200 Yamaha 4 stroke miss

[rinkrat66]

Help needed!!

I have a 2006 yamaha 200 4 stroke with about 30 hours that is not getting to full RPM's. Last year I was getting around 5800, this year 5300 RPM's. I pulled the plugs and found the #1 dark while the other 5 looked excellent. I installed 6 new plugs and ran the boat for about 1 hour. Pulled the plugs and found the #1 plug almost black and again the other 5 looked like new. I did get a faint gas odor towards the end of the 1 hour test run.

It seems to run OK. It doesn't idle as smooth as last year.

Any ideas where I should start??

[cast_and_blast]

Injector for #1 plug that is discolored. I believe there are directions on this site (search the forum) for removing and cleaning the injector.

Scott

[clarkend]

Sounds pretty familiar to my problem....see my post on my F150 issues below.

Let me know if I can help you out.

Clarkie

[MarkG]

Usually a darkend plug is due to that cylinder running rich,or not firing properly causing the plug to foul. I would think that typically, a clogged or failing injector would cause it to run lean and look white,not dark.

You can try cleaning or replacing the injector but also consider it could be a weak ignition coil,bad wire or possibly a problem with the fuel pressure regulator.

May also want to run a compression check on all cylinders and see how the one giving you problems compare with the rest.

[rinkrat66]

Mark,

I was thinking the same thing. I was thinking that it would have to be stuck open or partially open - if that is possible.

It is three weeks to get the thing into the local Yamaha guru so last night I cleaned the injector and installed a new plug. I took the boat out this morning and it is running great. It got up to 5800 RPM's instead of 5300 RPM's and sounded good.

Thanks for the replies fellas.

Good luck on the water!!

Bob.