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2004 Merc. 25 hp , Only about 50% power with throttle open 100% . Please HELP !

R

RetroJim

New member
I have a 2004 Mercury 25hp , 2 stroke tiller electric start that I bought new in 2005 . I was told to run the fuel mix 2x the fuel/oil ratio*for the first tank of 5 gallons for break -in . I did about 8 gallons to make sure . Now as I was using the engine it just didn't seem to be making full power*for a*25hp engine .* I got hurt and didn't use the engine but a few times over the next*5 years BUT did run the engine now and then with water hooked up to the lower unit to keep everything in good condition .
Well this year I got the engine ready with NEW Quick Silver oil , FRESH fuel and took the boat to the local lake to fish . Well it starts up just fine , idles fine and is good for about 50% throttle even though the throttle is open 100% .* One time the engine did run very nicely and the boat was very fast !* I was very happy that the engine was running very good finally !** That was the one and only time that ever happened or ran that good .*So I called up 2 seperate Mercury dealers and both told me it's "fuel delivery problems ". So*I told them I installed 2 new spark plugs , cleaned the fuel filter , bought new oil and fuel , I also cleaned the fuel tank out and also cleaned the fuel filter in the tank . I also replaced the bulb that you squeese to get the fuel up to the engine and checked the fuel lines and all was new and clean !*
So I asked them what the problem should be ?** They both told me I had a bad fuel pump probably from sitting . So I bought a new carb kit from*the dealer and rebuilt the carb .* This was my first carb rebuild on an outboard*BUT I*have been rebuilding auto carbs and engines for a very long time . So I am not*a total blank when it comes to engines .
So after the rebuild and making sure everything was very clean and nothing was clogged in the carb anyplace , I*put everything back together and pumped the new fuel and oil mix into the freshly rebuildt carb . It started right up and sounded just fine . So off to the lake for a test run . Well the same thing happened . It's good for about 50% throttle even though the throttle is open 100%*and I*can't get anymore RPM's out of the carb* no matter what I did !
Now this is a basically a NEW engine with maybe 25 to 30 gallons of fuel through the engine . It also has only run 100% for about*5 mins one day until the engine would cut out . Then I would put into nuetral and hit the starter button . It would start right back up with no effort at all . Then off I would go until about 30 sec. , then the engine would stop again . This went on for about*15 mins until it wouldn't start and run anymore . I used my electric motor to make it back to the docks .
Like I said , the engine never really ran 100% from new but that was my engine for the local lakes . I thought it would run better once the engine was broke in really well !* I had a 40hp I used most of the time on the river and*other lakes*. I since sold the big engine 2 years ago and just went to use just the Merc. 25* engine since it was basically new .
I have looked all over the internet and tried about everything to get the engine to run a full 100% but can't figure out what is wrong with the engine . I do know that the carb is fine since I have taken it off 3 times and checked everything to make sure I did it the correct way .* Even the gaskets looked fine to me BUT I did replace them with the NEW kit anyway !

I did read someplace about the "Reeds" and getting racing reeds . What exactally do the reeds do and could these be the problem ???

I*really hope someone has an idea since I can't afford the cost of the boat dealer plus wait 2 to 3 weeks before they can even look the engine over .

Sorry for the very long post but I wanted to make sure that I covered everything that is going on with the engine since I bought it new and everything I have checked and replaced so far !
It's very upsetting since the engine is basically new and only has maybe 4 (5 gal.) tanks run through the engine so far !* Being on disability really sucks with no extra money and now an engine that won't run right .

Thanks ahead of time for everyones help with my engine problems !**

Jim
 
Thanks for the reply but I have no idea on what you are talking about . I looked on the link you posted but still have no idea on the parts you are talking about .
Like I posted the engine is basically new so it shouldn't be having problems like it has . I have tested the coils and they are fine along with the other items I have replaced from what the boat dealers told me to go through .
The only thing I can figure out that is has to be something that the ethanol fuel we have to use has caused someplace along the line but not sure . I did run great for about 5 mins since I have owned the engine and that's it .
If you can explain to me what the trigger and stator is that will be helpfull .

OK I have read that page again and I don't know what the 2 things are . BUT as I read it , it say about missing , cutting off and things like that .
I DON'T have any problems like that at all ! The problem I am having is it WON'T HIT FULL RPM'S AT FULL THROTTLE !

