1978 mercury 800 80hp Wont start/Runs fines when running

sea1tech101

Cadet
Joined
Aug 11, 2010
Messages
17
? Can someone tell me what wrong? Im thinking its a carb problem. accelerator pump if it has one or a float not really sure which it has. And where can I find a good diagram on it.
 

Gomer50

Chief Petty Officer
Joined
Sep 5, 2009
Messages
507
Re: 1978 mercury 800 80hp Wont start/Runs fines when running

A little more information is needed.Wont start/runs fine when running doesnt say much.On mine I need to pump the bulb up tight and advance my small lever on my control box and choke the crap out of it and she will fire up everytime,these motors are cold hearted but once warmed up no problem.If the problem persists when she is warm then this could be a number of things.But if you say she runs fine when running check to see if your choke is working first.Next I would get a squirt bottle and put some pre mix in it and give the carbs a good dose and see if she will fire right up(no starter fluid).Next run some seafoam thru the engine when running to decarb the engine.If your fuel pump is working properly I would then consider cleaning the carbs.Hope this helps.
 

sea1tech101

Cadet
Joined
Aug 11, 2010
Messages
17
Re: 1978 mercury 800 80hp Wont start/Runs fines when running

The motor doesnt start when just regular choked. I have to put some of the pre mix down the carb and then she will crank and run pretty good. And by the way the choke works thats one of the first things I checked.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,086
Re: 1978 mercury 800 80hp Wont start/Runs fines when running

Check the compression. Sometimes if it is low, the motor is hard to start.

Make sure the battery is really cranking her over, and hold the choke button down until she fires.
 
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