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  1. #1
    Join Date
    Aug 2019
    Location
    Lorain, Ohio
    Posts
    35

    Post Need help on AQ225D Distributor OR fuel issue

    Hi guys, just bought a new to me 1984 Sportcraft 250 Hardtop with a 305 in it attached to a 280-PT Duoprop. 800hrs on the engine/outdrive, and decent maintenance on it thus far. I know the boat has good compression and is a great runner, as I used the boat many times this season with my buddy and just finally got around to buying it from him.

    I apologize for the lengthy info, I just like to be as thorough as possible when describing problems, and thank you very much for anyone able to help shed some light on these questions I have.

    At the beginning of the season, the boat was running a little rough here and there, so we changed the hei distributor because the old one was whooped/had broken advance springs and signs of potential humidity intrusion/et cetera. Then, about a month ago we kept getting stranded randomly as the engine would randomly cut out Sometimes under way, sometimes during idle, and sometimes wouldn't crank back up with no rhyme or reason to any of it. We assumed fuel because, after all, the entire ignition was brand new along with fresh 8mo old high end wires and plugs.

    So, a local marina buddy rebuilt the quadrajet 4bbl carb for me, and overall the boat ran great after all that to 4400rpm at wot like usual and we assumed the problem must've been the carb. But, then it started doing it again only two trips later. So, we hunted and hunted and narrowed down the problem to no spark; the module in the distributor was bad at only a month old (US made Marine flamethrower) as they used a gnats ass amount of heat sync paste and barely any of the modules underside was covered. So we realized it got heat stroke and was crapping out.

    So, we replaced the module with a GM module we had from one of our other distributors, and the boat decided to run great again in the slip, but we had already bought a new Carter marine fuel pump in anticipation of it being a fuel issue so we put it in too before going out on a test run. Well, she started up, idled, and revved amazing in the slip after the fuel pump swap too, so we then double checked timing as precaution and timing was good so we planned out a test run. But, when getting out of Lorain Harbor (Lake Erie/Ohio) and on to planing, we're only getting 2500-2800rpms underway at around 1/2throttle or so, and only gain to 3000rpms or so past 1/2 way all the way up to wot.. So, in short, top end is all of a sudden not there since changing the fuel pump and putting in the new module. So, obviously it leads me to either the module not keeping up (I don't know if that is even possible because I'm not ENTIRELY sure exactly how the module operates in depth) or the fuel pump somehow.

    Which leads me to my questions: I noticed that there was no spacer inbetween the fuel pump and block when installed by my buddy, and the old pump didn't have a spacer there either (at least I don't think I seen one on it, but I can't be 100% sure). But, the new fuel pump is slightly different in shape/depth and it came with two thin gaskets in the box, which leads me to wonder if there's supposed to be a spacer inbetween them on this AQ225D (305 GM engine), as I know other engines have a spacer inbetween the pump and block often. It idles great, revs up high heat great while in neutral, but doesn't get past around 2800-3000rpm under load. Would absence of a spacer cause that kind of potential behavior IF that'd be the culprit (ie- does it change pressure or volume in its absence)? Or, is it something to do with the GM module we swapped into the flamethrower distributor not being able to keep up with the advance of the distributor? I'm just kinda at a loss here and have no idea what to target.

    Ran great with the new distributor until the module in it crapped out. Then swapped in a module from another distributor and changed out the fuel pump and now no top end rpms when under load.

    Thanks for reading my essay, and any insight will surely be appreciated because my Seloc manual has nothing regarding these answers in it.

  2. #2
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    11,131

    Default Re: Need help on AQ225D Distributor OR fuel issue

    .............
    Quote Originally Posted by Walleye4Days View Post
    Hi guys, just bought a new to me 1984 Sportcraft 250 Hardtop with a 305 in it attached to a 280-PT Duoprop. 800hrs on the engine/outdrive, and decent maintenance on it thus far. I know the boat has good compression and is a great runner, as I used the boat many times this season with my buddy and just finally got around to buying it from him.

    I apologize for the lengthy info, I just like to be as thorough as possible when describing problems, and thank you very much for anyone able to help shed some light on these questions I have.

    At the beginning of the season, the boat was running a little rough here and there, so we changed the hei distributor because the old one was whooped/had broken advance springs and signs of potential humidity intrusion/et cetera. Then, about a month ago we kept getting stranded randomly as the engine would randomly cut out Sometimes under way, sometimes during idle, and sometimes wouldn't crank back up with no rhyme or reason to any of it. We assumed fuel because, after all, the entire ignition was brand new along with fresh 8mo old high end wires and plugs.

