Re: 50HP 1999 2-Stroke rough idle/stalls
hey, no need to guess...a little basic troubleshooting & you'll be back on the water in no time.
adding good gas to bad gas just leaves you with more bad gas. adding stabil to stale fuel = same result. Adding stabil to fresh gas is a good idea. I use seafoam myself.
motor sitting a long time = gummed up carbs. Myself, I'd rebuild 'em just on general principle.
But first, do a compression test. Compression should be about the same on both cylinders (difference less than 7 or 10% or so).
Next, spark test (not a "spark plug" test): get an inline spark tester (couple bucks at autozone), set the gap for 7/16", clip it to the engine block, attach the plug leads (one at a time) and look for a strong blue spark while cranking. If it can't jump a half-inch gap in the open air without a spark plug, it's not firing in the hole under heat & compression.
Take the opportunity to inspect the spark plugs. They should be champion QL16V (surface gap) in good condition. Replace 'em if they are in sorry condition otherwise reinstall.
If you have good compression and spark, rebuild the carbs. Order 2 carb kits from iboats, and a service manual (highly recommend the factory shop manual, try marineengine.com or kencook.com for that).
Follow the "carb cleaning and rebuilding" link from the "top secret file" at the top of this forum.
Note that your motor gets its lubricating oil from the gasoline, so any cylinder starved for fuel is not getting adequate lubrication.
Use only fresh 87 octane gasoline, and TCW3-certified oil in the oil tank.
Change the water pump impeller every 2 years and the gear oil annually.
In fact, if you don't know the age of the impeller, I highly recommend replacing it first chance you get.
welcome to iboats!
