I will try and make this as quick, short and simple as i can, lol. I have a 2008 Mercury 50 ELPTO two stroke carb motor that I bought with boat brand new 10 years ago. Never had a problem with it until my wife and I had twins so the boat set up for about two years with little to no use. Now I have time to get out and get back to fishing and took the boat out.

-Boat started and idled well with no problem with fresh gas in tank.
-When I applied throttle and got to 2k rpms the motor would start to stutter and sound like it was falling on its face.
-Sounded just like a carbuerated motor should that is struggling to get enough fuel
-while in this stuttering mode at around 2k rpms the tach would bounce from 2k to around 3k but motor didn't sound to be revving near 3k.

-completely cleaned out gas tank again
-replaced plugs
-replaced primer bulb and gas line from tank to outboard
-replaced fuel filter
-pulled the 3 carbs off cleaned them up really good (mild amount of varnished gas but didn't find any real clogs or issues that I thought could have restricted fuel)
-replaced rubber fuel lines that feed fuel filter and lines running to carbs.
-got a kit to replace all the insides of the fuel pump and did so.

Put new gas in her and she started up with no problem, sitting in back yard with lower unit down in a 55 gallon plastic barrel full of water. Idle was higher than normal, bouncing between 1200 rpms and 1800 rpms with a little rough hesitation every 10 seconds or so in neutral.

I did not check the reeds before putting the carbs and everything back together but i have read that the symptoms of a damaged reed will cause fuel to blow backward toward the air box out of the carb. With the airbox off and putting my hand over the carb i cant feel any fuel spray coming back out of any of the three carbs.

I did notice that the bottom carb had a small amount of gas mixed with two stroke oil lying in the bottom of the carb tunnel but not a lot. (is that my sign of it being a damaged reed?)

So with that being said, am i missing anything? Do i just need to adjust the idle on carbs (i didn't touch the adjustment screws during carb cleaning) or does this sound like a damaged reed?

I guess i should also say that when the boat was put up before the two year time period of no use it was running great.

Your help is appreciated!

I am thinking carbs need a better cleaning. If you did a top notch cleaning job then I would suggest adjustments. Can't do those in a barrel. You need the motor to be under a load for that. A service manual for the adjustment prodecure will help alot

Don’t worry about your reeds, they are fine. Sounds electrical from what you describe. I would be looking at the stator or switch box.

Try this, tilt engine up. Remove spark plugs and fill cylinders with sea foam (wal mart). Pour some sea foam into carbs. Put a full can of sea foam to every six gallons of fuel (in your gas tank). Let sit overnight. Next day start and run until engine cleans itself out! You won't believe how much smoke will come out exhaust. Bet it will make her hum!! Been doing this on racing outboards for many many years.

you need to do a better job on cleaning the carbs, were the high speed jets removed and cleaned ? were all the ffuel passages cheched and cleaned ? carbs are the most common problem with an engine that wont run correctly after the engine has been sitting for a long period og time. reeds and ignition will not usually fail from just sitting. you will be better served by totally eliminating the fuel system as the problem first

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This is what I would do first^^^^

I have the same engine on my boat, and it occasionally does something very similar--usually at the end of the day somewhere between 11 and 17mph.

I have noticed that when the battery is charged really well and at the beginning of the day, it rarely happens (check the battery health also) Agree with the prior electrical comment also as a possibility, and maybe the fuel pump?

Im thinking this is probably my problem i have some experience cleaning carbs on small engines and usually do not have to remove jets to get things clean and running right but im going to go through it again. I also didn't remove the idle adjustment screws and i read just a few minutes ago online that I need to do that as well and mark their original spot before removing. I basically just took the carbs off made sure the floats were working correctly and sprayed cleaner through every hole in the carb and made sure flow through those areas was abundant.

I was going to make a one gallon to one can of seafoam ratio and run it through the motor to clean everything but i hadn't heard about pouring seafoam in the plug holes and drenching carbs to soak. I guess this is safe to do since two people have recommended this technique. I just worried about that process since this is a two stroke motor. Im not a mechanic but in my mind i first thought this would wash the cylinder walls from any oil residue that would aid in lubrication once initial start up is commenced.

I also thought my original issue when working on it the first time was due to plastic crumbles that i found in the fuel pump when i took it apart to put in new internals. The plastic pieces were from the little pegs that lock in the little plastic circular diaphrams were setting in the bottom of the fuel pump casing.

