need help with 1999 25 merc

Joined
Jun 21, 2013
Messages
10
Ok so I bought this motor serial number og990070 and checked the basics compression all was well then I got it home and put it into a drum and cranked it I noticed it wasnt spitting water out so I remove the hose and dig the dirt dobber nest out of it and boom it was fine then I took it out on the lake and got on plane and noticed it was dropping a cyclinder so I took it home and upon further inspection I saw the bottom cyclinder spark plug boot wasnt completely seated again problem solved then I got to wondering what else I could find wrong and needed to be replaced I started with the fuel filter it was indeed almost completely filled with trash so I went on to the carb and removed it and all of its componets when I got the float bowl open the inlet valve was laying in the bowl I think this may have happened when I transported it to the place I was working on it in the back of my truck laying on its side so I break the rest of it down and soak and spray andblow it out when I put it all together on the motor I follow mercs instructions pertaining to the air/fuel setting and for some reason this thing is still running like crap I cant for the life of me figure out why or whats wrong and its smoking pretty good and the plugs are wet and black what gives any help would be greatly appreciated......sorry for the long thread I'm just being as descriptive as I can Thanks!
 

orbanp

Petty Officer 1st Class
Joined
Jun 26, 2011
Messages
324
Re: need help with 1999 25 merc

Welcome to the iBoats forum!

I take you have the service manual for the motor, a pointer to it was some time ago poster here on the forums.
That the engine smokes and the plugs are wet is indicating that the carb is still not working properly.
It could be a worn float valve or some tears in the fuel pump diaphragm.
I would get a carb rebuild kit and would go through the carb again.

Good luck, Peter
 
Joined
Jun 21, 2013
Messages
10
Re: need help with 1999 25 merc

Welcome to the iBoats forum!

I take you have the service manual for the motor, a pointer to it was some time ago poster here on the forums.
That the engine smokes and the plugs are wet is indicating that the carb is still not working properly.
It could be a worn float valve or some tears in the fuel pump diaphragm.
I would get a carb rebuild kit and would go through the carb again.

Good luck, Peter.



Thanks yeah ive got new gaskets and valves and jets on the way I guess I was just expecting after the initial cleaning for it to do a little better than whats its doing, as far as the actual fuel pump part of the carb what would indicate failure on it, because that was the only part I didnt order.
 

carholme

Rear Admiral
Joined
Sep 4, 2010
Messages
4,845
Re: need help with 1999 25 merc

Did you check the float heights when you had the carbs apart?

When it is running like crap, pump the primer bulb and if it improves, you will know that you have a problem in the fuel pump.

Do you have a Merc service manual?

Gerry
 
Joined
Jun 21, 2013
Messages
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Re: need help with 1999 25 merc

Did you check the float heights when you had the carbs apart?

When it is running like crap, pump the primer bulb and if it improves, you will know that you have a problem in the fuel pump.

Do you have a Merc service manual?

Gerry

No I just have bits and pieces of it from what I can find online
 
Joined
Jun 21, 2013
Messages
10
Re: need help with 1999 25 merc

No I just have bits and pieces of it from what I can find online

Also when I was tinkering with it a little while ago I noticed when I abruptly gas on it she bogs down and dies but when I gradually increase rpms it does fine
 
Joined
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Messages
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Re: need help with 1999 25 merc

Also when I was tinkering with it a little while ago I noticed when I abruptly gas on it she bogs down and dies but when I gradually increase rpms it does fine

Oh and no I didnt check float height but if im not mistaken its supposed to be 1 inch from the body to the top of the actual float?
 

carholme

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