Outboard motor running rough

[Born2fish]

I have a 115 mercury. It's a 98 model. Here recently when I start it, it idles rough and shakes. Several times when I go to put it in gear it will die and it will take a few times before I can actually take off. Any suggestions???? Thanks a lot!!

[Embrey]

I have a 115 mercury. It's a 98 model. Here recently when I start it, it idles rough and shakes. Several times when I go to put it in gear it will die and it will take a few times before I can actually take off. Any suggestions???? Thanks a lot!!

need a lot more info or you will just get a bunch of guesses. what does it do when warmed up?

[Born2fish]

It does it no matter if warmed up or not. I can fish a 12 hour tourn and everytime I take off it runs rough. Once I get it planed out it runs fine. But I turn it off, and start it up and put it in drive it dies. And when it idles the outboard shakes

[Embrey]

start with the basics. tune up,and check compression,fuel flter,etc. are you sure its firing on all cylinders when planed out?

[HURRICANEBOB]

If you have a set of water muffs at home, I think I'd fire it up on the muffs, and add some carb cleaner or good fuel additive with carb cleaner in it.

Do you run off a built in tank or a portable fuel tank?. Here's why I ask. If its a built in tank or a portable, try disconnecting the fuel and pumping about a quart into a clear container. Let it settle and see if you might just have some water that got into the fuel. I had same thing you got going on years back with a 75 merc, and it turned out to be some water in the tank. When I accelerated, the tank seemed to pick it up and the motor would still run by real rough. As I came up to speed and the bow came down, it just started running better, I think cause it wasn't sucking any water then.

If you only have a little gas in the tank, either type, then some fuel carb cleaner or fuel additive may help. With just a little gas in the tank, more cleaner gets thru the carbs. It might just be a partially blocked primary or secondary circuit on the carb, and if your lucky just the cleaner may cure it.

If checking the fuel lines and filters for leakes or clogs doesn't work, the easy things first, it might be time to have a mech look at it and check the carbs for synch or possible rebuild.

But do the easy things first.