Secondaries not opening up 7.4l carburetor - Solved

Discussion in 'Sport Cruisers' started by keysohana, Oct 9, 2019.

  1. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    So I took the Sundancer 330DA on a test run, both motors ran great up to 3000 rpm, except past 3000 rpm, port motor would easily go, up to 4000 rpm, starboard engine would not go past 3000 rpm even at full throttle.
    Also the starboard motor has a few small back fires when she starts cold..not sure if related, but possible.
    Thinking the secondaries are not opening up and it appears they are controlled by a vacuum?
    Does anyone know where to start looking for that or other suggestion?
    Thanks!
     
  2. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Which carburetor do you have?
     
  3. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    Not sure, thinking it is a weber though...
     
  4. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    Note there is a possibility the last mechanic pulled or broke something when doing the manifolds and risers, I found sloppy work after he left including but not limited to 2 spark plug wires not fully inserted onto the plugs, heat exchanger hose not clamped, etc.
    Just not sure where to start looking....
     
  5. Wanderer 290

    Wanderer 290 Member

    105
    Jul 1, 2019
    01 sea ray 290 sundancer
    Twin 5.7 b3’s
    Sounds like the the test run was a failure. Carburetor, timing and or internal issues are present so there are probably better options on the market unless the price is unbelievably great?
     
  6. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    Looks like carb is a weber...I am now leaning towards timing as the issue due to the back fire when started cold...ran great and solid at up to 3000 rpm though, no skips, etc.
    Maybe ignition sensor...
     
  7. Saverio

    Saverio Active Member

    Aug 31, 2010
    Long island new york
    1995 330 DA
    Twin 454 Webber Carbs
    V drives
    Fresh water cooled
    if you check the timing you have to ground one of the wires for the thunderbolt. also double check your firing order. Did you get a survey done when you bought the boat?
     
  8. Voodoochild330

    Voodoochild330 New Member

    13
    Jun 28, 2018
    96 Sundancer 330
    454 V Drive
    Sounds like a carb issue itself. Factory carbs on my 96 330DA were Rochesters. I specifically had them rebuilt (with warranty) and flow tested when I did an overhaul this winter. Oddly enough, port was way too rich even adjusted with the set screws turned all the way in. I warrantied it and now it runs like the day off the show room floor. I did do Electric fuel pump conversions which I recommend and love. Dead cold, I turn ignition switches on, wait 3 seconds (the modules used have 3 second auto-prime) and hold for 2 cycles and it idles flawlessly.
     
  9. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    Thanks, what electric pump conversion did you have done? That sounds like a good idea...
     
  10. Voodoochild330

    Voodoochild330 New Member

    13
    Jun 28, 2018
    96 Sundancer 330
    454 V Drive
    https://www.amazon.com/gp/product/B00029JC62/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

    https://www.amazon.com/gp/product/B00BNZ05JM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

    https://www.amazon.com/gp/product/B00PLKV6C0/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

    https://www.amazon.com/gp/product/B005DSTC6W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

    Snag some block off plates from your local parts store. By-pass your mechanical pumps, turn the pumps down all the way to like 12 PSI and fire up.
     
  11. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    Thanks!
     
  12. ttmott

    ttmott PhD in OCD GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    Careful, not a thing on this list is rated for marine use let alone in a gasoline engine compartment.....
     
  13. Wanderer 290

    Wanderer 290 Member

    105
    Jul 1, 2019
    01 sea ray 290 sundancer
    Twin 5.7 b3’s
    12 psi of fuel pressure is high for a carburetor.
     
    techmitch likes this.
  14. techmitch

    techmitch Well-Known Member GOLD Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    Agree, way too high. Bad advise
     
  15. Saverio

    Saverio Active Member

    Aug 31, 2010
    Long island new york
    1995 330 DA
    Twin 454 Webber Carbs
    V drives
    Fresh water cooled
    my 95 came stock with Weber carbs
    i replaced one with an edelbrock 750
     
  16. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    Thanks!
     
  17. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    Do you like the edelbrock better?
     
  18. keysohana

    keysohana Member

    58
    Sep 12, 2019
    1995 Sundancer 330 DA
    7.4 Carb V drives
    What fuel pump psi do you recommend for a carb 7.4l?
     
  19. hottoddie

    hottoddie Well-Known Member

    Jan 11, 2012
    Boston/Cape Cod
    1986 Sea Ray 390 EC
    Garmin 4212 Chartplotter
    Garmin 24 HD Radar
    Garmin 546s Plotter
    454 Crusaders
    No more than 7 psi. 5-6 is better as 7 psi may overcome the float spring and overfill the carb.
     
  20. Seapig

    Seapig Member

    63
    Dec 25, 2018
    Oakham MA or Winnipesaukee NH
    12 Sundancer 310 w Axius
    Twin 350 Mags w Bravo drives
    Popping back is generally caused by a lean condition. I’d make sure the choke is working right. I’d also make sure the throttle cable is set up correctly. Maybe it’s not stroking fully.

    Mechanical fuel pumps are fine for carburetor engines. If you go electric, use something marine rated and properly wire it off of a relay that’s controlled by an oil pressure switch and cranking by-pass. You don’t ever want a situation where the pump is running continually while the engine is off. If the needle and seat leaked and you left the ignition on by mistake, you’d have gasoline flooding over and laying atop the manifold and possibly fill the crankcase up.

    BOOM !
     

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