merc 45hp bogs down at full throttle

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lbprior1

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Jun 9, 2004
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Greetings, new to boating and already dead in the water! just bought 86 mercury 45hp 4 cyl s/n A948658 running w/ auto blend. Ran great first time out. Took it home replaced some wires that were coroded, cleaned tanks(full of debris and water). Started with great difficulty (lots of cranking) idled rough (coughing) will not come up to speed under load. Suspected debris/water in carbs, removed replaced all seals diaphrams, float valve ... changed bulb, lines and filter. No change runs good at 1/4 throttle, rough at idle (dies easy after a cough) and will not run full throttle and is a bear to start unless warm. Tried to run a 50:1 mix in stead of using auto blend, no different. On top of that my wife is loosing patience with my new project. help!
 
eurolarva

eurolarva

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Joined
Jun 24, 2003
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4,182
Re: merc 45hp bogs down at full throttle

probably gunk in carb that you missed. A tiny spec can mess up your day. Pull carb apart again and soak in fresh gas. Go through each small passage with a thin wire and blow out with compressed air under 30 psi. You might want to consider replacing all the fuel lines and install a glass filter to help prevent the rest of gunk stuck in fuel system
 
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lbprior1

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Jun 9, 2004
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Re: merc 45hp bogs down at full throttle

Thanks eurolarva, I did blow the jets all out when apart and I have rplaced all but the short connecting fuel lines within cowling. I did not use wire though. I noticed there does seem to be a small discharge of fuel coming out of where the linkage between the carbs is (around the post of butterfly), is this a possible air leak? Well I am loath to take the carbs off again but looks like I have no choice. Thanks, I'll let you know what happens.
 
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i610288

Seaman Apprentice
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Sep 24, 2003
Messages
37
Re: merc 45hp bogs down at full throttle

I had the same problems and it was my fuel pump diaphram worn out.You could see little tears in it,and it would make my engine run rich.
 
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lbprior1

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Jun 9, 2004
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Re: merc 45hp bogs down at full throttle

Well, I did as you said and have the same problem. It does idle better but does not come up to full throttle. Can there be and electrical problem?? I am really stumped and all the boat mechanics are two weeks out. Do you have any other ideas?? Thanks, Lee
 
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