1991 Evinrude 150 doesn't run well, once warmed up

I just bought a boat with this motor. I mixed my first gas tank 100:1 just to make sure the VRO was pulling enough oil so for a while I was running it a little oil rich, but that gas should be all out and I should be running straight gas (and a little sea foam) right now.
When I first start the boat, it starts right up, idles smooth, goes into gear great, takes off perfect, but after running it for a mile or so, it will kill when I decelerate to a stop. After that it wont start with out some throttle and then once it's running it will often kill when I go to put it in gear and when I do get it running, it boggs way down when I try to give it some power. Eventually if you really, really ease it in, the RPM's will gradually go up, almost like it was flooded out.
When I pulled it out of the water, I tilted the motor up and some gas poured out of the motor housing. I pulled all of the plugs (didn't check for spark as a storm was moving in) and all 3 plugs on the left were wet and black and all 3 on the right were dry and clean.
I am a little intimidated to work on this motor by myself, but is there anything off the top of anyone ones head I should look for, before letting a professional charge me to take a look at it?

Re: 1991 Evinrude 150 doesn't run well, once warmed up

My 1986 Evinrude 150 hp just started doing the EXACT same thing as yours!!!! You described my motor exactly. Very interested in anyones input.

Re: 1991 Evinrude 150 doesn't run well, once warmed up

Well, the good news is there's only 3 things required to run; compression, spark, fuel. Any new-to-you motors needs to have a compression and spark test so you know where you stand, especially if you plan to have someone you're not familiar with, work on it. Just helps keep the cost down if you can go in and say, "Ok, I've check compression and it's 115 all the way across. Checked my spark and it's strong on all cylinders." That saves the mechanic from needing to consider it.

Have you checked your fuel system; i.e. lines, bulb, filters? How old are your fuel lines? When was the last carb rebuild/cleaning? Not saying it's simply fuel related, but combined with the above two tests, it would really help you to narrow down where the problem lies. Happen to have a service manual? If not, let me be the 1st to recommend getting one because lots of the troubleshooting tips are right there. I never considered myself "mechanically inclined" until I got my first service manual for my first outboard (197ish-100 Johnson) and realized that I actually could do a lot of what's needed.

Re: 1991 Evinrude 150 doesn't run well, once warmed up

Randy, mine ended up being an air leak in the fuel system. My electronic primer was cracked, sucking air, and leaking gas. Sorry this took so long to get back to you, but I have been out of town putting fish slime on a buddy's boat.