2003 Mercury 50 elpto

[Daniel048225]

Hopefully someone can help me with my current situation.

Currently my motor idles a little rough and when I accelerate it is also a little rough at low rpms. When I get to about 2500-3000 and up it runs great. I have always run 93 gas and run the boat pretty much every weekend. I have recently replaced the plugs and that didn't help. I am wanting to adjust the carbs but after reading on many forums there are a lot of people that contradict each other and I'm afraid to adjust anything in fear of making it run lean or damaging my engine in some way. If some one could help me with maybe the easiest way to clean carbs with an additive of some type to see if it makes a slight difference or a safe adjustment to try would be greatly appreciated.

 

[Texasmark]

Sounds to me like you need more fuel at the lower rpms which is the low speed adjustment, brass knurled, spring loaded screw on the side of the carbs. Sounds like you have it screwed in too far and you need to start backing them out, ⅛ of a turn till you get what you want or you are 2 full turns out, at which time it's time to look elsewhere. The higher rpms are controlled by the high speed jet which is a fixed orfice and you can't adjust it.

 

[ondarvr]

You can't do any damage by messing with the screws, they only influence the lower RPM range, worst case it runs terrible and you put them back where they were. If adjusting the screws doesn't help you may need to clean the carbs. Additives aren't normally a solution for a dirty carb, but it isn't really going to hurt anything. Try putting your hand over each carb to restrict the air flow a little, if it runs better you found the dirty or poorly adjusted carb.

93 octane is of no value in that motor, you're just wasting money.

 

[Daniel048225]

Thank y'all for your help. I will try adjusting that screw and try a de carb. I'm thinking it is a dirty carb but just too lazy to tear down carbs and clean. Also thank for the tid bit on the 93. I will post and let you know how this weekend on the lake goes.

 

[Texasmark]

Thank y'all for your help. I will try adjusting that screw and try a de carb. I'm thinking it is a dirty carb but just too lazy to tear down carbs and clean. Also thank for the tid bit on the 93. I will post and let you know how this weekend on the lake goes.

If they aren't too bad Sea Foam can clean them up. It also cuts the carbon around the rings and exhaust passages, cleans up the spark plugs, and makes the engine run better, especially on 2 strokers that burn oil with the gas. Either do a "de carb" for a quick solution or put it in the gas and wait for it to work.....all in addition to the tweaking and all mentioned above. Either google or look here in the archives for the decarb process.

 

[Daniel048225]

Okay a little update. During the rush in getting the camper packed and leaving I forgot to get seafoam for the boat. On a good note I went in on the carb screws and it ran great at low rpms but had a cough at idle every now and then. Went back out a half a turn and the cough went away and the low rpm issue slightly came back. I'm gonna definitely try the de carb and replace the fuel filter. I appreciate everyone's input

 

[CharlieB]

1/2 turn at a time is way too much. More like just the width of the screwdriver bladeslot. They are again too fat and need to go in just a bit. Make very small changes and test holeshot.

Ideally you adjust to "Best Idle Speed' while idling around IN gear while IN the water. This is the ideal stiociometric mixture. However the two stroke needs more fuel to accelerate when the throttle is opened so from this Best Idle you open each almost an additional 1/8 turn. Test acceleration slamming the throttle wide open. Any cough, lean miss, or bog is proof there is not enough fuel, so you open each mixture screw that bladewidth and test again. Repeat to perfection.

 

[Daniel048225]

I have noticed one more thing and I know this goes hand in hand but maybe show that I have another issue. When it is in neutral it idles around 1k rpm maybe a little higher. I did try to adjust that a couple weeks ago and got my idle down great but it coughed about every 5-10 seconds so o went back up. With my idle being high it makes shifting harder than I would like in my gears. So from what I have gathered I would think you adjust the carb roller cam to the correct clearance and set your linkage so when you are at wot all three carbs are wide open as well. Then put it in the water and put around in gear and adjust the screws. Would that be accurate?

 

[Daniel048225]

Also is there anywhere on the web to get a service manual to look over. This is my first boat and I'm always learning something with it.

 

[Texasmark]

Coughing is too lean. Also coughing usually occurs without a load as compared to both, has been my experience. Get the SF and give it time to work, like a couple of tanks before you put the Coup De Grace on the low speed adjustment.

Totally agree with Charlie on it taking just a tad here and there on the tweak.....I think you are realizing that fact since you apparently have been on both sides of the mountain and have an idea as to where the peak lies. As I said before, when you get them right, it will idle at around 675 rpm IN F GEAR (set by idle speed screw which varies the timing) with the boat in the water moving, and then when you firewall the throttle, the engine will accept the load and put the boat on plane, not cough and sneeze.