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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
    81

    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
    81

    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
    81

    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
    7,885

    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
    842

    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...

  10. #10
    Join Date
    Dec 2014
    Location
    Ontario Canada
    Posts
    81

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

    This is a very handy checklist of possible causes.
    1. Fuel condition. Type and Octane possibly old fuel
    2. Propeller pitch or diameter, damaged blades
    3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
    4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
    5. Marine growth on hull and outdrive
    6. Wrong gear ratio in outdrive
    7. Restricted carburetor air intake (clogged flame arrestor)
    8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
    9. Poor cylinder compression Compression Test
    10. Carburetor defective, or wrong type.
    11. Fuel pump pressure and vacuum
    12. Boat overloaded, improperly loaded, or improperly trimmed.
    13. Engine Overheating
    14. Engine timing and ignition system operation
    15. Remote control cables and linkage for proper travel to open throttle plates fully.

  11. #11
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    11,266

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

    ..........
    Quote Originally Posted by makomark View Post
    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....
    Ditto Mark on that.
    Both engines must see the same progressive advance and a total advance that meet OEM specs.

    You need to find a way to mark off the harmonic balancers, or find a better way to index the flywheels for ignition timing.


    Unfortunately, no one here has been able to find an OEM Chrysler Marine ignition advance curve! Chrysler gives very little information re; this.
    We can find BASE advance all day long... but nothing in the form of a curve graph. Been there/done that many times here!

    Keep in mind that too much may cause the engine to undergo detonation..... and too little will leave power behind!

    Quote Originally Posted by chajohns007 View Post
    I did verify the springs in the advance were there and not rusted, and the advance moved and sprung back.
    There is no real accurate way to tell precisely what the flyweights and return springs are offering (for an advance curve) without the use of a distributor machine.
    See if you can find a shop in your area who owns/operates an old Sun, Allen or King distributor machine.
    They will be able to run each up and look at the curves, and then make adjustments, if need be.
    You should see a rather linear curve, with a 26* TA that comes full-in at around 3,200/3,400 RPM.

    Quote Originally Posted by chajohns007 View Post
    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.
    Yes..... engine rotation is always viewed from the flywheel end.
    CCW = Std LH rotation..... CW = RH Rev Rotation.



    Quote Originally Posted by chajohns007 View Post
    I'm going to swap the carbs between engines.
    That's one beauty of having twins. You can do that as part of your P of E (process of elimination).
    Last edited by RicardoMarine; 10-01-2019 at 09:11 AM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  12. #12
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    11,266

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

    The Chrysler 360 shares a similar bore/stroke and combustion chamber design as with the 5.7L SBC.

    Here are a few examples of a Marine SBC ignition advance curve.

    NOTE: these are not 360 cu in Chrysler Marine curves. use these as a reference only.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

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