# Merc 25hp will not run at max rpms !



## RetroJim (Jul 19, 2012)

I have a 2004 Merc 25hp , 2-stroke . My problem has been with this engine since I bought it new . It will start fine , idle fine and run 1/2 throttle fine and that it !  The rpms will not go any higher than about 50% . The throttle is open wide , carb throttle is also open all the way , carb was just  rebuilt , new pump bulb for fuel tank , cleaned the carb filter & fuel tank filter . New spark plugs installed . Fuel tank connections are all good and tight . Coils are fine as well .
I only used this engine maybe 15 gallons over the last 6 years . I bought it new and didn't run really well to me at that time . Just figured it needed time to break in .
I did use new 2 stroke oil in the fuel along with Sta-bil Marine . 
The one and only time it ran full rpms was last month for about 1 mins then started dying at full throttle . Then I would take out of gear and it would start right back up no problem . This went on for about 20 mins or so untill it got to the point of not starting at all .
After a crb rebuild it seemed to run ok but only at about 50% of the rpms it should be running at full throttle .
Right now it will start and run just fine BUT will only rear 50% of the rpms the engine has .
I am starting to wonder if the "reeds" were bad from the beginning . That is the only thing I can think that might be causing this problem .

PLEASE HELP !

Jim


----------



## Brett (Jul 16, 2008)

I had an outboard that no matter what I did, it wouldn't produce full rpms.
I knew compression was good, spark was good, fuel pump was good, intake vacuum was good,
I finally just replaced the entire carburetor with a new one, solved my problem.


----------



## cutrunner (Jun 8, 2010)

Turn the primestart off!! Lol just kidding


----------



## DuckNut (Apr 3, 2009)

Do as Brett said or try to find someone who has a set of carb jet bits and have them clean and check the jets.


----------



## anytide (Jul 30, 2009)

shoulda took it back!! 
-a


----------



## Sheremeta (Nov 29, 2010)

did you check compression? You could try to spray mercury tuner or seafoam deep creep in the jets.


----------



## AfterHours2 (Aug 2, 2010)

Had the same issue on a Yamaha. Replaced endless parts. Do as Brett said and just buy a new carb. That's the problem altogether...


----------



## Rediculous (May 5, 2012)

I have the same exact engine, that had the same problem. I replaced the pick up tube in the tank and all the fuel lines and bulb, cleaned the carb a little and she has ran perfect ever since. I didn't have to buy a new carb, maybe you don't either.


----------



## islander1225 (Jun 15, 2008)

I'll give ya 500 bucks for it and then you have no more headaches lol.




Alex


----------

