Rough Motor Help!

Hey Everyone!

I have a 2004 125hp 2 stroke mercury classic motor on my crestliner. The motor when moving works great, but sometimes it’s a @&$!? To get started.

I only run regular gas in it. I have read some stuff about seafoam working well and also some people out premium in their boats…

Any advice? Heading up north Thursday so if there is any “fixes” I’d like to knock them out today if at all possible!

Thanks!!!!

I’ve got that same year Mercury motor, but much smaller. I always use non oxy gas and that seems to work well. And I use SeaFoam. Can’t hurt. If I were you, I’d dump some SeaFoam in and try it. Cheap fix – if it fixes it.

Cold starting issues are generally related to not enough fuel or too much fuel.

I would hold off on adding a bunch of goop/snakeoil to your fuel as that could make the issue more difficult to diagnose and at the very least it’s unlikely to help this issue. Detergents like Seafoam will only help for a narrow range of problems with varnish in the fuel system, they are not a cure-all.

Verify if Merc still had the electric choke on the 2004 models where you push in the key while cranking to set the choke? I didn’t look it up, but this would be my leading suspect.

1. I didn’t look it up, but if it has an electric choke, check that the choke is setting while cranking. You have to verify that this is the case with a cold engine as something may be binding just when the engine is stone cold.

I would use carb/choke cleaner to make sure nothing on the carb is binding.

2. Check the fuel hose for air leaks. The best way to verify if the hose is the problem is to swap it out for a different hose. You can’t just casually look at the hose becaue an air leak can be very small and hard to see other than a slight stain on the hose from fuel leaking.

Also check to make sure your ball on the fule hose is working properly and is holding pressure. I’ve seen these go bad where you feel them come up to pressure, but then they quickly leakdown. Make sure the ball stays firm when pumped up.

3. Are your spark plugs good? Have you checked the gap? Yes! You must, must, must use the proper gap and NO, .030 is NOT the universal gap setting. There is no such animal as a “universal gap setting”. Look it up and set it accordingly.

4. Use a spark tester to check each plug and make sure it’s firing. If you don’t have a plug tester, spend the $10 and buy one. Do each plug, one or two is not good enough. Make sure you have spark on all jugs.

Grouse

Is it always a hard starter? (Cold start and warm start) Are you engaging the key choke when trying to start and re-start? Are you leaving the motor in the neutral position? Have you tried pushing in the reverse disengage and giving it a little more throttle while starting? Is the primer bulb pumped up hard prior to start?

-J.

Thanks man!

I will start trouble shooting.

Plugs are new and gapped. I do have an electric choke. How do I make sure it is set correctly?

I always have to give it throttle to start.

When it’s cold it will fire up with the throttle engaged but usually it runs for a few seconds then dies. I make sure the ball is hard and try it again 3-5 times then it runs. Usually when I put the throttle back to neutral/attempt to reverse or throttle away for the dock, is when it kills.

Once it’s no longer cold, it fires up right away.

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I’ve got that same year Mercury motor, but much smaller. I always use non oxy gas and that seems to work well. And I use SeaFoam. Can’t hurt. If I were you, I’d dump some SeaFoam in and try it. Cheap fix – if it fixes it.

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X2

That motor doesn’t have a choke, it has an enrichment solenoid. Sounds like you just need to find the starting sequence this motor will like best (I have the same one). Give a little throttle, start cranking the motor and while the engine is turning bump the enrichment. Continue to bump the enrichment to keep it going once it starts. I also worked on my idle jets to get a good smooth idle out of it. They are tempramental when it comes to starting but I have never had it not start. I also only use premium non-oxy fuel and no other gunk added to it.

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They are tempramental when it comes to starting

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This is true. Seems most all of those 125 2+2 motors are cold blooded.

-J.

What do you mean by bumping the enrichment?

Just pushing the key in and out? Do you hold the key in when you start it up?

Yes, push the key in and out. No I don’t hold it in, too easy to flood it this way. This enrichment system bypasses the carbs and dumps fuel directly into the crankcase. It is run off the fuel pump pressure and not vaccuum pressure through the carbs.

Awesome I will play around with this. Thanks everyone for all your help!

the big problem is that the carbs have to be horizontal so tilt the motor so that the carbs are horizontal then prime the motor by pushing the key in about 6 or 7 times hold the key in and try starting it give it a little throttle it should start easy then that has been the trouble on the 3 cylinders too they need fuel to get them to fire

Pushing the key in without the engine turning does nothing, there is no pressure in the system to get fuel into it. But if it makes you feel better go for it, kinda like fishing it’s a confidence thing. A google search for the starting procedure on this will also help if looking for advice but most are pretty close to the same.

Skip the seafoam, I use it alot for everything but won’t fix your problem… motor should be horizontal when starting… Some mercs were famous cold starters… Keep that battery fully charged too! you may have to run it on the warm up lever quite a bit… Check all your fuel lines for dryness or cracking… Run eth free gas if posible…