I have an older (Late 80's) 15 horse Evinrude I am having recent problems with. When I used it for spring beaver trapping it ran perfectly but I had it sitting on my boat lift until yesterday since then without it ever being started. (shame on me)
It started first pull like usual but when I accelerated it went real fast for about 50 feet and slowed down to about half throttle. Squeezing the bulb did nothing to change anything but when I pulled the choke about half way out, it ran full speed like always. I thought my carb got gummed up by sitting so long so I put Sea Foam plus some Stabil in and added fresh fuel and let it run on idle for about an hour and took it for numerous spins also. It might have improved a little but still needs the choke partly pulled to run at full speed. I had put a brand new fuel pump in rt this spring and it has run like a top up until now.
What do you guys think my next step should be?

Sounds like carb needs cleaned. A piece of dirt in needle. Running Seafoam after the fact doesn’t always help.

Unscrew the drain plug under the carb. Usually a phillips or a straight slot (stupid idea). Put a shop towel under it and let it flow for 10 seconds or so. If you let it drain into a clear water bottle, you may see the water sitting in droplets under the water on the bottom of the water bottle. Gas on top, water on bottom. Condensation happens all year. You can add some HEET, or the new blue colored fuel stabilizer, but I forget the name of that one. I just started using it.

When you hit the gas, it sucks in the water, giving you a half throttle speed feel. Drain it, add a stabilizer to the tank, after checking the tank for water on laying on the bottom of the gas can. Your carb cannot gum up that fast. Sea Foam won't stop the condensation throughout the year. This should take care of the problem with what you described above. The choke issue is a dead give away for your problem as well. The minimum you should do is just drain the carb. That will probably do it. Sound like you already have fresh clean gas.

I have had pretty good luck introducing Sea Foam into it, running it for a while like you did and then let it sit for a day or two. Often times it will run like a champ then. Good luck!

You have water in the fuel system more that likely. It may just be in the carburetor bowl.
I would drain the gas tank and look to see if there is water in the bottom of the tank. It will bead up so you can see it.
Once I drain the tank, I take an old cotton t-shirt and stuff it in the tank to mop up what won't drain out.
As far as the carburetor bowl is concerned, I always remove the carburetor and take the bowl off to make sure the bottom of it isn't slimed up with residue.
Once I fill up with new fuel, and before I connect the hose to the carburetor, I use the squeeze ball to purge the old fuel out of the entire fuel line to prevent having to start all over.
There are other easier ways that might solve the problem, but I want the piece of mind that everything fuel related is covered before I get 2 miles from the boat ramp.

Seafoam is a stabilizer. You don't need to add sta-bil too. I wouldn't keep dumping any more additives. Drain the bowl and look for water like mentioned first.

Thanks, guys, Will do. I am still able to use it on the beaver job that is nearby. I did not mention that the gas tank was only about 1/4 full when I added the fresh fuel before I even ran the motor for the first time since spring. I am sure there is water in the tank from condensation. I will siphon out the gas into a bucket and then later, resiphon off the top gas back into the tank leaving the water layer remaining in the bottom in the bucket first and try it before messing with the carb or maybe just do both. I have done this with the gas tanks before and had good luck by doing it.

I also think it sounds like your not getting full flow on your fuel , so running partially choked helps draw a greater fuel air mix

when I am done running the boat for the day I pop the fuel line off my motor and run it dry because it might be weeks and weeks turn into the end of season too many times

it is easier do deal with what is in the tank and line draining it and if need be dumping it

I could see where a big jug or barrel with one of those valves on the bottom of air plane wings could be really handy put the questionable gas in , let it settle over night then drain the water off the bottom.

but for a few gallons just dumping it rather than having it wreck some other equipment.

I think still something stuck in a jet , maybe it works lose maybe a cleaning

Did you remember to unscrew the tank vent ?

This type of tank has no vent screw.

On 2 strokes, change the plugs every year.

I would do this,..it ran for an hour or so ?,. I would keep with that, should come out of it.

We're you running non oxy? Gas is junk these days and could have broke down in that time.

Over treating with seafoam can cause rough running as well.

If your gas is ethanol free the water will be on the bottom. You can tilt your can so the water ends up in a corner then just siphon the water out of that corner. Don’t forget to pump fresh gas through your gas line into a jar or can so you can inspect it as well.

A lot of times people clean carb, put fresh gas in tank but forget to empty the gas line. The first few pumps fills the carb with bad gas from the line. I have also found gas in gas lines goes bad faster than the tank gas. That may have been part of your problem too.

I have the same motor. It acted similar when the inside of the fuel line was collapsing. It looked fine on the outside but the liner was separated and closing up. I'd try a new fuel line from the tank, before I tore into the motor. Its a pretty common issue.

I have a 94 15hp Evinrude that ran just like you describe couple years back. The boat had set on trailer outside and uncovered. It has the metal 6 gallon tank which sat in back in the open.
When my motor was acting up after sitting for 3-4 months. I was really surprised at the amount of water in my gas tank. Literally was easily a quart. I think some of it was actually from rain forced in threw the vent hole in metal cap. That was couple years back when it was really rainy summer. Dumped the tank let it dry, refilled it ran some gas threw the line. Hook line up to motor. Took the drain plug out of carb. Ran some gas threw was good to go.
I've actually set my steel tank aside now and use a plastic tank. It has the vent cap you can close. Then the tank might swell or collapse some as heats cools. But it doesn't breath in humidity to condense in the tank. I also have my boat in the garage now that helps too.
As also mentioned above new plugs are cheap easy to just do regularly. Two strokes can be fussy sometimes with plugs especially the older motors.

Mac

"Never Forget Which Way Is Up!"

I would do the same ,eliminate the cheaper possibilities first , even pulling the carb if necessary .
After, run premium non oxy, have not had a problem for at least 20 years running high grade.

my log splitter is awful for collecting water

fairly regular I am pulling the 10mm plug out of the carb and letting it drain , one march I was having a problem get it to run right pulled the tank and there was a softball ball size chunk of ice in the tank , a bad tank design.

it can't be more than 2 gallons and I figure it was a good quart of water it had also plugged the screen in the bottom of the tank.

I’ve had that happen as well Jayme. I went to making my own hoses with auto gas line. Problem solved. That liner in marine gas line is supposed to keep ethanol fumes from leaking or something crazy like that.

Since it runs on choke., my guess is main jet restricted.