is it possible to treat old fuel in the tank

[dlogvine]

The most recent tags on the 2008 Baja Islander I purchased are from 2016. The tank contained about 1/4 fuel. I added Enzime treatment and Stabil for fuel and filled the rest with the 91 high octane fuel. The engine is newly rebuilt and installed 1993 Mercruiser V8 305. Old fuel did not have this bad smell of rotten fuel, so I assumed there could have been some fuel stabilization treatment applied. I'll try to start the engine tomorrow, but at first the engine was cranking without an ignition.
I really would hate to evacuate the tank. Thank you

 

[achris]

Check spark.

Fuel does lose it's ability to resist knock (lower octane number) as it ages. But as you only had 1/4 of a tank, and you added 91, that should minimize any fuel problems. May be worth draining from the tank pick up to the engine as that will not have benefited from having 91 added to it.

Chris.......

 

[dingbat]

My biggest concern from sitting for 3 or more years would be moisture. Check and drain the fuel filter often

 

[achris]

My biggest concern from sitting for 3 or more years would be moisture. Check and drain the fuel filter often

If you're concern about water in the fuel, throw in a litre of meths... Problem solved.

 

[dingbat]

If you're concern about water in the fuel, throw in a litre of meths... Problem solved.

We already have 10% ethanol in our fuel.

Any (free) water in the tank is the result of phase separation. Adding more alcohol isn’t the answer. Physical removal via a filter/separator is the best solution.

 

[dingbat]

If you're concern about water in the fuel, throw in a litre of meths... Problem solved.

We already have 10% ethanol in our fuel.

Any (free) water in the tank is the result of phase separation. Adding more alcohol isn’t the best solution. Physical removal via a filter/separator is prefered