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  1. #1
    Join Date
    Sep 2019
    Location
    SE Michigan
    Posts
    4

    Default Starboard engine surges, powers down and will not pass 2400 rpm.

    Hopefully I can solve this before I go nuts.

    History. Bought the boat, a 1980 from a guy who had it around 10 years and used it little. With unknown history he had reman long locks put in, from 318s to 360s. Per others at the marina the boat was seldom used after that. Transmissions serviced and Holley's on both engines.

    Port engine runs smooth and will idle and rev fine under load. Starboard would at 1500 rpm, but pop out the carb over that, stall and run rough. Would always immediately re start though, but sometimes not run well under load.

    New filters (2nd set) plugs distributor cap rotor wires and took it out no difference. Cleaned bowls and replaced float needles in carbs and it throttled up to a little over 2500) planed and cruised us halfway across erie.

    Then it started acting like someone was moving the throttle up and down between 2500 and 1500 repeatedly. Eventually it would just go from 1500 Rpms to stopped. Immediately would re start and rev up in neutral. Then go into gear and run rough and at least limp at 1500 in gear.

    Pulled into a fuel dock on both engines, starboard rough. Plugs on that engine really black. Cleaned them and adjusted idle screws in a bit for leaner mix. Helped for a while then again no wot and a backfire over 2000 rpm. Re start, rev and slow speed to a marina where she sits now.

    Fuel pump? Or ignition coil. All the symptoms to me say fuel delivery, aside from the black plugs...? I'm stumped.

    Help! Thanks

  2. #2
    Join Date
    Dec 2014
    Location
    Ontario Canada
    Posts
    70

    Default Re: Starboard engine surges, powers down and will not pass 2400 rpm.

    My 318 did that when I had a vacuum leak on the intake manifold. Listen for a hissing sound around the carburetor and make sure all of the plugs are in the intake manifold and the hoses are on the carburetor. If no leak is found have you set the timing? Also check that your spark plug wires are going to the correct cylinders.

  3. #3
    Join Date
    Sep 2019
    Location
    SE Michigan
    Posts
    4

    Default Re: Starboard engine surges, powers down and will not pass 2400 rpm.

    Thanks, I did check the engine with a vacuum gauge. Readings were mostly steady at idle with a little flutter. Checked it against the port engine and the readings and flutter were basically identical so I'm hoping physically no valve/cam issues. As far as timing, I cannot for the life of me see the marks on the flywheel. I did verify the springs in the advance were there and not rusted, and the advance moved and sprung back.

  4. #4
    Join Date
    Dec 2014
    Location
    Ontario Canada
    Posts
    70

    Default Re: Starboard engine surges, powers down and will not pass 2400 rpm.

    What engines are you running? Do you have one standard and one reverse rotation engine, and if so make sure the firing order is correct for each rotation. Black plugs indicate your fuel system is not the issue, unless your choke is stuck closed. Dig into the electrical side.

  5. #5
    Join Date
    Sep 2019
    Location
    SE Michigan
    Posts
    4

    Default Re: Starboard engine surges, powers down and will not pass 2400 rpm.

    Chrysler 360s. Starboard engine accessories run CCW when viewed from the front- which means CW rotation of the flywheel which I take to mean that is my reverse rotation engine. Interesting thought about the choke, maybe it's flapping closed at times...electric chokes on the holleys

  6. #6
    Join Date
    Dec 2014
    Location
    Ontario Canada
    Posts
    70

    Default Re: Starboard engine surges, powers down and will not pass 2400 rpm.

    In my 1972 31' sport sedan with twin 318s and Paragon Vee Drives, the port engine is standard rotation, and the starboard engine is reverse rotation. Another way to
    tell is by looking at the distributors. The reverse rotation engine distributor will have a 3/4" spacer under it like the one in this picture.
    Click image for larger version. 

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  7. #7
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    7,850

    Default Re: Starboard engine surges, powers down and will not pass 2400 rpm.

    may want to make sure the advance mechanism in the distributors are working correctly - the springs are known to rust away and the weights can wear and get bound up, especially if their maintenance has been neglected....very possible given your initial description....

  8. #8
    Join Date
    Nov 2005
    Location
    Chi West, IL, USA
    Posts
    839

    Default Re: Starboard engine surges, powers down and will not pass 2400 rpm.

    Did you swap ignition components (ECU & coil) to the other engine one at a time to see if the condition follows? If you are sure the ignition is fine and distributor advance is working that leaves air/fuel supply. Black plugs indicates a rich mixture. Does the exhaust smell of fuel and turn black when the event occurs? Backfire through an older Holley can damage a power valve.
    A nitrophyl float can become weak as it ages and a brass can develop a leak.

  9. #9
    Join Date
    Sep 2019
    Location
    SE Michigan
    Posts
    4

    Default Re: Starboard engine surges, powers down and will not pass 2400 rpm.

    did swap in a new coil, but not the ignition control box. I pulled all the hard lines and inspected for blockages. New fuel lines and two sets of new filters (in line and water separating). New cap rotor wires and plugs. Tore apart the bowls and cleaned some of the sandy gink from the secondary side passages. New float needles and the vacuum for the secondaries seemed good. My advance springs seemed good and surprisingly not rusty. The advance moved back and forth easily. I did verify the engine is reverse rotation and that the firing order is correct for that.

    Just moved the boat from lake Erie to Huron, the whole way the starboard motor was fine and didn't stall or run rough. Caveat was 2100 rpm was max ever, any throttle over and it would start to falter and the more throttle the quicker it would almost stall until you backed down to 1500 and eased it back to 1800-2000. Seems like starving for fuel, and yet the black plugs....confused.

    I think now that the. Boat is 1/2 hour away rather than 2, I'm going to swap the carbs between engines. Your power valve comment is interesting...

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