Please help! I'm ready to throw my Mercury 5hp in the lake!!

Ok so I really won't throw it in the lake. But I have spent a good 10 hours or more and still can;t get this 5 horse running. It is a 2005 model and has not been used a lot. I purchased it 6 months ago from a guy and it was running fine. I probably should have put fresh fuel/oil in it but didn't. Started having trouble starting it so I put in fresh fuel. Problem is I put the wrong mix and put in way too much oil. After realizing I did this, I decided to go ahead and clean the carb. When I took off carb it was VERY clean. Motor still seems like new. I cleaned it anyway and put it back together and added fresh fuel/oil. It took a lot of pulls and a few times would spray some fuel inside the spark plug, and FINALLY I got it to crank. I ran it for a good 20 minutes and so I thought it was finally fixed. Took it to the lake and ran it around, then it died on me, and now I can't get it to crank again. Spark is good, crab is clean, fuel line is clean, water pump works - so what should I try now??? Any advice would sure be appreciated! I'm not that mech inclined so please be detailed. thanks!!!!!

You probably messed up the carb settings. Stick it in a barrel--prop off--and pull the plug(s). Clean them with lacquer thinner and--while they're out--pull the motor over a few times to blow out the oily gas. Next, install the plugs and get her running--you might need a shot of ether to do it, but avoid that if you can. (If she's really loaded up with oil, you might have to repeat the above a few times.)

Warm it up at high idle, then slow it down as low as you dare (without stalling) and find the best idle adjustment. Then add 1/8 of a turn CCW.

Jeff

Thanks Jeff! When you say 1/8 turn, are you referring to the little screw on the side of the carb that has a spring on it? Is that for adjusting the amount of air that mixes with the fuel? Do I start with it screwed all the way and then loosen it slightly? Last question: There is a little box on the side of the carb (the fuel line goes into it). I'm assuming that is the fuel filter or fuel pump? When I took off the carb I also took that apart and put it back together. I think it is back together okay but it was tricky because it had real flimsy black sheets inside and it was hard to get them to stay flat and stay in place. Do you think this is part of the problem? Maybe it got messed up when too much oil got in it, or maybe I should not have taken it apart??? What are your thoughts? Thanks again!

JSG that box sounds like your fuel pump. If that was bad I doubt you would have gotten it to start in the first place, but you may have gotten some trash in it now so you might clean that as well. as for the adjustment screw, Turn it CW until you get it to seat lightly, then back it out 1 1/2 turns. Once you get her started you can turn that CW and CCW slightly to see where it idles the best. Once you find that spot, back it out another 1/4 turn and you should be good. Are you running a remote tank? If so that could also give you a problem. Let us know.

I have a remote tank and an internal tank for it. Right now I'm just using the internal one. I tried to crank it again today with no luck. Tried to adjust the screw to different positions but could not get it cranked. Isn't there some way to force it to start and at least run for a couple minutes? I think a couple weeks ago I got it to run for a few minutes by pouring a little gas in the hole where the spark plug goes (and then re-installing the plug of course). Is that a bad thing to try?? I feel like if I can just get it cranked, then I can adjust that screw until I find the sweet spot. Then again there could be a totally different issue that I'm unaware of. Frustrating because this motor is like new and should run like a top!

If you got it to fire by spraying gas in the cylinder then it sounds like a fuel issue. You may have to pull that carb again. Make sure your float is working properly. You can check this by turning the carb over with the bowl off and blowing into the fuel inlet. move the carb up and down with your finger to make sure its opening and closing at the needle and seat. If you set the idle adjustment screw like I suggested and your getting fuel into the carb it should fire. if you use the remote tank you might be able to force fuel into the carb by pumping the bulb and if it starts and you can keep it running by continously pumping it then I'd suspect your fuel pump. You might even try that first before pulling the carb off again.

Need serial#s,mod# etc.Profile???
Start by rebuilding the carb/fuel pump.That flimsy black sheet is the diaphram.Any streching or holes and missing springs will do what you are experiencing.REplace all the hoses.Any inline connectors? They can leak and suck air.
Air screw in LIGHTLY to the bottom,you can damage the taper and it will never work right..Out 1 turn.Final setting should be done in the water.
While the carb is off check the reeds for broken missing reeds.New plugs.Make sure the fuel is correct/no water.Starting fluid strips the oil away so use it sparingly if at all.A spray bottle with oil/gas mix will do as well.Do these things and post your results.Jerry

ok fellas, here is the latest. I just took off the carb again. When I got it apart, I noticed the screw in the middle of the float was very loose. I assume it was not supposed to be this way?? Could that have been the problem? the float itself looks to be fine and falls freely when turned upside down. I don't suspect it is sticking, and everything else about the carb looks perfect. I hope to get out tomorrow and see if she will crank. Hoping that loose screw was the issue (maybe allowing too much air in?? Let me know if that screw was supposed to be loose like that. I am also going to put in a new spark plug for the heck of it. The current one looks fine and I tested it and it is sparking but I'm not sure how big the spark is supposed to be (pea size or marble size??) also, should I start out with the idle adjustment screw tight or loose? what is a good site to buy parts for it? I may go ahead and buy a new diaphram as well because I may have messed it up when I took it apart.

disregard my question about where to buy parts. I totally forgot this site has them! ha!

The spark should jump about 7/16" Idle adjustment and air screw,two different things.Air screw out 1 turn.The only thing moving in the carb should be the needle/float.The fuel pump on the side,the diaphram is the only thing that should move.J

Couldn't find how to post a new question but here it is. My 2005 Mercury 4 stroke is also about to go in the lake. When I started it the first time this year it obviously needed the carburetor cleaned, a $400.00, 2 month process at the dealer. I changed the fuel filter and removed the carb and cleaned it. Replaced it and it started easily but WILL NOT REV to its normal rpm. Bought new carb and installed with a new filter. Exact same problem. Is there a high speed carb adjustment on these? The screws for what I believe are the jets were screwed all the way in on the original and also on the new carb. I tried backing the screws out but it is obvious that they are meant to be screwed in all the way as gasoline leaks out after the screw is backed out 1 1/4 turns. Squeezing the priming bulb on the exterior tank while the motor is running does not help the low rpm problem. This old geezer would appreciate some help.