Help with Mercury 75Hp 2 stroke bogging down / surging

[ponyboy1995]

Hello all, I have a 75hp mercury 2 stroke outboard. It has been running great. Last weekend I took it out & it started bogging down. 1/2 to 3/4 throttle it would bog down then Rev back to where it is supposed to rev then back down & up until I pulled throttle back. At full throttle it seems to run ok. Then at idle it started sounding like it had a caugh or something like that. I tried to attach the videos but it says the file is too large. I have added the link to the videos below which you can hear the engine bogging down then reving backup it almost sounds like I am playing with the throttle but I am not. the 2nd video will show you the coughing or sneezing sound that the engine is making it idle. I already replaced the fuel line & primer bulb. The fuel filter looks clean & was replaced earlier this summer from regular maintenance. Any help would be appreciated. Thank you in advance!

 

[racerone]

Have to start somewhere and this is what I would do---Check for water in fuel tank.-----Check gear oil.-----Use timing light to see if you can pinpoint ignition issues on one of the leads.