See full version: How do you adjust the idle on a Mercury outboard motor
Adjust the idle stop screw on the side of the carburetor near the choke cable, turning the screw with a screwdriver until the vacuum gauge is reading about 600 rpm. Turn the idle mixture screw counterclockwise 1/4-turn at a time until you hear the engine begin to stall out, and turn it clockwise 1/4-turn.
Likewise, people ask, how do you adjust the carburetor on an outboard motor? more
What RPM should an outboard idle at? here
The one other observation is that the type of gas seems to make a difference. I'll generally fill up before going to lake/river while boat is still on trailer and its likely that it's gas with the ethanol mix. Later that day while on the water I'll fill up at a marina and I believe the gas doesn't include ethanol, and/or may be a premium (sure costs more). Idle often needs adjusting after a fill, other times no difference.
Things I've tried: (note this was before the 800 mile run last summer)
Removed and disassembled all 4 carbs( I know, only 2 have idle adjust) blew air through every visible passage way, adjusted the floats, put all back together.
Adjusted the idle screws many times, seems like 1 1/8 to 1 1/4 works about the best.
Motor runs well, just doesn't idle smooth, and starts hard.
I have a 2005 115hp 2+2 Merc, probably one of the last one's made, just my luck.
This motor runs great, but starts & idles poorly.
Last year my wife and I put on over 800 miles averaging about 3.5mpg per the GPS on several of the Southern waterways. Above idle, this motor runs great, never a miss, sputter, etc.
The question I have is how smooth should this engine idle? What are the experiences of other owners of these 2+2? Did Mercury make a motor that idled so poorly, or is it just mine? here
Its cantankerous when starting, sometimes at the touch of the key, other times it may take several attempts, never predictable, warm, cold, unpredictable starts. Sometimes it idles good, sometimes(usually) it doesn't. Seems like it runs rich at idle, some noticeable blue smoke. more
All of my questions concern the engine which I believe is a 1983. The serial number is 6263822. more
I am going to assume I know nothing about this engine and so I will perform maintenance as such: here
First of all, sorry if this is the wrong place for this post or my ignorance annoys you.
1. Replace impeller and lower unit oil (with Mercury High Performance Gear Lube SAE 90?). Check condition of lower unit internals.
2. Grease drive shaft with engine spline coupling grease.
3. Grease other things with other greases?
4. Drain gas tank (guy said he took it out last season and stabilized the gas but I'll replace it anyway, he also said he used a 40:1 mixture. I thought I was supposed to go 50:1? I guess since this is an older engine I should go with more oil. Also, I am at 5000 feet. Which gear oil should I use, the guy included a couple quarts of royal purple and one of the mercury brand stuff?)
5. Install an inline water separating fuel filter. Anyone know of a good one? (per Dr. Frankenmerc)
6. Fuel additives such as Star-Tron or Stabil Marine every tank? (per Dr. Frankenmerc)
7. De-carbonize with Sea Foam.
8. Change spark plugs. [links]
give motor info and the problem you are having if you want people to help.
What do you do when you come across a motor that needs to be worked on and which you have never worked on before and have no specific training on whatever it is that needs to be worked on? What did you do years ago when most/all of it was new to you?
ya gotta remember,that Yamaha manual is written for a trained technician not the average joe with a couple of wrenchs and a screwum driver. [links]