Idling issue's on my 2003 90 Horse Mercury

[Rhodes]

I recently bought a Key West with a 2003 Mercury Salt Water Series Outboard. The motor runs good when you throttle it on plane but the thing just won't stay idling. It will idle for just a second and then quit. Isn't there an idle setting on these carbs that may rectify the problem. Before I take it to a boat mechanic I wanted to see if it might be something I could fix myself. Please advise....thanks

[HewesMan]

What are the RPMs when it tries to idle? Sounds like you need to take the carbs apart and clean some jets. There has to be an idle control screw on the throttle linkage somewhere. If the motor has been running the good ol' ethanol fuel, run it as low as you can then only run corn free juice in it.

[charlie tuna]

Run a extra strong mixture of fresh gas and Sea Foam thru it ...

[rockyg]

That year 90 Merc has an idle adjustment knob on the port side. However, I suspect you have partially blocked pilot jets and will need to remove the carbs, clean, soak and clean jets, and reassemble. Running only non-ethanol fuel and keeping some Stabil in the tank will help keep the problem from re-occurring.

[Steve Stinson]

I agree with Charlie T. on the Sea Foam treatment. There used to be a thread someplace on here about how to do it. If you can't find it check http://www.thehulltruth.com and it will be there.

Also a couple of other things to check -

If you have a water separator on your fuel line, replace the canister with a fresh one.

Get a six - gallon portable tank and put a few gallons of fresh non-ethanol fuel in it. Then hook it directly to the motor, bypassing all of your existing lines and filters. If that helps, then your problem is your fuel system. If it doesn't help then most likely it's your carbs.

Be careful trying to adjust the idle. On some of the Merc's you may also be changing the timing or rich/lean mixture which can lead to bigger problems.

Good Luck - Steve

[FUTCHCAIRO]

ITS A MERCURY, WHAT DID YOU EXPECT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
PA
SEMPER FI

[rockyg]

All good ideas Steve. That particular year 90 has a large hand adjustable idle speed knob. It's a carb motor so it won't effect the fuel mixture, and it actually does change the idle not thru the carbs but by advancing the timing.

That being said there is only a very small chance that adjusting the idle will solve the problem. Actually it will probably cause more problems. Cleaning the carbs and making sure you have clean fuel and good fuel system parts is the final answer.

We just worked on that exact model with that exact problem at our shop here in Monticello. While my son and I work mostly on racing motorcycles, the principles are the same in all 2 stroke engines.

[Rhodes]

Thanks guys....all good advice! I especially like the idea to use the separate tank to identify if the problem is in the carbs or the fuel system leading up to the carbs. Just a little more history on the motor. The boat had set up for some time before I bought it. It had approx a half tank of gas in it. we've made one trip and ran at least 20 gallons thru it. I always use stabil and marvel oil at each fill up and also try to find corn-free gas but from what i hear, not everything that is advertised is always what you get? Anyway, I was told by my mechanic to use this marvel oil, he swears by it. I assume it probably has the same benefits as the seafoam but not sure. From what I'm hearing about idle adjustment I am shying away from this. My last motor burnt a piston from an "out of timing" issue so I am very gun shy to do anything that might affect timing. I will put ya'lls advice to work and report back...thanks again.