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    1986 Mercruiser 470/170hp/3.7L Carb backfire, low vacuum, other weird issues

    Welp all right then looks like she’s going back on the trailer lol. I’ll do a compression test today and post results, yes I have checked ignition timing it’s 4 deg btdc as per the Mercury service bulletin for this engine. Both oil and coolant are clean with no milk although I’m sure it’s about...
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    1986 Mercruiser 470/170hp/3.7L Carb backfire, low vacuum, other weird issues

    Hello everyone I thought I should ask before I asked a mechanic to diagnose for me. I am very acquainted with this engine so any specific or technical answers most likely won’t be lost on me. So I’ve been having carb backfiring/ hesitation under heavy acceleration (no problems slow) only from...
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    1988 Mercruiser 5.7 timing issue.

    It definitely sounds like you are running rich. So if resetting your timing doesn’t fix it you need to look into your air to fuel mixture and determine why it is getting too little air or too much fuel. But I’m confident resetting timing will fix it, if it is wrong.
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    1988 Mercruiser 5.7 timing issue.

    Is it backfiring out of the carberator or exhaust. Since it happens when you try to retard the timing I’m gonna assume it’s exhaust which would mean it’s running rich, try to reset your idle fuel mixture back to factory settings. Setting the engine rpm at such an advanced timing mark is gonna...
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    50 hp high speed misfire

    The little bit of smoke before the sea foam is normal. How long have you ran the engine for after adding the sea foam?
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    50 hp high speed misfire

    Blue/white smoke is normal out of a 2 stroke but if it’s excessive like the entire engine is engulfed in it then no.
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    50 hp high speed misfire

    Blue or white smoke are “uh oh” smoke so hopefully that’s just from the sea foam. Was it happening before you used sea foam?
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    50 hp high speed misfire

    What color is the smoke? (White, Black, Slightly Blueish)
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    50 hp high speed misfire

    I second Nordin on setting the timing after changing trigger.
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    50 hp high speed misfire

    You are correct no distributor on this engine my mistake.
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    Mercruiser 3.0 Trouble Starting

    I am aware of the bulletin. Both the 3.0 and the 3.7 have the rpm range of 650-700 and the timing change from 8 deg btdc to 4 deg btdc as per the bulletin.
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    Mercruiser 3.0 Trouble Starting

    Their ignition systems are nearly identical, points ignition system, single ignition coil, with a distributor that has mechanical advance. They both have a mechanical fuel pump. They also both have 2bbl carbs. The idle speed setting, fuel mixture setting , and idle rpm range are all the same...
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    Mercruiser 3.0 Trouble Starting

    Not really sure what you’re asking but I have an 86 3.7 liter Mercruiser which is basically the same engine just a bigger displacement. And I have done my idle timing before?
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    50 hp high speed misfire

    The distributor I’m referring to is the device that all spark plug wires are attached to, you need to open that up to look at the springs/weights underneath (This is assuming you don’t have an HEI distributor) I would find the factory idle speed and fuel mixture settings for your engine online...
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    Mercruiser 3.0 Trouble Starting

    Okay I have had similar issues and it sounds like your timing/ fuel mixture are off. It sounds like your engine is immediately flooding itself on start up because it isn’t combusting the fuel in the cylinders soon enough. Have you changed fuel/air mixture screw or idle speed screw on carb at...
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    50 hp high speed misfire

    It sounds like your distributor is having mechanical advance or timing problems, if you can open up the distributor and look at the springs underneath the plate that is under the distributor cap. Look for stretched or rusty springs, also clean out gunk inside if you find any. You also need to...
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    1996 Johnson 50. Not starting, backfiring only. Primer issue

    Is it backfiring out of the carberator or the exhaust if it’s out if carb it’s too lean “not enough fuel” if it’s exhaust it’s too rich “too much fuel” either way your combustion is off and if you haven’t messed with idle speed, mixture, or choke setting its most likely a timing issue.
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