EVINRUDE 9.9 - Doesn't run great all the time - '76

My 9.9 has me scratching my head. Here's the problem.
So I drive across the lake, wide open, the motor runs great. I get to the other side, go to the bathroom, come back and it takes 20 pulls to start the motor. Then taking off, it acts like it is running on one cylinder sputtering but still moving the boat just not very fast.
It seems like it is flooding out. I have new plugs in it. And after letting it sit for a prolonged period of time without running, it starts and runs just fine.
Is this something as simple as an adjustment screw on the carb or maybe the seafoam in my gas or did I accidentally add too much oil?
Thoughts?
Suggestions?
What to try or look for?
Thanks,
Kyle

Could be a coil breaking down after it gets hot, then returning to normal operation after it cools off. Have you tested enough to determine which cylinder is failing when it's running bad? If so, switch the coils around and see if the problem follows the coil to the other cylinder.

I had a similar problem with my 50hp Johnson. Jim chapel has a great idea. Next time it starts acting funny you can pull one plug wire off at a time. If you pull one off and the motor doesn't die then that cylinder is dead. Also I've herd of the diaphragm in the fuel pumps will start to break down when they get hot and cause those kinda problems. I'm no expert but I know how you feel and it drives you nuts! It's definitely a fuel or fire problem if compression is good. Just do a process of elimination. Start with a compression test and you can pull your fuel line from the carb. and pull it. It should spit a bit of fuel out and do the thing where you pull the plug wire off too. Also check your fuel lines and the bulb as I've herd that the ethanol fuel is eating them up. I only run 100% gas in my boat now. I put 6 gallons of ethanol gas in it and that's when I started having trouble.

Dam auto correct on my phone. Jmichael not Jim chapel!

Jmichael. Just seen your boat in another forum. I have a 12ft Jon with a 9.8 mercury that looks just like yours. What size motor us that?

[url=https://www.tinboats.net/forum/viewtopic.php?p=353988#p353988 said:

jonboatboy » Yesterday, 23:50[/url]"]Jmichael. Just seen your boat in another forum. I have a 12ft Jon with a 9.8 mercury that looks just like yours. What size motor us that?

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The motor pictured in my build is a 1975 20hp Merc.

My only thought is, why do you go across the lake to use the bathroom?

Just a question here...are you still running your "winter blend" gasoline?
If you even think you are then ditch whatever fuel you have left and simply get some fresh fuel and try it.
What you are describing sounds like a classic "Heat Soak" scenario. Fuel additives may also increase the possibility of heat soak.
Not going to go into a long explanation of heat soak here. Look it up if interested. Carbureted outboards are definitely prone to it and most prone right after Winter while the fuel in the tank may still have some winter blend gasoline in it.
Do the simple things first....this is definitely one of them.
By the way... the magic time for this to occur seems to be around the 20-30 minute shut down time after a good run. A check for it is that once you do get it started when experiencing this...and get it up on plane you can shut it off and restart and plane off repeatedly without issue until the next period of 20-30 minutes of shut down time.

[url=https://www.tinboats.net/forum/viewtopic.php?p=354051#p354051 said:

Zum » Today, 12:48[/url]"]My only thought is, why do you go across the lake to use the bathroom?

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Science aside, I think Zum is on to something. Tell us that when you get to the other side of the lake you are not pissin' in the gas tank again.



Sorry

[url=https://www.tinboats.net/forum/viewtopic.php?p=354106#p354106 said:

rickybobbybend » 29 May 2014, 23:43[/url]"]

[url=https://www.tinboats.net/forum/viewtopic.php?p=354051#p354051 said:

Zum » Today, 12:48[/url]"]My only thought is, why do you go across the lake to use the bathroom?

Click to expand...

Science aside, I think Zum is on to something. Tell us that when you get to the other side of the lake you are not pissin' in the gas tank again.



Sorry

Click to expand...

Simply enough - I wasn't going to crap in a bucket.

I haven't had time to check the coils or heat soak. I'll be trying it out this weekend. Thanks for some good tips and things to look for. I have a new fuel pump diaphragm that I'm going to install before hand just because I ordered it a while ago and might as well replace.
Fuel is all new this spring, new oil, and a couple caps of seafoam. New gas tank and gas line fittings as well.

Fuel this Spring may still be Winter Blend. You can spend a Hell of a lot more money on parts that some non-technical folks will tell you to buy when it may just be a fuel issue.
Use it in something else and replace with fresh fuel

I'm about 95% sure that it isn't winter blend and it is 91 octane.
Last night when I was working in the garage i decided to check the air/fuel idle knob that goes to the front housing which allows you to be lean or rich. I found that it was about 3-4 turns out from the recommended 1.5 starting point.
Does anyone know if turning that screw out increase fuel or air?

screwing the needle out will increase fuel.

That far out might be increasing both. :LOL2:

you might want to read through some of this if you haven't already...

https://www.leeroysramblings.com/Outboard Motor Related/OMC outboard related articles.html

I've read all of leeroys ramblings. I'm hoping the idle screw helps

Just run 89 octane fuel in it. No need to run high test at all.

So I ran it today and found when the problem started I was able to pull the top plug wire and it still ran the same. When i go out tomorrow I'll swap wires and and test to see if it's a coil problem

So when I switch around the plug wires then it switches which cylinder dies. Thus I have something wrong with the points/condensers/coils. Which is the best to start? Per my understanding in Leeroys ramblings, this is probably a condenser problem?

Are you pulling the plug wires from the coils and swapping them?

You can check the condensers with a meter.
Remove condenser, set meter to resistance (ohms) and hold one lead to the wire connection and the other to the condenser body for a bit (this will give it some charge). Then quickly switch the meter to voltage measurement. You should see a voltage reading that with a short amount of time degrades to zero (discharge). A condenser is simply a capacitor.

I'll send you a troubleshooting guide that will give info on testing the ignition "stuff."