CONTINUOUSWAVE

I have 2007 Mercury 60-HP Big Foot ELPT outboard with very little hours. I purchased the engine new and never had a problem until July 2022.

I left a tank of 87-octane fuel on the boat in September 2021, adding the fuel stabilizer in the tank over the winter in Ontario, Canada. Once running on the lake this year, July 2022, I have noted the rough idle and the engine would die after putting into gear and going forward or backward. After multiple attempts to start/choke/start/choke, the engine eventually gets going, after about five minutes it actually is running well. The rough idle and engine dying when put in gear happens again after the engine shuts off.

I have changed the oil, spark plugs, and the fuel filter. The problem persists.

Q1: what is the remedy?

Thanks in advance.

Do not use the existing stabilized fuel.

Drain the fuel from the fuel filter, high pressure rail and the VST.

Fill the tank with newly purchased fuel and run the engine. After an hour of use, report back the results.

Make sure the empty fuel tank is clean. Get new ethanol free-fuel and add a large dose of SeaFoam or Yamaha RING FREE to clean the small passages in the fuel system. After warmup, I’d run it at high engine speeds on the water to get the fuel system and engine system hot to aid in cleaning out old gasoline and the varnish likely in the fuel system. Good idea to do this once annually. Ethanol fuel with go bad very quickly when left sitting.

If you use a portable fuel tank consider removing the fuel line from the tank and sinking it in fresh fuel from another source. Then test run the engine for a few minutes on the muffs for long enough to have cleared all the old fuel from the hose, filters, fuel rail, etc. If the engine continue to run badly you will know the problem was not caused by bad fuel. If the engine symptoms continue consider consulting with a certified Mercury Marine technician. If your boat has an in-deck tank it is more difficult to connect another source, but may be worth the effort.

Regardless, I recommend recycling the old fuel, perhaps into a vehicle.

I made the mistake of leaving properly treated fuel in a Mercury fuel injected four-stroke engine over the Winter and had to pay a shop to clean out the system. I now test run the engine on the muffs once a month or so. That seems to work, so far.