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  1. #1

    Default Engine Rebuild-Can't get above 2000 RPM?? Please help!

    So I recently purchased a 1993 Chris Craft Concept 185 with an OMC Cobra 3.0 engine. As it turns out, it had a cracked engine block (that the previous owner "didn't know about") and I ended up rebuilding the engine and replacing the block. I've had it out twice this past week trying to break it in, and I can't get the engine to exceed 2200 RPM, when it's in the water. I noticed it was low on outdrive oil, so I topped it off and ran it on the ears and I was able to get it straight to 4000+. Fluids are good, head was good, pistons and rings are new, harmonic balancer is new, new gaskets, it's been timed, so I can't figure out where the hang up is. I had it to a shop to have it aligned, so I trust that they did it correctly, but I witnessed some of their work and I was extremely shocked and dissatisfied, so I'm not ruling an improper alignment. Any tips would be greatly appreciated. Thanks.

  2. #2
    Join Date
    May 2007
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    Kawarthas
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    3,224

    Default Re: Engine Rebuild-Can't get above 2000 RPM?? Please help!

    start with a compression test. that'll rule out things like valve setting and any sort of ring/piston issue and you can look for water in the cylinders see if the spark plugs show anything weird.

    then triple check timing, then on to the fuel system.

    alignment doesn't have anything to do with low power, nor does drive level. Take 2 pistons out and it'll still rev to 4k in neutral. Power issues only show under load.
    Last edited by hystat; 06-27-2016 at 06:34 AM.
    Factory Manual Best, Seloc 2nd best, Clymer if you're desperate.

  3. #3
    Join Date
    May 2010
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    DC Burbs/Maryland Eastern Shore
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    Default Re: Engine Rebuild-Can't get above 2000 RPM?? Please help!

    Fueling. As in, you aren't getting enough....
    Practicing the ancient art of ren-ching

  4. #4

    Default Re: Engine Rebuild-Can't get above 2000 RPM?? Please help!

    It seems like it's getting plenty of fuel. Once it reaches 2,000 RPM, it reacts as it should. If I keep applying throttle, it bogs the engine and sounds like it's getting more fuel than it can burn and doesn't increase speed, power or RPM.

  5. #5
    Join Date
    May 2010
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    DC Burbs/Maryland Eastern Shore
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    1,107

    Default Re: Engine Rebuild-Can't get above 2000 RPM?? Please help!

    I don't know how you measure fuel flow by ear, but in any case I would suspect the carb before anything else. It starts and runs, idles and accelerates. Then it gets to a certain point and "runs out of gas".
    Practicing the ancient art of ren-ching

  6. #6
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,761

    Default Re: Engine Rebuild-Can't get above 2000 RPM?? Please help!

    does the timing advance as it's supposed to?

  7. #7
    Join Date
    Apr 2016
    Location
    barnegat NJ
    Posts
    2,707

    Default Re: Engine Rebuild-Can't get above 2000 RPM?? Please help!

    Inspect a few plugs that might give a clue, running rich or lean.

  8. #8
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
    Posts
    2,569

    Default Re: Engine Rebuild-Can't get above 2000 RPM?? Please help!

    re:" rebuilding the engine and replacing the block"... and the cam ???? original to your boat or came with new block?
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

  9. #9
    Join Date
    Jun 2009
    Location
    Carbondale, colorado, usa
    Posts
    23

    Default Re: Engine Rebuild-Can't get above 2000 RPM?? Please help!

    I am in the same boat ! I have twin 3.8 liter 4 bbl OMCin a 245 sea ray. Port motor purrs like a kitten at idle, timing advances properly, points were set with a dwell meter,new carb. On the water it runs good up to 2000 rpms and then bogs down and runs like crap. Did you find your problem?

  10. #10
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    9,091

    Default Re: Engine Rebuild-Can't get above 2000 RPM?? Please help!

    Quote Originally Posted by makomark View Post
    does the timing advance as it's supposed to?
    I'll second that question!
    If the ignition system is not delivering the correct progressive and total advance, at the prescribed RPM, the engine will not produce enough power.
    And by the way, I would quit running it until this is sorted out.


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

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

  11. #11

    Default Re: Engine Rebuild-Can't get above 2000 RPM?? Please help!

    I would be willing to bet that If you watch your timing light as you increase the throttle that the spark disappears around the point that it starts to run poorly.

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