    So, a local marina buddy rebuilt the quadrajet 4bbl carb for me, and overall the boat ran great after all that to 4400rpm at wot like usual and we assumed the problem must've been the carb. But, then it started doing it again only two trips later. So, we hunted and hunted and narrowed down the problem to no spark; the module in the distributor was bad at only a month old (US made Marine flamethrower) as they used a gnats ass amount of heat sync paste and barely any of the modules underside was covered. So we realized it got heat stroke and was crapping out.

    So, we replaced the module with a GM module we had from one of our other distributors, and the boat decided to run great again in the slip, but we had already bought a new Carter marine fuel pump in anticipation of it being a fuel issue so we put it in too before going out on a test run. Well, she started up, idled, and revved amazing in the slip after the fuel pump swap too, so we then double checked timing as precaution and timing was good so we planned out a test run. But, when getting out of Lorain Harbor (Lake Erie/Ohio) and on to planing, we're only getting 2500-2800rpms underway at around 1/2throttle or so, and only gain to 3000rpms or so past 1/2 way all the way up to wot.. So, in short, top end is all of a sudden not there since changing the fuel pump and putting in the new module. So, obviously it leads me to either the module not keeping up (I don't know if that is even possible because I'm not ENTIRELY sure exactly how the module operates in depth) or the fuel pump somehow.
    It is critically important that the ignition system deliver the correct Progressive and Total advance at the prescribed RPM.
    See your OEM service or work shop manual for these specs and ignition advance curve!
    ** When say ignition module, are you talking about an EST ignition system, or are you talking about a pick up sensor in a mechanically advancing system?

    Which leads me to my questions: I noticed that there was no spacer inbetween the fuel pump and block when installed by my buddy, and the old pump didn't have a spacer there either (at least I don't think I seen one on it, but I can't be 100% sure).
    I have never seen any type of spacer used between the mechanical fuel pump and the cylinder block.
    There will be an adapter plate.... but no spacer to my knowledge!


    But, the new fuel pump is slightly different in shape/depth and it came with two thin gaskets in the box,
    Yes, one gasket for behind the plate, and one gasket for between the pump and plate.

    which leads me to wonder if there's supposed to be a spacer inbetween them on this AQ225D (305 GM engine), as I know other engines have a spacer inbetween the pump and block often.
    I would like to see this spacer!

    It idles great, revs up high heat great while in neutral, but doesn't get past around 2800-3000rpm under load.
    Testing RPM while in neutral is rather fruitless.

    Would absence of a spacer cause that kind of potential behavior IF that'd be the culprit (ie- does it change pressure or volume in its absence)?
    The mechanical fuel pump's actuator arm is driven by a push rod that rides on a cam lobe.
    The arm must extend into the cavity and correctly contact the push rod.
    A spacer of sorts would limit the pump's ability, and may also cause slack between the arm and push rod.


    Or, is it something to do with the GM module we swapped into the flamethrower distributor not being able to keep up with the advance of the distributor? I'm just kinda at a loss here and have no idea what to target.
    See ** above

    Ran great with the new distributor until the module in it crapped out. Then swapped in a module from another distributor and changed out the fuel pump and now no top end rpms when under load.

    Thanks for reading my essay, and any insight will surely be appreciated because my Seloc manual has nothing regarding these answers in it.
    Toss that Seloc manual into the recycle bin, and get yourself an OEM service or work shop manual.
    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.

  3. #3
    Join Date
    Aug 2019
    Location
    Lorain, Ohio
    Posts
    35

    Default Re: Need help on AQ225D Distributor OR fuel issue

    The ignition type I'm talking about is with a pickup and mechanical advance (hei system with internal coil).

    The spacer I was referring to was the adapter plate. I didn't know it was called an adapter plate, so I just called it a spacer. (Thanks for the correction)

    If I didn't have that adapter plate between the block and pump, I would have much more noticeable problems than just reduced top end right?

    The timing on the engine is at 8*BTDC and only 24* mechanical advance on the distributor, and both seem to be operating correctly with the timing light (30* at 3500rpm). Just under load I'm not getting it to cooperate.
    1984 Sportcraft 250 Fisherman Hardtop
    AQ225D 305 with an 280-PT Duoprop

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