Thanks for your help !
Jim
 
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I did check those along with all the wiring & connections and all checked out fine . Nothing got inside and both gave good spark . Was some of the things I checked over .
It just runs like I am dragging a 1000lbs through the water and it just won't get the RPM's up past 1/2 throttle for some reason . The carb was super clean as well . I didn't go past the carb into the engine so if there is something that could be wrong , clogged or stuck in there , please let me know . I have owned Mercury & Mariner engine for over 25 years and never had a problem with them until this engine . I have also adjusted the fuel/air mixture as well with no luck .
It really never ran full out from the beginning . Then when I got hurt and didn't use it the warrenty ran out . Now they wat $79 just to check it over to tell me what's wrong with it and right now I don't have that kind of money for that plus it will be 2 or 3 weeks before they can look at it !
Now I am wondering if something behind the carb is clogged up and gumbed up due to the ethanol fuel .
I am also using the Sta-Bil Marine fuel additive too .

Thanks ,
Jim
 
Something tells me you're loosing a cylinder under load. Try a plug test: Run her wide open for a few minutes (under load) and shut it off without any idling time. Then pull plugs and take a look. If one of them is cold and oily, you might have a bad coil--seen a few of them lately.

Don't zero in onte ethanol issue so much: you might be tricking yourself.

Jeff
 
True but it ran really good that one time then just died and shut off like it wasn't getting any fuel . Then it would start right back up and keep doing the very same thing . Then each time the engine would run less and less time till it wouldn't run at all ! Then I rebuilt the carb , installed new spark plugs and cleaned all the filters and fuel lines out . Then it was back to running the same way at about 50% power .
Now it will just run just fine about 1/2 throttle and then when you open the throttle wide open , there is no change in the engine RPM's at all ! It just runs like you have just 1/2 throttle no matter if it 50% open or 100% open throttle . i am really stumped on this one .
it's like in NASCAR when they use a Restrictor plate under the carb to keep the RPM's and speed down so the cars can't go as fast .
It also drings fuel as well . I went through over 2 gallons of fuel for about 8 hours of just trolling at my local lake fishing . I also checked the new spark plugs and both are even color and not oily .
Can you tell me exactly what the reeds do in the engine ? Someone said something about them on another fishing form I am on .
Eliminating differnt things will finally find out what the problem is I hope !
Thanks again for all the help in trying to figure out the problem of the engine not running full power .
Jim
 
A couple of questions to clarify things:

1. At your "50 % throttle" does the motor rev up high? If so, the hub is slipping.

2. You said that you checked th eplugs, but have you run my full throttle, kill the motor immediately and pull the plugs test?

Jeff
 
Coil packs are fine and attached .
Prop is tight and fine also .
Like I said the engine ran great the first time I took it out this year . Boat was running a staedy 25 mph . Then the problem started all over again and now I can only get 10 mph open wide . The engine doesn't get the rPM's up very high like it should when the engine is open wide . From 1/2 throttle to full throttle , there is NO dofference in the RPM's or MPH .

Jim
 
RetroJim: I'm w/fastjeff. Clean the spark plugs then run the WOT test and read the plugs. If that pans out good then I think you need to revisit cleaning the carb. "it looks clean" means nothing. Spray pressurized carb cleaner for several seconds thru all of the passages exp. the high speed jet and then blow it out w/100 psi compressed air. It ran good once before which could mean there is crap floating around in the carb restricting high volume fuel flow.
 
I actually did the WOT test on the water one day with new plugs to see what they lookd like . Both were nice and both were equal in color .
When I did rebuild the carb I used carb cleaner in the tiny passages and the jet I did clean but was very clean to start with but cleaned it anyway . Everything came out OK and nothing "Nasty" or anything like that came out . I even checked the 2 coils while the engine was running , to make sure that wasn't the problem . The first one bit the heck out of me and the other one sparked just fine .

Now this has run like this way (50%) since I bought it but I never really used it because I have a 40hp main engine for all the water I fished on . When gas got real costly I didn't make that 2+ hour drive anymore to the places we fished using my 40 so I sold the 40 to just use the 25hp . This 25hp runs about the same as my Mariner 15 hp I use to have . That's sad .

Anyway Like I said , the engine ran GREAT the first time on the water this season ! I was very happy with it until for no reason it would die out . Then it would restart right away and off I went but when I hit full throttle it would die out again after a few seconds .
So I took the hood cover off to take a look . I always carry tools with me along with a set of new spark plugs so I pull both spark plugs to take a look . They were both very clean and equal in color . The fuel filter was clean and full of fuel too . I cleaned the plugs a installed them . It started right up and idled fine . Fuel filter bowl was full . The fuel bowl would go down about 3/4 then fill right back up . So I know the float is working fine and the needle valve is working like it should be as well ! So with the cover still off , I put into gear to see what happens . Well it ran fine and even at full throttle , then all of a sudden , it would just die out again after about 10 seconds .

Now I did watch the fuel filter bowl that is before the carb and it almost ran dry at FULL throttle before it would fill up again . So that is why I was assuming the fuel pump was bad from sitting and due the crappy fuel we have to use . I also made sure the throttle was open full too ! I even tried running the engine by using my hand to work the throttle on the carb just in case the cables weren't opening the throttle all the way . I was just trying to cover all the bases before I took the boat in .

