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    1984 75hp L4 with unique problem? I'm baffled!

    Well, at least at this writing, replacing the bleed restrictors seems to have solved the problem on my L4. Thanks!
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    1984 75hp L4 with unique problem? I'm baffled!

    BTW: If you would have read any of the earlier posts you would know I tested each plug wire with a 'jump gauge' resulting in a spark that easily jumped 1/2". All of the tests and actions I took were done right and were accurate. Thanks.
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    1984 75hp L4 with unique problem? I'm baffled!

    This post is a FYI to all of you who attempted to help me resolve the issue with my old 75 HP Mercury. I want to say thanks for your time but I had already tried 99% of the suggestions without success. My final guess that the exhaust could be at least partially plugged was wrong as well. I...
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    1984 75hp L4 with unique problem? I'm baffled!

    They all look pretty clean but the plugs are new/low hours. I've not seen any indication of water while cranking the motor with plugs removed.
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    1984 75hp L4 with unique problem? I'm baffled!

    All cylinders seems to be firing. I inspected the plugs when I had them out yesterday. I didn't see any defects. Earlier when I was working on getting the motor running properly, I choked out the carbs with my hand over each. There was plenty of air entering then. Didn't notice any air/fuel...
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    1984 75hp L4 with unique problem? I'm baffled!

    Jimmbo - Just completed another compression test and a spark gap test. I wasn't set up to start and warm up the motor for the compression test so the results are for a cold motor. When I checked compression earlier with a warm motor, there was 145 psi on all cylinders. The cold results were...
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    1984 75hp L4 with unique problem? I'm baffled!

    Thanks Fazbullet. Dirt dobbers had entered my mind as a possibility. Removing the gear case to get a look up the exhaust is next on my list...after all other possibilities have been looked into. Thanks again!
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    1984 75hp L4 with unique problem? I'm baffled!

    Spark will jump a 3/8"+ gap. I will check spark gap again at the time I'm doing another compression test and post the results. May be able to get it done today...if I get the time.
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    1984 75hp L4 with unique problem? I'm baffled!

    Timing light says all are firing.
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    1984 75hp L4 with unique problem? I'm baffled!

    Jimmbo - I sprayed premix into the carbs at an idle when I was trying to decide if the idle needed to be richened up. At 1 1/2 turns, the motor liked the extra fuel. I'm at 2 1/4 and a shot of premix will load it up so I stayed at 2 1/4. I set the floats to spec when I had the carbs apart. I'll...
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    1984 75hp L4 with unique problem? I'm baffled!

    Nothing different about any of the plugs. They all looked the same. I replaced them but probably didn't need to. Dropping the gearcase to have a look was my next step unless I got some info that sent me in another direction.
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    1984 75hp L4 with unique problem? I'm baffled!

    Chris 1956 - New plugs. The old plugs all looked the same; none stood out as different. The motor came off of an 18' fiberglass bass boat MFG unknown. I put it on my 18' Landau pontoon boat. The prop is a 13 1/4 x 19. If the thing would start and run when the lower unit is submerged, it would be...
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    1984 75hp L4 with unique problem? I'm baffled!

    MORE DETAILED INFO: All input is valued and appreciated. Let me tell you in greater detail what I've done to this motor before I discovered the current issue: I either ohmed or checked direct voltage on the coils, trigger, stator and switchbox. Replaced one coil and the switchbox. Checked the...
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    1984 75hp L4 with unique problem? I'm baffled!

    Thanks. I'm aware of the risks.
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    1984 75hp L4 with unique problem? I'm baffled!

    Jimmbo - Certainly wasn't trying to chase off racerone. Was simply letting him know I had already tried/checked his suggestions. I have eliminated all of typical, normal issues leaving me baffled. I thoroughly cleaned the carbs. If you're suggesting a carb may be plugged only allowing 2...
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    1984 75hp L4 with unique problem? I'm baffled!

    racerone - I appreciate your attempt to school me on motor basics but...Timing light shows the motor IS running on all 4 cylinders. Spark will jump 3/8"+ on each plug lead. Simple 2 stroke carbs cleaned and working. 145 PSI compression on each cylinder. Less than 10% leak down on each cylinder...
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    1984 75hp L4 with unique problem? I'm baffled!

    Chris1956 - I appreciate the reply. I have already covered your suggestion. Link and synch are good. I started with the idle jets at 1 1/2 and they are now at 2 1/4 in order to get it idling good. The problem seems to be something else. Thanks!
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    1984 75hp L4 with unique problem? I'm baffled!

    I acquired this old motor without knowing its history but it had excellent compression and passed the leak down test with flying colors. I have jumped through all (and I mean ALL) of the hoops and troubleshooting on this old outboard and have it running fine while hooked up to water using...
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