I own a 90 hp Johnson 2005 on a 20ft pontoon. The motor was running great and 2 weeks ago it would during idle, just stop. and I would turn the key and it would start right back up. Then it would seem like it would only go half speed and surge with quick jumps, then half speed. I cleaned the fuel filter and no help. Filled the gas tank with 93 octane last week and after it ran GREAT ! 1 week later I (it surged and ran half speed), idled to a friends house,let it sit for about an hour, idled 10 minutes back up the canal and now it runs great again. Do I have an electrical problem, or fuel? Also, it has always been hard to start, Crank for 15 - 20 seconds, and doesn't like to idle until it warms up. Any help or ideas would be greatly appreciated. And I did change the spark plugs a month ago, before this all started but it has been getting worse. Thanks in advance to all.
FYI to all.
I was somewhat shocked that nobody replied or had an idea what was wrong so I took it to the dealer. The solution was a twofold. a new ignition pack fixed the high speed issue. And one of the gaskets on one of the 4 carbs had taken a set allowing a slight anount of air to disrupt the vaccum and affect the idle. Runs and idles like a CHAMP! I wanted to atleast reply so others may learn.
If you run into these types of problems its simple to troubleshoot with a spark GAP tester, spark needs to jump almost 1/2 inch gap, $12 from any decent auto part store, get one for future use.
You're fortunate to find a mechanic at this time of yr who isn't backlogged.
All swell that end swell.