between the carb and the fuel tank(s). Could be fuel pump, fuel filter, fuel lines, check valves, etc. Do you have a helper where you could hook up a five-gallon fuel can and run it off that in the water? That could serve to narrow down where in the fuel stream the issue is.

      1987 26' Hardtop
      1996 20' Walkaround Cuddy

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      • #4
        Interestingly I do have one of those cheap see thru small filters plumbed in just before the fuel pump. I like being able to quick view fuel condition as well as get a little extra filtering just in case. While running at half throttle with a helper driving I pinched the fuel line shut until that little filter was about empty then opened the line quickly and fuel poured into that filter as fast as expected. I was thinking that this verified fuel pump health and good flow through the system. However plumbing in and testing with a separate can of fresh fuel is a good idea as well. If same result I guess the solution lies elsewhere other than the tank and main filter. Thanks folks. I will try the fresh can of fuel next outting. Also I am doing a few things to the ignition system as well. New points and rotor, check timing etc. I did notice in the distributor that the advance plates are pretty rusty. Wonder if I am not getting sufficient advance...

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        • #5
          I had the same problem last year. It was ignition and timing.It would run fine with just me, also would run fine on the hose. Any kind of load and 2000-2500 rpms was the max I could get it too. PCM 351.

          If all fuel related stuff checks out.....that would be where I would look next.

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          • #6
            Sorry for slow response. Had to take some time off of shamrock work. Anyway I was checking timing the other day. Set at 10btdc and she starts and idles fine on the hose but bump up to 2k rpm and I only get total 16-18 degrees advance. This seems low. Should be closer to 30ish eh? But my knowledge of distributors is pretty thin... How do I check to make sure the distributor is advancing? And if not how to fix? New distributor? also my distributor has a vacuum fitting but no vacuum line. I am wondering if in her long unknown past if some fitted it with an auto distributor... Thanks...

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            • #7
              The vacuum diaphragm is a dead give away. Yes it's an automotive. No advance happening. I went to:
              https://skipwhiteperformance.com/cat...0-k-kit_95141/
              Atlantic City, NJ
              1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

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              • #8
                Thanks for the distributor recommendation. But before I go that route let me provide some additional info. Until recently the boat has run great with the auto distributor . And interestingly enough it has never had a hose run to the vacuum advance. I just assumed it was plugged off somewhere and only using mechanical advance. On the other hand though I checked the timing last week and it was set for 10 degrees at idle which seemed fine but when I increased throttle up just over 2k rpm total advance was only about 16-18 degrees. Clearly not enough. I am thinking now that I need to take a closer look at current distributor to make sure springs are in place and that weights are actually functioning. I am thinking 2300 rpm advance should be well into mid 20s degree range. I would welcome any other thoughts as I find time to do more research on the engine.

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                • #9
                  Ship FYI that distributor you linked above is not a marine unit either- it has a vacuum canister as well but more importantly it has a gear for a roller cam. If the OP does not have a roller cam in his engine they will not play well together. It says not for industrial engines as well, the marine part of Ford was under the Industrial division.
                  To daddio that distributor you have now is not ignition protected it could ignite any gas fumes. Not good.

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                  • #10
                    Gary, I didn't catch that. I bought mine a couple years ago and when I looked it up, the one I posted looked like mine. I called them to verify what I needed back then. I don't have the paperwork for it anymore or I would have posted the model numbers. I am sure what they shipped was marine. Everything was sealed and gasketed.
                    Last edited by Ship; 09-18-2021, 10:38 AM.
                    Atlantic City, NJ
                    1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

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                    • #11
                      Thanks guys... I did realize the linked one was not a marine type. My plan is to determine that distributor and lack of advance is the acceleration problem and then order something. I also realize my current distributor is not spark protected which I suppose I should correct regardless of that solving the acceleration problem or not. Assuming I do have to eventually replace my distributor can anyone shoot me a link of one that will work in marine environment for my 302? Thanks. Rick

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                      • #12
                        Skip white DID have marine components. I just posted the wrong stuff.
                        Atlantic City, NJ
                        1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

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                        • #13
                          I use Skip White distributors with no problem.
                          1988 26' cuddy
                          1975 20' open
                          16' Sandpiper
                          14' Certified Fiberglass

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                          • #14
                            On Jerry's recommendation I've got a Skip White in my RW 302 also with no issue. She'll run right up for me with no vacuum line hooked up.
                            Chip
                            Camden, Delaware

                            1989 Shamrock 20 Cuddy Cabin (Rock Bottom)
                            PCM 302, RWC

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                            • #15
                              Before jumping too hard on the distributor/timing, verify the secondaries are getting plenty of fuel as previously discussed. (Could be a stuck back barrel float.) I'm a firm believer in making only one change at a time so as to not confuse the troubleshooting process. Rule one thing out then move on to the other. After all it was working correctly with the current distributor and the problem surfaced without a change being induced. My 2 cents worth.
                              C Rhodes
                              26' Mackinaw - 1990
                              351 Indmar (1990-2006: Great Engine)
                              351 PCM (2006 - Current)
                              Southport, NC

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