Idle problem

[Stump bumper]

I am having trouble setting the carbs on my 2004 115hp Mercury, it won't idle when cold, but does fine after running on plane then after sitting for 10 minutes won't idle again. I have adjusted the mixture and idle control and it just won't adjust out. I just spent $700 on having the carbs rebuilt.

Is there a possibility that replacing the bulb and fuel line to the tank might help? I do notice that when the boat sets for a while I loose the pressure on the bulb and 2 cyl oil runs back down the fuel line. Boat runs great when giving it gas .

Anyone who has had this problem please let me know how you fixed it, really getting tired of the looks at the ramp.

 

[mjk86]

Anything that is rubber/plastic/petroleum based needs to be replaced on the regular imo.  This includes tanks, hoses, and bulbs.  I doubt that will fix your problems...but anything plastic and rubber will deteriorate over time...fragments come off and solid particles cause carbon build-up.  A small piece of rubber or plastic will act as a "seed" and attract partially combusted fuel (also solid/semisolid), which builds up in all the little recesses of the engine.  These build up slowly over time and will gum up your engine, then it cant breathe.  Then it wont idle properly....then people mess with the carb screws even though the problem is engine goo.

All that said....this seems like a question for the guy that you just paid 700$ to "rebuild" your carbs.  He should at least have some suggestions.

[J-Doc]

When fishinwrench rebuilt my old motor, I had the same issue as you.  It took me forever to find it and once I did, it ran great after that.  My timer base was sticking and not advancing the spark which caused it to not idle well especially at the ramp.  It sounds like you have a similar issue.  You’re getting too much fuel and not enough spark at idle.  Which makes it hard to start and idle.

 

Granted your motor is much newer than my old 79 Rude……you could still have something similar to this.  The way I found my issue was to take the cowling off and push the throttle forward (engine off) and checking linkages.  I noticed the idler arm was sticking.  Then I checked the timer base and saw it was not advancing the spark.  Removed the flywheel, cleaned the stupid plastic gasket material OMC designed and cleaned the gunk off of it (grease) and applied an electrical component oil similar to 3-N-1 oil to the gasket and it ran great after that.  I dealt with that junk for 3mo and Glen can attest to how large of a pain in the a$$ I was with relentless text messages and phone calls trying to figure out what the problem was.  And in the end, I still had to take it back to see the doc before I sold it.  LOL!  As far as I know, she’s still running around on the lake sometimes.  Smoking like Tommy Chong at the ramp on start ups and catching crappie.

 

If I were you, I’d check linkages and see if there is a chance that there is something so simple for a mechanical part that is not functioning correctly.  Because if all electronics test out correctly and the carb is rebuilt, it’s something so simple to fix but will be a giant pain to find it.  Then you will get highly upset once you find it.  I know because I almost left mine at Prairie Creek with a sign on it that read “FREE BOAT, I HAVE TITLE, HAVE FUN – CALL IF YOU WANT TITLE”.  And I’m not kidding.  After 3mo, I was beyond mad at it.

[J-Doc]

And to answer your question that I missed above.......replacing bulb may help but I doubt it.  Unless you have a Yamaha bulb on a Merc motor, it's probably fine.  If idle is the problem, I can bet it is something mechanical like I mentioned above.  Not electronic, not carb related.

[fishinwrench]

I'm too excited at the thought of taking in 700.00 on a 4cylinder carb job that I can't process any of the other information you posted.  Seriously though, the job flat rates at 3.5 hr. and the kits are about 65.00 (retail) for 4 of them. That calculates to a shop rate of 180.00 per hour.   I think I'll give myself a healthy raise, effective immediately.  

 

By all means take it back and tell them you are still having problems with it.  

 

 

 

[Stump bumper]

Thanks for the tips, I should have been more clear about the shop I took it to in the spring. They were told just to rebuild the carbs, I had done that twice and thought they were the problem. I told them to leave the plugs alone but of course they put in a $20 set of plugs and charged me $115 and a CDI module that ran another hours labor for a 5 minute job. That is the reason I never took it back, scared if they turned a screw it would be another $500. Of course they said if it wasn't right they would adjust or fix for free, but they lied twice before so I wasn't about to open the checking account for them to clean me out.

J-Doc I will try cleaning everything that is connected to the idle arm but as far as taking it to a shop, I would buy a new boat first.

 

 

[fishinwrench]

Alright, screw the 2 idle mixture screws in until they seat and then tell me how far out they were set.  (number of 1/2 turns).  

Turn them back out 1 1/2 turns and fire the motor up on muffs.   Once warmed up depress the accelerator pump plunger a few times with a screwdriver (it is mounted on the port side of the powerhead)  and tell me how the motor reacts to that (no change, or RPM's pick up momentarily....or does it stumble and act like it wants to die?). 

Then while it is idling squeeze the primer bulb fairly hard and hold it depressed for a few seconds.  Any change in idle speed ?   If no change then push in the key (primer) for about 3 seconds and tell me if RPM's increase or decrease.

If I know all of the above I can probably tell you what needs to be done to rectify the issue.

[fishinwrench]

Oh, and post up a pic of the invoice please.   Cover the name of the place if you want, I just want to cross ref. the parts they sold you.

[Stump bumper]

I will hunt up the invoice and gladly post it with the name of the business on it, thanks so much for the help will drag it out in the front yard and answer those questions tomorrow.

[Stump bumper]

I have attached the repair bill, I hope it comes up. The $500 for carbs I was expecting but a total of $777 because the last mechanic hooked CDI boxes wrong and the motor will not idle right still is what upsets me. That is a total of $1,277 to the biggest Marine repair in town and still not running right on what started as simple adjustments. In fact runs worse than when I started with the first. After looking at the bill, they did more than replace plugs for $190 but I still feel they overcharge for plugs. I should have known to put new plugs in before going there since every mechanic has replaced plugs on me when I tell them I will do that later. They also don't approve of champions in a Merc so I will never take it in to a mechanic like that again.

Repair bill.pdf