2001 Yamaha 15HP 4 stroke Running rough at Idle

[Mendnit]

Hi everyone,
I have a 2001 15HP 4 stroke. Model F15Z It is electric start (My Dad's). It starts OK with the choke pulled out, but even after 3-5 minutes of idle with the choke out, as I push it in, the motor start to increase RPMS, and then dies when the choke is all the way in. I cannot seem to keep it running at idle at all with the choke all the way in. I pulled the plugs and cleaned them, but have not yet replaced them. They were a little black, but not completly black and not gunked up at all. Any ideas?

Thank s in advance,

Tom M.

 

[cousinabe]

Re: 2001 Yamaha 15HP 4 stroke Running rough at Idle

sounds like your carbs have trash in them.
Does pumping the primer ball help anything?
when was the time the motor ran right?

 

[Whoopbass]

Re: 2001 Yamaha 15HP 4 stroke Running rough at Idle

My 6hp Suzuki 4 stroke was running rough after it sat for a few months.
I pulled the carb, disassembled it and soaked it overnight in some cleaner solvent. I sprayed it out with some carb cleaner then blew it out with compressed air and installed it.
Ran like new after that.

 

[Mendnit]

Re: 2001 Yamaha 15HP 4 stroke Running rough at Idle

Hi Guys, OK, I pulled the card and cleaned it, and took it out again yesterday. It ran smoother, but I still needed to run it with the choke slightly closed for it to run right. If I push the choke all the way in, it still stalls right out. ......but here is the story on this engine. It was purchased down in florida but I am now using it in West Michigan and I use it mostly in the early spring and late fall for fishing. It is somewhere around 30 to 50 degrees when I am using it. I feel like it is running too lean. There looks to be a brass cap over the mixture control, and if I can adjust the mixture, I think it will smooth it out. I just don't know how to get this brass cap cover off. Any ideas?

 

[cousinabe]

Re: 2001 Yamaha 15HP 4 stroke Running rough at Idle

read this post.
http://forums.iboats.com/showthread.php?t=204516

with a small drill, drill through the cap (barely) then screw a small self-tapping screw in and pull out. Proceed the way you would normally clean any carb by opening what you can and thoroughly spraying every orifice combined with compressed air. Before dissassembly turn your idle screw in and count how many turns. When reassembling, back the screw out an extra 1\4- 1\2 turn if there is an idle problem.

 

[kbear291]

Re: 2001 Yamaha 15HP 4 stroke Running rough at Idle

Just bought a 01' 15hp Yamaha, haven't used it yet but what you are saying definitely sounds like carb problems. I would like to get a service manual for mine which seems hard to find, this is how I came upon this thread. There is also a small spring type plunger with a rubber boot on the side of the carb that
I found to be leaking. You can test it by putting a flat head screwdriver on the top of it and pressing up and down. If it leaks it will spray gas, replace it if leaking.