I guess its back to getting the carbs fully cleaned but im gonna try the seafoam trick as well.

I would deliver to an authorized Mercury mechanic and let him go through the carburetors. Carbs have many orifices that can become plugged with varnish and deposits.

If your going to run that much sea foam.. i'd certainly run a little extra oil in that fuel to protect the cylinders

I will if I cant manage it myself, but i usually work on my own vehicles, lawnmowers, house repairs etc. Im fairly mechanically inclined and love to learn DIY stuff as well. I already have an outboard mechanic that many friends of mine have used for years that they trust if i cant figure this one out.

I wouldn’t lean on the Sea Foam too much. I know some folks believe it will cure cancer, but to me it’s just a maintenance tool that does have a specific purpose. Have you tried priming the motor while it is bogging? If it is a carburetor issue the motor will respond to the priming. If it does not respond to the priming, look to your ignition. I look forward to the resolution, so please post the fix.

^^^^^^ What he said,....get it done right.

Cleaning a carb is just that, an experienced mechanic will do a very good job at it which most amatuers don't. It just takes time and being thorough. You need compressed air, carb cleaner in a gallon can, carb cleaner in a spray can, some small wire like giatuar string to poke in holes. Take the carb apart completely. Remove rubber and plastic pieces and set aside. Then dip the carb and all metal parts. Let it soak for 15min and blow it out with compress air. Then poke all the holes you can get wire into. Then blow carb cleaner through holes. Reassemble. Simple, not rocket science. Link n sync and adjusting takes more experience and technical knowledge.

If it were me I would leave the idle screw alone. It is easy to clean out on the motor if it needs to be. But first clean the carbs well then test. Setting idle is a whole new can of worms. If you want to, then mark where it sits, screw inwards counting the rotations until it seats itself and mark the seat position. This way when you decided to reinstall it you have an exact starting and end point.

So by "priming" i am assuming you mean squeezing the bulb? I was told when i first started that when its struggling to run, to pump the bulb and if it causes the outboard to respond well and start to take off, that would mean that the fuel pump wasn't doing its job at getting enough fuel to the carbs but that the carbs were good. Early on I went to try this on the lake and the bulb was tight so it made no difference in how the boat ran. I have since then replaced the bulb just because I was replacing a lot of the other fuel system components already. I haven't been back to putting the boat in the lake since this high idle issue has started after cleaning the carbs.

It only trouble shoots an air leak in the fuel system or a bad fuel pump won't do anything if it is the carb. You can use your fimgers to partially choke the carbs by holding them over the carbs intake. If this cause the motor to level out and run smooth, it means you have a carb issue and/or adjustment issue or both.

No, not pumping bulb, hitting the choke/primer. Like Alumacraft said, pumping the bulb only tells you about the fuel pump/fuel supply. I’m assuming you push your key in to prime/choke? Priming sends extra fuel to your intake manifold(behind the carbs). So if you have a dirty carb not supplying enough fuel(this is what causes the bogging or erratic running behavior), priming will give the motor the fuel it needs to take off and run. The motor should “catch fire” when you hit the choke, and it might even take off to full speed once it gets on the main jet. If it does, then you know you have dirty idle circuits and or intermediate jets.

Wow, cant believe i didn't think of that because that makes perfect sense. Restricting air flow to a carb that has fuel restrictions will balance out the air fuel mixture instead of being heavy on air with too little fuel. Thanks! Gonna look it over this weekend as long as the weather cooperates and quits raining.

oh i see what you mean and i didnt even think about that and yes i choke the motor when starting by pressing key in. I haven't tried holding it in while running to assess that yet but will! Thanks!

Don’t just hold the choke in while trying this or you will just bog the motor down because of too much fuel. You want to give it short, quick primes, basically like you are trying to squirt small amounts of fuel in it. Do this until the motor responds to it. It will either run better or get worse.