I did remove the spark plugs and installed a new set that I always have on hand . The engine started right up and idled just fine . I gave it some gas and seemed to be running fine so I gave it full throttle and the boat took off great . Then it died once again so I removed the new spark plugs and put the old ones back in . The new plugs looked fine and didn't have any bad color or anything like that .

Well that is when the engine really started getting bad . It would start but wouldn't run but for maybe 30 seconds then die out . With in 10 mins. , it got to point that the engine wouldn't start no matter what I did ! It had plenty of fresh fuel too ! I ended up getting the boat back to the boat launch with my electric motor . That is when I contacted the 2 boat dealer and they both said "Fuel Delivery Problems" . I told them I replaced the spark plugs , clenned the fuel filter and used new fuel and new oil . That's when they both said , "It sound like a bad fuel pump" . So I got a new carb kit and rebuilt the carb and cleaned it even though it was very clean to start with .

After that it run all the time with no problems starting it and no problems with it dying out on me . I used that engine trolling for 6 hours and ran just great in 98 degree heat . BUT it still wouldn't go but maybe 50% of the RPM's it should be doing no matter if it's 1/2 throttle or full throttle .
I am totally discusted with this engine since I have not used it engough for something to go wrong with it .
It's just never ran right since I bought it and only ran great this one time this summer when I took it out for the first time this year .
I have been building street engine to full blown race engine for many years , rebuilt enough carbs to last anyone a lifetime and have been doing this since I was 16 years old . I am 58 years old now ! I worked as a mechanic for many , many years and have never , ever had an engine like this one that I can't figure out what the hech the problem is . I am disabled now and still rebuild engines and carbs on the side !
It just seems like it's not getting all the fuel to the cylinders like it should be doing .

So I am really wondering if there is a restriction AFTER the carb to the cylinders . What is in between the carb and the cylinders that would deliver the fuel to the spark plugs . Cars have a manifold so I am wondering if something is wrong that is between the carb and the pistons that is not letting the fuel/air get there so the rpm's would go up .

I have checked , double checked and tripple checked everything that goes from the fuel cell to the carb to the plate that the carb mounts to .
So my thinking is maybe someting after the carb plate is causing this problem .
Any thoughs on this maybe being the problem ????

I am a good mechanic when it comes to American cars but this has really got me stumped right now .
I do really appericate all the GREAT help from all of you and the "Teaching Lessons" that you are giving me ! I have had plenty of New and Used Mercury and Mariner engines and swear by them ! I have loved everyone I ever owned EXCEPT THIS ONE ! The ONLY other engine I have ever owned was a older Johnson I had as a kicker engine for trolling that came with a used boat I bought and it was a good engine too but I have just prefered a Mercury or Mariner engine over the others .

Thanks again for everyone helping me to figure out what the heck is causing my engine not to hit full RPM's !

Jim
 
I did watch the fuel filter bowl that is before the carb and it almost ran dry at FULL throttle before it would fill up again.
Click to expand...
Figure out why...have you tried a different fuel tank?
 
That was happening when I started it up for the first time this year and when I took it out on the lake . At full throttle when it actually ran great , the fuel would all but empty that fuel filter out before it would fill back up again . I will assume the needle was sticking at that point or was a bad fuel pump .
After the carb was rebuilt , I don't have that problem anymore . It stays pretty full all the time once it gets 1/2 empty .
I fuel tank I have is the only one I have but I checked all the lines , replace the primmer bulb , check the filter in the fuel tank and everything is 100% . I also check the vent valve to make sure nothing was cloging that as well . Everything there was fine .

I am stilll wondering if there is some blockage after the carb . I am not sure how the fuel gets delivered into the cylinders once the fuel comes out of the carb .
Any suggestion on that end would be helpful . If someone know of a link that will show all those parts I would be greatful . I would buy the repair manual but wow , they are costly !

Thanks ,
Jim
 
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guyjg , Thank you very much for that video . That explains a lot of things to me .
I know things have gone wrong before and just because it's new doesn't mean it was built correctly BUT is it possible that the reeds might be sticking or gumbed up from sitting and not opening all the way to let all the fuel and air through thus not letting the engine run at full RPM's ? It does use a lot of fuel . I did use it for about 5 to 6 hours of trolling close to the boat launch and used over 2 gal. of fuel almost 3 gallons .
Could this be an issue to consider ?
Would it be advisable to remove the carb and clean it out once again while it's out , but remove the plate behind the carb to inspect the reeds and see if they are sticking or gumbed up ? I never ran any carb cleaner while the engine was running so i am not sure if this could possibly be an issue or not .
Since it's been like this from new Except for the one and only time it ran goo that day , could the builders maybe have installed the in correct reed and installed stiffer ones that a bugger engine would get ?
If that is possible then that would make the engine not be able to get enough air in the carb to make the reeeds move more so in turn the RPM's would go up and right right .

