yamaha 4 stroke 9.9 bogging

[qwest]

Hi,
I have 1998 yamaha 9.9 four stroke (mshw) that bogs when given throttle. It will intermittently spurt up and run as it should but only for a few seconds then goes back down to bogging speed. seems to idle fine. I know that gas is at least getting to the carburetor, I also removed and cleaned thoroughly but still have same issue.

Could this be a spark issue?

 

[w2much]

Yes it could

 

[99yam40]

loosing spark or too much or not enough fuel in a cylinder
timing light should indicate if spark is hitting and if it is hitting at the correct time