Ok im back lol. Sorry it took me so long. Life and weather got in my way the last few weekends. Following some peoples advice I pulled the carbs back off to clean again and to try and be more thorough with and I peeked at the reed valves/pedals. Pedals look good, cleaned carb again and just gave her a try. Starts just fine like before but idle seemed much lower than last time. Sounded very similar to how fast it should be running at while in neutral. I say it sounds like its right because my tach is still jumping around like it was and because I worked with the idle and throttle adjustments and if I turn off any more fuel to each carb it starts to run rough. When I say jumping around I mean from less than 1000 to 3500. Stopping sometimes at 2000 for a sec before bouncing back up or dropping down, back and forth. So even adding a little throttle while on trailer sounds good and doesn't cut out or hesitate. All throttle plates are synced and moving like the should. Hard to say how it will run until I hit the lake with it. But with the motor idling consistently with no hits and misses with no surging like it was before, can we say this is an electrical problem? I have read some already on the interwebs about stators or triggers causing these symptoms.

If your tach is jumping around but the motor is at a constant rpm I would definitely say electrical issues

Thanks for giving an update CWCW. You won’t know anything until you put it on the lake and get a load on it. But like my first post said, it sounds electrical. Report back on what it does at the lake. And should you still have problems, remember to try the priming/choking to rule out the fuel system. Stator is a higher percentage failure, would look there first. Triggers are fairly low percentage. Tach comes from the rectifier/regulator, so need to give it a check.

Ok update.... was gonna run and get trailer registration done so I could take to lake and test out. I got to fooling around with looking over the boat again and after reading some stuff online about the rear connections to tachometers getting loose and causing weird readings on the tach I decided to look and all tach wires are good......also read about weird readings on fish finder Voltage while motor running would be signs of stator or voltage regulator issues. Tried to turn on fishfinder and it acts like it has no power, wont turn on. Then I try aerator, navigational lights and bilge pump switches and none of those accessories are getting power to my surprise. I have power to my throttle power trim and tilt and power to trim and tilt button on outboard but no power to any of the other accessories. I have power to the starter. I take out voltage meter to measure voltage and find a resting voltage of 12.3V which is low and it shouldn't be because it had plenty of time to recharge during the last running of the motor and the battery is brand new. Low voltage on battery caused me to look at stator. Found an online Mercury Manual from 1998 for a 40,50,55,60 hp two stroke outboards (mine is a 2008) but the diagrams and everything look exactly the same. Find in the electrical section where it says trouble shooting and I find healthy resistance numbers for the stator. Says Green/White wire to White/Green wire should have a reading from 660-710 Ohms. The multi meter reads 0 ohms and when I switch the red and black multimeter leads to the same two wires I still get 0 ohms. Can I safely say I have a bad stator? Stator has four wires total coming out of it, the other two are yellow and the manual didn't say anything about checking the resistance of those wires so I didn't check them.


I know that this doesn't explain the accessories not working which is a problem I need to clear too but it could be the reason my new battery reads 12.3v and my tach is going crazy.

If you are checking everything correctly, then that stator is certainly bad. Yellow wires are your charge coil, it should have perfect continuity, any resistance there would be bad.

Well I had a few beers the other night when I was using the multimeter and didn't calibrate the ohms dial on the side while touching the black and red leads before I used it. I just hooked the multimeter back up after calibrating it and I got a number of 800 ohms which is over the range that I found online that says 660-710 ohms. Also, after reading PlanoPaul's post above I checked the yellow wires to see if they had any resistance. The scale was at 10,000 ohms one way but when I switched the wires and leads I got no response, not reading 0 ohms, the needle just didn't move. What does that mean? Still pointing bad stator?

check it out for you next week

I did not see this suggestion above. While you are working on stuff, now would be a great time to replace the fuel lines from the tank to the motor. If you have been using ethanol blend fuel, the lines are most likely degraded and possibly flaking on the inside. This can cause fuel delivery issues. I learned the hard way with my 2008 Merc.

Edit: And if my reading comprehension was up to par, I would have noted the OP said he replaced lines in the first post. Carry on...

and while you have the carbs off just go ahead and throw some new needles and seats in them. Over the almost 30 years that I had my Black Max I probably replaced the needles and seats 4 or 5 times. I know some people like to run the fuel out of a carbed motor but I don't. Before you take the carbs off again get a squirt bottle and mix gas and oil in the proper ratio. Pull the air box cover and while the motor is running on a house squirt the mix in the carb intake. Does the engine bog or rev up? If it revs then that is the problem carb. Running a 2 cycle on a lean condition is no bueno. If you spray the mix in to all the carbs and they all bog then probably not a fuel issue. Make sure you replace all the fuel lines with ones that will handle ethanol. The OEMs on my Ranger started flaking on the inside. We found the flakes in the jets.