Throttle problem?

I need help!!! I have a 1986 25 mercury xd outboard it idles great and then when i give gas it goes and then dies (almost like its not warmed up). It doesn't want to run at full throttle or in gear for very long. The only way i get it to run for a little bit in gear is when messing with the choke. However, when i put the muff on it with the hose at my house it runs fine and will run at full throttle. I'm guessing that it has something to do with the resistant of the water when running on the lake. Any ideas?

Thanks

The water causes back pressure on the exhaust, and can make them run different. Sounds like the carb needs gone through.

NEVER run the motor at high RPMs on just the muffs. You can cause a runaway situation which can destroy the motor and you. Try it again and whenb it starts to die pump the primer bulb. If it acts like it wants to go, rebuild the fuel pump.

uh,oh sounds like ethanol, very similar to what I had on my merc, carb, fuel lines, filter,rebuild or replace, good luck.

Thanks guys for the info, Okay so i know the bulb is supposed to get hard. On my grandpa's 90 hp when you pump the bulb it gets so hard you cant do it any more. My wasn't getting hard so i went and bought new hoses and ball pump. It pumps up a little harder but not like my grandpas does. Do you guys have any ideas? Do they not get that hard on smaller engines?

You might try using a different gas tank to see if it's the pressure of the tank or try using a different gas tank cap..Thumbs Up

The primer bulb is suppose to get firm when you pump it. After the motor starts it does not stay firm (but not collapse) as there is a suction in it drawing fuel thru it.

Change the spark plugs. you can over pressure the needles in the carbs and cause fuel to run out the overflows. a 90 has more carbs to devide the pressure therefor can pump up harder than yours which is 2 carbs. Best case is that you have stopped up carbs and they need to be cleaned. when you open the throttle the carb gives a small squirt of fuel through a tiny hole on the venturi of the carb which helps the motor build torque to get the rpms rising. with no load on the prop that little squirt isn't neccessary. Under load, it is. worst case is that your motor could be low on compression (if it isn't, it will be if you keep rapping it on the muffs). Change plugs, if that doesnt help then have the carbs cleaned, if that doesn't work, check compression.

Thanks guys for all the help! i had just got the carb done and the guy didnt get the idle screw just right so it wasnt running when i give it alot of gas. I took to the lake today and at first when i was running it it didnt want to run as fast as it should at full throtle. Then after we were fishing for a bit it started up and ran like a top real fast like it should and it puttered for a secound then ran fine. I hope it stays this way do you guys think it was the carb just getting broke in?

thanks again

My mariner 150 was doing the same thing. Had the carbs rebuilt and she runs like a top. My vote goes to carb problems.

Now that you got carb's cleaned out and it is running better I hope you dumped all your old gas and put new in and some marine stabil with every tank full. Are you running any kind of fuel filter on that system?

Carbs don't really break in, but it is possible that a small piece of trash left behind from the carb work or from the fuel system worked it's way through. I assume you have a new fuel filter also? if you haven't changed it, I would.