98 Yamaha 115 2 cyc runs great then it doesn't?

98 Huricaine 201. 115 yamaha runs great, starts easy and then sometimes it will bog to the point you have to put it in neutral for 30 seconds before you can take off. It never stalls to where you have to restart. Sometimes after it has bogged down and you go to take off it runs rough (shutters) and won't go at all. Give it just a little gas and it will run ok and you can gradually get up to speed before it crumps out again. Sometimes when it is shuttering and running really bad if you give it just a little gas it will come out of it at the snap of your finger and run great again. Changed the water fuel separator, fuel lines, bulb a few months ago and it was fine. Just changed the fuel pump, bulb pumps up fine and stays solid. When this acts up pumping the bulb does not change anything. I will put volt meter on battery tomorrow cause it says 16-17. No rotten egg smell from the batt. (my guess is the gauge is off and unrelated) Boat was run all season every month since mid last year, just put 89 non ethonol in it and ran it several hours no change. Plugs looked good last year and clear filter on engine and filter on the bulb is flowing good. I am a fair car mechanic but boats are a different animal. I am thinking it may be electrical? Any thoughts any one? Thanks

Re: 98 Yamaha 115 2 cyc runs great then it doesn't?

I also have a Yamaha 115 two stroke, and have gone thru the same problems every few years. Mine's a 1985 model--and still runs great.

I would go ahead and purchase 4 plugs--and 4 extras to keep in the glove box. Changing plugs just takes 5 minutes.

Second thing is to pull the spark arrestor, and run the engine for a few minutes. Stop the engine and look down the carb. throats. Is there any drip, drip, drip--indicating stuck or gummed up needle valves.

I would be quick to get some carb. cleaner, and clean the carbs. Be careful with your gaskets on disassembly, and no kit will be needed. Just note how many turns any adjusting screw takes to tighten down--and set them back at the same place after you clean'em. They're pretty simple carbs to clean.

If the problem's not been solved, another plan of action will be needed. 2 strokes are not very complicated animals.