Power drops after about 30 seconds at high rpm

[imported_Jay]

I am new to the world of boating so please excuse my rookie questions.
I have a Johnson 50hp Seahorse. I bought it used, stuck in the water and off we went. It was running good for about 1 hour and suddenly there was a drop in power while cruising at full speed (which is about 18 miles per hour on the gps). It will run fine at half throttle. I changed the plugs which were black and somewhat oily. The gap on the plugs was .27 so I left the new ones at .27.

I also cleaned the fuel filter screen (which was full of junk) and replaced the old gas tank with a new tank and gas mixed 50:1 as advised by seller. The last thing I did was spray carb cleaner in the carbs, let it sit for 15 minutes then ran at fast idle for 15 minutes.

After all that I still have power loss at full throttle. Did I possibly clog the crap out of something by running old gas in the first place? Did my attempt to clean the carb just push the gunk somewhere else down the line to clog.? :/

 

[tashasdaddy]

Re: Power drops after about 30 seconds at high rpm

jay take an induction timeing light with you. when it starts acting up hook up the light. and check for spark on each plug wire. sounds like you are dropping a cylinder. you didn't state what year or the model #, which would help as there are a lot of 50 hp's.

 

[Texasmark]

Re: Power drops after about 30 seconds at high rpm

If you check the spark and come up with nothing you may have done what you said in your fuel system.

Never good to run questionable fuel. The problems it can cause way outweigh the cost of replacing the fuel.

Mark