mercury 7.5 hp 1971 will not start

G

garcia

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Aug 26, 2011
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Replaced the ignition coils and the plugs and just turns over plenty of spark and every 5 or 6 pulls it back fires what the problem plz help
 
bgc

bgc

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Jul 13, 2011
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Re: mercury 7.5 hp 1971 will not start

Did you switch the spark plug cables?
 
C

Cay

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Re: mercury 7.5 hp 1971 will not start

I tend to agree with bgc. Sounds like a timing issue. The plugs are not firing at the right time. Might the spark plug wires be connected to the wrong coils?
 
G

garcia

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Re: mercury 7.5 hp 1971 will not start

I don't know, it turns over but does not want to crank, just turns over. Its been sitting for years and the other day i had a mechanic work on it. The wires under the stator were ate up and he replaced them and he didn't pay attention to where the wires went on the coil packs, so he tried a couple of ways and couldn't get any spark. I got it home and sprayed some starter fluid in the carb, it stared up, ran good and then i replaced the impeller and put new plugs in it, and now it just turns over.
 
C

Cay

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Re: mercury 7.5 hp 1971 will not start

Starter fuid in the carb is a bad idea in a two cycle engine. It can damage the cylinders. If you must, use gas and oil mixture in a spray bottle.

You need to:
1- Verify that compression is good
2- Confirm that there is spark at the plugs
3- Confirm that fuel mixture is getting to the cylinders.
4- Ensure that timing is correct.

If it 'started up and ran good' after the mechanic, then the wiring is likely in the right place and timing is probably ok. After turning it over a few times, are the plugs wet with fuel?
 
G

garcia

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Re: mercury 7.5 hp 1971 will not start

Ok mix a spray bottle up of mixed gas thanks and no the plugs are not wet with gas and i sprayed it in to the carb and still nothing getting good spark but what now.
 
C

Cay

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Re: mercury 7.5 hp 1971 will not start

Spray a bit of fuel mixture in each cylinder, put plugs back in, and see if it starts and then stalls. If it does, I would then check fuel pump, then carbs.
 
L

Laddies

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Re: mercury 7.5 hp 1971 will not start

The insulator blocks on the points are cracked and shorting to ground giving random spark.
 
G

garcia

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Aug 26, 2011
Messages
6
Re: mercury 7.5 hp 1971 will not start

Well cleaned the carb but before that i put the old spark plugs in and it fired up for about 6 sec and shut of then just turned over and sputters like it wants to crank but dosent after cleaning the carb still nothing but when the fuel goes in and then i drain it out of the fuel line its brown idk what that is help im tired of messing with it thanks
 
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