Yamaha 50HP running rough

[pmarker58]

I have a 2001 Yamaha F50 4 Stroke Outboard motor. All of sudden it is running rough like the choke is on but I do not know how the choke works since I have no switch to choke the engine. I checked compression and it is good in all cylinders. I checked the spark and each one is good. I put new gas and some seafoam in and ran it around the lake and it still running rough. Any suggestions on what I should look at.

[TownsendsFJR1300]

You have "prime start" (automatic) choke;

2001 F50TLRZ Yamaha Outboard CARBURETOR Diagram and Parts

Has the engine sat for any length of time and if so, did it have a fuel stabilizer in it?

Any and all history would help too...

[pmarker58]

2001 F50 running rough

When I put my pontoon boat away last year. I filled the 30 gallon tank and I also put a can of SeaFoam in which is a stabilizer. I used the boat all summer and when the tank got down to a 1/4 tank is when it started to run rough this summer. I then put in 15 gallons of new gas in plus a can of Seafoam to see if it would clean out the carburetors. I ran it around the lake a couple of times to see if it would clean it out but with no luck. I also drained the gas on all 4 carburetors using the small brass screw on the side. Ran it again and it is still rough. My thought is the carburetors need to be cleaned but I wanted to make sure I ruled everything else out since that looks like a big job. Also does this engine have a choke and how does it work since I have no switch to turn it on and off.

[TownsendsFJR1300]

Click on the link I provided, part #31 is the prime start,(CHOKE) it IS AUTOMATIC.

It does sound like a carb(S) may be clogged.


Yamaha's "Ring Free";

https://www.shopyamaha.com/product/d...?b=Search&d=34

works WAY better than Seafoam. You can run it 2-3 x' the recommended amount for badly clogged carbs. May work for you at this point, may not depending on how bad its clogged.

A sure way to make sure the carbs are NOT clogged would obviously pull them and VISUALLY check the jets. Simply shooting air into a jet doesn't cut it.

For long term storage, simply drain the carbs at the drain screws. If not, just a little bit of fuel remains and WILL varnish up..