Just thinking this through to figure out some things that could possible cause the problems I am having .

Thanks again for the video on how the 2 stroke works !

Also off on another subject , can someone tell me how the Spell Check works ? I click on the ABC but nothing ever happens . I use it all the time on other forums but this one doesn't work for some reason .

Jim
 
RetroJim said:
guyjg , Thank you very much for that video . That explains a lot of things to me .
I know things have gone wrong before and just because it's new doesn't mean it was built correctly BUT is it possible that the reeds might be sticking or gumbed up from sitting and not opening all the way to let all the fuel and air through thus not letting the engine run at full RPM's ? It does use a lot of fuel . I did use it for about 5 to 6 hours of trolling close to the boat launch and used over 2 gal. of fuel almost 3 gallons .
Could this be an issue to consider ?
Would it be advisable to remove the carb and clean it out once again while it's out , but remove the plate behind the carb to inspect the reeds and see if they are sticking or gumbed up ? I never ran any carb cleaner while the engine was running so i am not sure if this could possibly be an issue or not .
Since it's been like this from new Except for the one and only time it ran goo that day , could the builders maybe have installed the in correct reed and installed stiffer ones that a bugger engine would get ?
If that is possible then that would make the engine not be able to get enough air in the carb to make the reeeds move more so in turn the RPM's would go up and right right .

Just thinking this through to figure out some things that could possible cause the problems I am having .

Thanks again for the video on how the 2 stroke works !

Also off on another subject , can someone tell me how the Spell Check works ? I click on the ABC but nothing ever happens . I use it all the time on other forums but this one doesn't work for some reason .

Jim
Click to expand...
I have the exact same problem as you!!! I have replaced all the things that you have and done everything you have but my motor will only go 50% of its speed at full throttle!!! My motor is an 05 25 2stroke mercury.
Did you ever figure out what was wrong with it
 
Yes I did ! About 2 weeks after all this crap and nothing still working , I came up with the conclusion that it had to be the REEDS not working just right . Well after using about 6 gallons of fuel and adding 2x the amount of Marine Stabil in the fuel and using ONLY Quick Silver 2 stroke oil , all of a sudden it started running GREAT ! The damn REEDS had to be getting stuck for some reason . I can't think of any other thing that it could have been . That was the ONLY thing I didn't replace either . You also have the same year Mercury 25 I had too ! It must have been a bad run of reeds that were getting stuck and not working all the way .

Actually I was getting ready to order a new set of reeds when a friend asked about taking him fishing the next morning . I told him we can use his boat but it's only a small 10' with a 28lb electric motor . So I told him mine isn't running 100% yet but it would be bigger and a lot faster than his will be so we will take mine out .

So we launched and started out of the cove . I have the throttle wide open as usual then he turned and looked at me and said , I thought your engine still wasn't running right ? At this time the RPM's were still climbing and we were at 21 mph at this time and still pulling strong ! We topped out at 28 mph and was moving right good across the small lake we fish at . I have a Alumacraft 165 full of gear and 2 adults with an electric 55lb up front and the 25hp Mercury on the back . So it isn't a light boat like many other that are used on the lake .

The engine starts right up very fast , idles great at low rpms and still runs great ! I can't say 100% sure that the reeds were the problem but if I had to bet on what the problem was wiith the engine , I would still put all my $$$ on the Sticking Reeds being the problem !

Now this has been at least 21 gallons of fuel ago ! I have been out many times since then and it's still running great . I am thinking about changing the prop to a smaller pitch to get the boat to move quicker out of the hole . I changed my last 15 hp. Mariner 3 blade prop to a 4 blade prop and it jumped very fast from a idle and still went just as fast as the 3 blade prop did . Just got it up to peak rpms much faster .

Anyway , just remove the carb and that bigger plate that the carb bolts to and the reeds are behind there . I would consider using some carb cleaner first down through the carb air vent and that just might get them working OK . Do this while on the water or having the engine in a big container full of water to put pressure on the prop , just like if you were out on the water . If that doesn't work , you can order new REEDS off the internet a lot cheaper than the local Mercury Dealer ! I honestly think the reeds were stuck from the factory for some reason but can't say for sure . It just never ran right from the day I bought that engine but the dealer told me to give it time to break in . I guess it was a bad batch of reeds they were using . I still swear by the Mercury/Mariner engines and always will ! I have owned many of them and love them ! This was the First and ONLY one that ever gave me a problem ! AND YES , when it's time to replace my 25hp Mercury for whatever reason , I will buy another Mercury or Mariner motor again with no hesitation either !

Let me know how you make out with your engine .
GOOD LUCK !

Jim
 
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