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trouble starting 1971 mercury outboard mercury 650

noahsark

New member
have a 1971 mercury ouboard that hasnt been run in bout 4 yrs that i know of. it will turn over but not start it is backfiring also. dont know what to do any suggestions?? i dont know much bout boats this is the first one i have owned. but im really good with engines in general so if anyone can give me some ideas would be real helpful
 
Re: trouble starting 1971 mercury outboard

Motors sitting up for a long time like that don't like it. Fuel turns to gel and rubber dryrots but it is salvagable. You will need to rebuild the carbs and the fuel pump. Replace all the rubber fuel lines. Replace the impeller and change the oil in the lower unit. I highly recommend you get a manual before you start.
 
Re: trouble starting 1971 mercury outboard

I have done the above with a late 70's outboard and it sounds ok out of the water. Time will tell if the engine is fine but ibnfishn's info is spot on.
 
Re: trouble starting 1971 mercury outboard

if it is backfiring , check and make sure the plug wires are on the right plugs.
 
Re: trouble starting 1971 mercury outboard

got engine started after cleaning out both carbs now it runs but cant get the idle right any info? replaced spark plugs and it still has a miss in it. what could be causing that??
 
Re: trouble starting 1971 mercury outboard

any one know where to find a tackometer for 1971 mercury 650 mine plug into the control box but the wires were cut and the end is missing
 
Re: trouble starting 1971 mercury outboard

http://www.maxrules.com/oldmercs/Wiring/1966ona/30.gif Should help with wiring.The harness that plugs into your control is still available.If it's the socket on the control box that's missing,you can always wire it direct.
You can use a modern tach on your motor,set the pole to 6P,hook the brown to one of yellow/red's on the rectifier and not on the brown terminal on the switchbox.
 
Re: trouble starting 1971 mercury outboard

not sure. how do i adjust them??
also i have oil leaking from the center of the prop. whats causing this...
 
Re: trouble starting 1971 mercury outboard

the oil thats leaking from center of prop is black with water mixed in it what could be causing this??
 
Re: trouble starting 1971 mercury outboard

That leak is likely normal on a 2 stroke.------------Not to lose any sleep over that.-----------If you are worried about a leaking lower unit , then have a shop do a simple pressure test.
 
Re: trouble starting 1971 mercury outboard

Agreed, the oil leaking from the hub is just unspent fuel mix. As long as there is just a bit of it there is nothing to worry about.

When you cleaned your carbs, I assume you removed and cleaned the main/idle jets. Did you pay attention to how many turns out you gave each? If you're unsure, start with the idle jets. Turn them in until the are closed, do not overtighten. Then back them out a turn and a half. Now start your motor and listen to the idle. One at a time turn the idle screw in until the engine starts to sputter/miss from running lean. Then back the screw out until the engine sputters/misses from running rich. Note the number of turns it took from missing lean to missing rich. Set the screw at the midpoint between the two. Repeat with the other carbs if any.
 
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