402 merc power help

jeffmac17

Cadet
Joined
Apr 20, 2011
Messages
13
ok i have a 76 402 merc..starts up fine and will idle fine, pumping lots of water, when i giver some juice on the high idle she wined rite out sounding great, But when i put it into gear and giver some juice she just dont have any power??? thinkig maybe coils?
any help would be great...few things, new spark plugs/fresh 50-1 gas
 

MacDaddy21

Petty Officer 1st Class
Joined
Feb 16, 2011
Messages
280
Re: 402 merc power help

when you say you give some juice on the high idle, do you mean you are lifting the warm up lever, which is the flat lever to the right of the throttle.
 

jeffmac17

Cadet
Joined
Apr 20, 2011
Messages
13
Re: 402 merc power help

yes that is rite, she'll rev rite out...but when you put it into gear it goes but thats it, it will not rev out at all..
 

MacDaddy21

Petty Officer 1st Class
Joined
Feb 16, 2011
Messages
280
Re: 402 merc power help

does it die out when you try to put it into gear? Sorry I havent been able to give you any ideas yet, i'm just trying to get a feel for what you are saying. I have a 79 402 that I have revived so I should be able to help you, I just don't want to give you an answer on too little information. Also, tell me if you have ever rebuilt the carb and the fuel pump, and if you have new fuel lines.
 

jeffmac17

Cadet
Joined
Apr 20, 2011
Messages
13
Re: 402 merc power help

we just got this motor a few months ago..we rebuilt the lower end, new plugs, is about all..she fires up first start idles no prob and like i said when u hit the high idle she will rev rite up sounding good, when u put it in gear you do have to giver some fuel so she will not die, and also when in gear she will not rev up and go like in high idle...
 

MacDaddy21

Petty Officer 1st Class
Joined
Feb 16, 2011
Messages
280
Re: 402 merc power help

okay you need to do a fuel pump rebuild and a carb rebuild. Pull the carb and fuel pump, completely disassemble both. Get a gallon of Chem-Dip or similar carburetor soak. take all the plastic pieces off the carb and fuel pump. take all the hose fittings off your fuel pump. there should be 2 hose fittings that are threaded, and then one screw that is a 7/16" head I think. take those 3 out of the fuel pump, and soak all that along with the carburetor and all its screws and components. Make sure when you remove the idle screw on your carb you count how many turns out it is from a lightly seated position. If your motor is lacking fuel when you put it in gear, you just need to rebuild these 2 components, and also replace the fuel filter that is next to the fuel pump. if you still have the factory one, throw it away. go to academy, and buy the Moeller glass filter. it is very good and worth the 13 dollars. don't use cheap plastic filters as they will get leaks and pinholes and are very cheaply made. Also, when you rebuild your carb, make sure you get a new float, and needle and seat, and ofcourse all the gaskets. the fuel pump rebuild kit comes with the gaskets, the diaphragm, and the check valves. this should fix your problems.
 
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