115 Mercury running rich/smoking

[PsYcHo]

Hi, Im a newbie so please bear with me <br /><br />115HP, 6 cylinder Mercury outboard, has been standing 6 years. Previous owner never drained the carbs of fuel before storing. I have drained all old fuel out, replaced fuel line hoses and fuel filter. New spark plugs. Fresh gas/oil mixture (50:1) <br /><br />Starts easily. Smokes quite a bit! All cylinders are firing. Apon inspection of plugs....they have a little oil on them, and what appears to be normal carbon deposits.<br /><br />I have taken the boat out on the water (21 foot speedboat) Motor reaches 5000 RPM but feels rough with the odd hick-up sound. Motor idles a little ruff.<br /><br />So basically it smokes alot no matter what RPM....but the smoke is strong smelling if you know what I mean....unburnt fuel perhaps? Its as though the carbs are not getting enough air! If I disconnect the fuel line and the fuel in the carbs gets used up....it almost runs better/smoother as the fuel gets less just before starving. (If that make sense)<br /><br />So here is my question: What do I do? Is it running to rich? And if so...could that 6 year old fuel in the carbs have clogged up passages? Could I use a carb cleaner to rectify the situation?<br /><br />

 

[Yepblaze]

Re: 115 Mercury running rich/smoking

Pull the carbs, dissasemble, and clean out all the jetss and passageways. If the old gas had "varnished up" it may take some light probing to release any hardened deposits. Here this might be of some value although not model spacific.<br /><br /> http://www.dgweb.com/~bobaloo/Carbclean/CarbClean.htm

 

[Yepblaze]

Re: 115 Mercury running rich/smoking

By the way, some smoke at startup and idle will occur normally. Make sure you mix the gas oil well. If portable tanks add oil to half tank and swish well before adding the rest of the gas. If built in tank add gas, oil, gas, oil, gas, oil, in icrements or add oil to a few gallons in a jug then add to tank along with additional gas. Use a calculator, and keep one handy. Start your equasion with 16 divided by 6 = 2.6666oz per gallon. Be accurate.

 

[PsYcHo]

Re: 115 Mercury running rich/smoking

Thanks Yepblaze,<br /><br />Great URL for a guy who has never striiped a carb before! Stripped the carbs last night-->easy as pie! Surprisingly they were very clean! Save for one of the carbs having a blade of grass (like as in lawn)in the float chamber. Floats look good....no wear on the needles etc. Could see someone had it open before.....damaged bolt/screw heads etc. All gaskets look good aswell, so I guess I dont need to get a carb kit which is expensive around here (around $80 each and I need 3...expensive for us folks)<br /><br />Thanks for your help....will fit the carbs today and let you know how it goes. Only puzzling thing is that the carb only a mixture screw....seems idle is set by the distributor advance. Any idea as to how I should set this one and only screw? Its a WMK-25 mercarb.

 

[Joe S.]

Re: 115 Mercury running rich/smoking

The mixture screw you are talking about is probably the air mixture screw. Gently screw it in all the way until it is seated, then back it out the manufacturers number of turns. The idle mixture is preset at the factory by jetting. The timing could also be present on that motor but I'm not too sure. The best thing you can probably do is get a manual. Good luck!

 

[michaelsen]

Re: 115 Mercury running rich/smoking

Yepblaze, I am messing with a Merc 115hp 6 inline from 75 and just finished the carbs. Turn the screw 1 1/4 turn out and it should work fine.

 

[PsYcHo]

Re: 115 Mercury running rich/smoking

Thanks for all the help! Got her up and running and she feels much better! Just need to check the timing as its not running perfectly yet.