Mercury 25 hp Bogging from idle

[neue0014]

Hi Everyone,

I am the new owner of a 2003 mercury 25 (2-stroke) ELH. I replaced the water pump, cleaned the fuel filter and put in new gas and spark plugs and compression checks 100+ on both. I can run it across the lake when first out great, no issues. Out of no where it will drop RPM and bog down to idle (dying if i do not turn back the throttle, fuel bulb is still hard). I have tried adjusting the air/fuel screw? How far can i turn it in, or out? Any ideas of why it all of the sudden it wont gain rpm's and bog's? Also, if i turn it off and let it sit for a minute, I start it back up and it will run great for about 30 seconds until it begins bogging again. Thanks.

 

[Dave1027]

Re: Mercury 25 hp Bogging from idle

The air fuel screw (idle mixture) has nothing to do with your problem which could be either losing spark in a cylinder or a restriction in the main fuel circuit of a carb. Probably the latter.

 

[windy5849]

Re: Mercury 25 hp Bogging from idle

Have you checked the gas tank vent to make sure it is open or that the vent is not clogged? Simple,but worth a try.

 

[neue0014]

Re: Mercury 25 hp Bogging from idle

Dave: I have only one carb, and i will check the main jet and carb bowl this evening for anything that could obstuct the passage. Any way of testing the spark theory. It does make sense and when running sounds like it is bogging trying to make power. How would i go about testing this and what would i need to replace to make sure this is not a symptom. Both plugs were burnt cocca brown like they were both firing? Thanks

Windy: I did check the vent and it was open , Thanks


Thanks for the quick responses. This place rocks

 

[Dave1027]

Re: Mercury 25 hp Bogging from idle

I would chase down the fuel angle first (main circuit intermittent). Going by your description it makes more sense. Think about it. The idle circuit is working fine. That's why when you reduce throttle things come back to normal. I think you have eliminated a fuel pump issue because you did check the bulb while running indicating you probably tried squeezing it.

 

[neue0014]

Re: Mercury 25 hp Bogging from idle

Cleaned and rebuilt the carb over the last two nights. Looking to run her tonight or tomorrow out on the lake to find out if the problem is fixed. I cannot do it at home as the motor does not begin bogging until well into a trip. Ill keep ya posted. Thanks for the help

 

[jtscudder]

Re: Mercury 25 hp Bogging from idle

I had the same problem with my Merc.25 xd and it was the ball valve connector
that plugs into the tank side of the fuel line.I cut it off and hooked a right angle
fitting directly into the tank with some teflon tape on the threads(be careful not to get pieces of tape into tank or you will have more problems)then I just added a stainless hose clamp over top and it runs like new.I would also recomend changing out your bulb but one change at a time is the best medicine.Good luck.