I have an 80s model 25 hp Johnson that's been mine for a little less than a year. The thing starts right up every time, and runs well...for a while. But then it just bogs completely down and when this happens, it "surges"...revving high then low then high then low... I've had the motor in the shop twice, the first time was before I ever ran it...just to have it gone thru, impeller replaced, etc...then the second time was after I recognized this issue, and they went thru the carb and replaced spark plugs etc. Still does it. It will run well for a few minutes, but then it does the above, and it seems as though it only does it if I'm at WOT. When it happens, I kill it, and start it right back up. Sometimes it's still doing it, sometimes it's not...and I can baby it in. But I want to be able to run it at WOT when going from dock to spot and vice versa. Any ideas? Suggestions? Snide remarks?