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Conference vicki::boats

Title:Powerboats
Notice:Introductions 2 /Classifieds 3 / '97 Ski Season 1267
Moderator:KWLITY::SUTER
Created:Thu May 12 1988
Last Modified:Wed Jun 04 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:1275
Total number of notes:18109

1172.0. "Rough running at high idles in Gear" by NACAD::SWEET () Tue Jun 14 1994 11:00

    I am having a minor problem that maybe someone can suggest a fix for.
    My engine is running rough (seems to be starving for gas) between
    800-1200 rpm. It is a ford 460 with a holley carb (OMC 330HP). It
    runs fine at idle in gear (650RPM). It runs just fine once you bump
    it over about 1200RPM to WOT. I put new plugs, wires, fuel filter,
    cap, rotor, points (set with dwell meter by mechanic) in at the begin
    of the season (I do this every spring). I sprayed some gumout down
    the carb throat and it may of helped some but after a couple of
    more times out the roughness and occasional stall are back.
    
    Trolling season is comming and I need to get this resolved. Any
    suggestions?
    
    Bruce
T.RTitleUserPersonal
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1172.1time to rebuild the carb?SMURF::AMATOJoe AmatoTue Jun 14 1994 12:056
    Bruce
    
    Are you still using the valvtec?  It could be time for a carb rebuild,
    how many hours on the engine?
    
    Joe
1172.2NACAD::SWEETTue Jun 14 1994 13:436
    Yup use the valvtec all the time. I'm hoping the answer is not the
    carb rebuild but it is pointing that way. Engine hours are tough to 
    estimate but figure a min of 800 hrs up to 1100 maybe. The carb was
    rebuilt in the winter of 89/90.
    
    Bruce
1172.3Try points, then expert.SALEM::LAYTONWed Jun 15 1994 09:1515
    I had a car that bogged at about that RPM due to defective points.  The
    car ran OK for a week or so, then started acting up.  Before I went
    ahead and rebuilt the carb, I decided to bring it to my mechanic
    friend; he has a Sun engine analyzer.  He took one look and said
    "Points."  
    
    But more likely yours is a carb problem.  Most carbs have three
    circuits; idle, mid-range, and high speed.  A good carb guy (if you can
    find such a thing) can adjust/repair just the mid-range circuit.
    
    If there's any way to get it on one of those computerized engine
    analyzers (or, more likely, get the analyzer aboard!), you can 
    save yerself a chunk of money and time.
    
    Carl
1172.4not the carbNACAD::SWEETTue Jun 21 1994 15:358
    The saga continues. I pulled off the carb and had it rebuilt.
    The problem pursists. It seems to only miss behave once the engine
    is warm and I run at a fast idle (800-1000rpm) after running up
    at higher revs. It is starting to point back to an electrical problem
    and I guess the coil is the next suspect since it has signs of a
    temperature sensivity. Other suggestions?
    
    Bruce
1172.5brittle wire going to the coil????KAOU93::BROUILLARDCan the fox outrun the rabbitFri Jun 24 1994 16:558
    Make sure to check wiring going to the coil.  I had a ford 351 
    losing power when the motor was warmed up and after spending
    a few $$$ in the shop without any success I took it upon myself
    to find the problem which was the positive cable going to the coil.
    I guess after being exposed to heat and cold it got brittle and crack.
    My 2 cents.
    
    Pascal (ontario)
1172.6Plug or coil wire, insulation breaking downTRIGG::VOGELSteve Vogel - Workgroup/Messaging Sales SpecFri Jun 24 1994 17:117
    I have also seen problems that are only visible at night. IE: the coil
    wire or plug wire(s) that are arcing to the engine block, especially
    when the humidity is high (like around water).  You could clearly see
    the arc after dark but it was unnoticable during the daylight.
    
    /Steve
    
1172.7I think I've got it!4370::SWEETMon Jun 27 1994 11:0616
    I think the problem is solved. After having replaced and tesed most
    every associated with fuel or electric I went back and started
    to recheck and replaced the new components I put in in April.
    Even though the dwell was right and the points were only 3 months
    and less than 100 hours old I found some black/grey singe marks
    on the end and put a new set in. I also put new plugs in again
    (I went back to champion instead of AC) and change the fuel/water
    seperator. The plugs did still look new, the filter was 98% gas
    (very clean compared with usual after a season of use). Things ran
    fine (like it used to but better with a clean carb) so I think it
    was a bad set of points. Haven't got a clue why but the theory
    is somehow they were shorting in that small rpm range at temperature.
    
    Thanks for all the help...
    
    Bruce