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    Mercury 85hp runs fine on Muffs but Boggs down in Sea

    Hi Chris, I have to remove the carb cover to get to the mixture screws as I have the square bowl carburetor. I ended up buying a manual and found the base setting was just 1 turn so I used that when I took the boat out. And she was much better! I started making the adjustments you recommended...
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    Mercury 85hp runs fine on Muffs but Boggs down in Sea

    Chris, I’m taking the boat on the water tomorrow to adjust the carbs. After adjusting the mixture screws do I need to replace the carb cover each time or can I leave the carb throats exposed when trying to accelerate?
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    Mercury 85hp runs fine on Muffs but Boggs down in Sea

    Thanks Chris, Ive never done timing before but youve explained it really well. That being said, and the fact I dont have a timing light, I will try adjusting the mixture screws and hopefully that will do the trick. When I initially got the boat it had a high idle problem which was caused by a...
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    Mercury 85hp runs fine on Muffs but Boggs down in Sea

    Chris, thanks for your comment! It’s interesting that the first thing you mention, or that anyone has mentioned is to adjust the mixture screw. I say that because when I was in the water I took the carb cover off to expose the mixture screws and at the bottom of the casing was a socket from when...
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    Mercury 85hp runs fine on Muffs but Boggs down in Sea

    Hi All! I have a Mercury 85 HP Thunderbolt 1977(I think)serial 7101664 It runs fine on muffs connected to a hose but when I took her out in the sea it starts well but runs rough and will go into gear and can increase speed slightly but once I open her up abit more she bogs down and will stop if...
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    Mercury 850 Outboard super high Idle

    Thanks everyone for all your great ideas! I finally figured out what the problem was and you won’t believe it. I noticed that the carb flaps were not closing totally so I thought maybe something is blocking them open a tiny bit? Well I opened the flaps right up and shone a light in the lower...
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    Mercury 850 Outboard super high Idle

    Wow thats really interesting as my linkage is also against the stop. What Belt are you referring to as being off by one tooth?
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    Mercury 850 Outboard super high Idle

    That sounds logical but whete do I check the linkage? I hope it dosnt involve resetting timing as been watching YouTube vids this morning and that looks way above my pay grade lol
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    Mercury 850 Outboard super high Idle

    Serial is 7101664(Canadian)
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    Mercury 850 Outboard super high Idle

    Sounds like a great trick but I don’t think I can run the outboard whilst doing this as the idle is so super fast and loud. It’s as if the throttle is stuck open but there’s nothing showing this in the cable mechanism.
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    Mercury 850 Outboard super high Idle

    Matt167 I really appreciate your help here. I will check the seals and gaskets but have no idea what you mean with using the propane torch lol
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    Mercury 850 Outboard super high Idle

    Would the vacuum leak cause the high idle or difficulty starting? Any idea where I would look for the leak?
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    Mercury 850 Outboard super high Idle

    Hi Everyone, I have a 1977 Mercury 850 Outboard that was running fine last year and ran fine once this year but the next time I started it, it started with a super high idle. Now it wont start unless I block one of the air intakes and then it will be super high idle again. Any ideas would be...
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