my Merc is hesitating…..whadya think?

As you can see by my posts, I’m having all kinds of problems! The Merc is a 2002 115 2 stroke 2+2 motor. When you’re 1800 rpms or below, you run on only two cylinders. Great for saving gas. First question: which two cylinders are running? I’m thinking it’s the top two if I remember right, but not sure.
Basically, the motor is coughing. It’ll chug and miss, but it still flies across the water. But after you fly for a few minutes, a lot of times it’ll go away.

I have a buddy who says I should take a look at the fuel lines and maybe do some replacements as there could be a pinhole in there somewhere. So when the motor’s sitting, air could leak in there, and cause the hesitation. When you get going down the lake, it disappears because the fuel is flowing faster and the pinhole probably isn’t a factor. These are his thoughts, but they make sense to me.

Because of the symptoms, I’m thinking it would rule out spark plugs, and they’re pretty new anyway.
Any suggestions on this one for what I should look at?
Thanks in advance for your answers.

I’m a big fan of having motors checked over every 2-3 years if you plan to own them for awhile.

Honestly, I’d take it to a good dealer and tell them the symptoms. PLUS, check the water pump, plugs, etc. For about 2-300 you can have total confidence for next season. Do it right before you hit the water next year. If your motor is 4 years old, I’d be shocked in the water impeller isn’t already wearing.

Otherwise, it’s air, fuel, spark. In this case it’s probably spark or fuel. Best guess is a carb cleaning or adjustment.

I owned a 95 115 Merc back in the day, it was hard starting and coughed a bit. Had it adjusted and was perfect for a couple of years.

One of the best motors I ever owned though.

Todd

Todd

I wouldn’t rule out the plugs, even if they are new. My buddy has a 135 opti. This spring, with the motor only being about 6 months old, we spent three days fishing and on the third day, the motor started to miss and run like crap at slow speeds. Wide open it seemed fine. By the end of the day, it started losing top end and would barely stay running at idle. Turned out the plugs were fouled. Changed out the plugs and it ran like a top. Changing the plugs is cheaper than a trip to the shop, especially if it works.

Pull your plugs and check them out. Make sure they are “carmel” colored, not black nor frosty white.

If they are black, they are fouled.
If they are frosty white, you are running too lean.

If they are frosty white, check your fuel lines, because you could indeed have a small leak, sucking air. However, if this is the case, it will be difficult for the primer bulb to get hard.

Also, check your fuel filter too.

Also, I believe on the 2+2, the operating cylinders rotate around the 4, meaning that all 4 cylinders fire, but “every other time”.

On 2-stroke, carbed motors, plugs should always be your “go-to” for diagnostics. Especially if you do alot of trolling, for they will foul faster.

had same problem with my 25 this summer and both times it was bad gas–spoke to starks about it and they said they were running in to the same thing about 5 times a week–bad gas or moisture in tank–snagged

I used to own a 125 , I had to replace the fuel jets that open when the extra two cylinders fire. They dump extra gas into the cylinders for takeoff. I had one stick open so it would foul the plugs. If you put new plugs in and it still runs poor, try replacing them. Put both in because one will fail right after the other. I think they cost $18.

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I used to own a 125 , I had to replace the fuel jets that open when the extra two cylinders fire. They dump extra gas into the cylinders for takeoff. I had one stick open so it would foul the plugs. If you put new plugs in and it still runs poor, try replacing them. Put both in because one will fail right after the other. I think they cost $18.

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I have a buddy that had to do the same thing. He does a bunch of trolling which is when the motor is only running on 2 cylinders. Somehow the fuel jets for the cyliders not running got all gummed up and he ended up having to replace them.

Brian- I’m having the same type of problem with my Evinrude right now and I just ordered new plugs. I’m hoping that will fix it. I’ll post the results after I get them installed. Let us know how your situation turns out.

Thanks guys for the replies. I’ll go take a look at the plugs, but I do have a feeling they’ll look all right. The reason I say this is I just took them out and put them on the brush side of the grinder and polished em up real nice. But I’m gonna take another look at them. Might also take a good close look at fuel lines too. I think it’s gotta be in there somewhere. Looking forward to hearing how your motor turns out, Ben.

When you get it all up and running, add some Seafoam to the fuel. This will help prevent any possible fuel problems in the future.

Don’t believe your plugs are good again after brushing them clean on a grinder…..try new plugs, you might be pleasantly surprised. Fishing bud told me his 427/435hp vette only ran good for about 3000 miles on a set. After that he couldn’t pull r’s past 5500. New plugs brought it right back to 6500…..just a thought before you get serious and take it into the shop. He tried all that brushing, blowing and cleaning too…didn’t work

I just got in from taking the plugs out and taking a good look at em. They aren’t white at all, but probably lean towards the black part a little bit. I got another set, so I might try to put those in and see what happens. I also have an inline fuel filter on the line outside the motor so I can see it more easily (plus I needed to have one in front of the Lowrance fuel gauge on the network), so I think I might take the filter out from under the cowling and put a new hose in there. I do still think it’s something simple.

fishhunter,

I owned a 125hp 2+2 Merc and I had this problem about once a year. I had my local dealer “sync and link” the carbs and the thing ran like a top for about a year or a bit longer before I started seeing small coughs and sputters. The cost was not as bad as I thought it would be.

Everyone has an opinion on plugs, but I’ve had better luck with NGK’s for 2-strokes like that.

T

I’m running a 2001 125 2+2, and I second the suggestion to run Seafoam in the tank on a regular basis. I’ve also found that you to have a pro tune and synch the motor once or twice a year depending on how much you use it. When it’s working right, I can stop lusting over a new Optimax/Verado for a few hours.

Well, I replaced a few fuel lines….nothing. I’m thinking it’s gotta be in the plugs (hopefully). I’m gonna take it out either Mon or Wed and see how it does with a switched set of plugs, and go from there. I’m real hopeful that it’ll be this or something real simple, because it was runnin beautifully a month ago. I’m saying wish me luck, because somethin tells me I’m gonna need it.

when you do the plugs, make sure that they have the proper gap in them too. This will help for proper spark and make it run smoother.

Fish, did you get it out one more time after the new plugs?

Hey there, thanks for getting back to me. I’m thinking real hard about taking it out in the early afternoon tomorrow before winterizing it tomorrow afternoon/evening, as I still haven’t had a chance to take it out yet. Looks like our weather is going to take a dump shortly, so I really want to get it out before that happens, but don’t know if I will. I did get some SeaFoam too, so we’ll see what it takes to get this corrected. I’ll let ya know what happens.

Well, my truck is a little bit screwed up, otherwise I would have got up earlier today and taken the boat to the lake before I winterized it. But I guess it’ll have to wait till spring for the run across the lake. It ran real well today, and I did put brand new plugs in it, so we’ll see what happens when I fire it up in March (hopefully).

Good luck in Spring, probably smart to winterize it today with the week’s outlook not very appealing. We’ll look for a post from you in Spring.