3.0 seems low on power and dieseling at shut off

[emilime75]

Had no issues last season when it was put away. Winterized and added fuel stabilizer to a tank just below half full(about 12 gallons in a 26 gallon tank).

4 weeks ago it was de-winterized, fuel/water separator replaced and tank filled with non-ethanol gas. I don't recall if it was 89 or 91. Took the boat out twice and all was good, just like the year before. 3rd time out and we seem to be down on power and about 5mph below normal top speed, and when turning the engine off it diesels for a few seconds.

Quick search seems to indicate a low quality fuel issue, and additives helping if not clearing it up. I'm not so sure and am wondering if it is a carb issue.

Any thoughts?

 

[Scott Danforth]

dieseling will kill your motor. that last gasp as the motor stops is it running backwards sucking in water from the exhaust.

look at your fuel quality and your ignition timing.

if you have points, service them.

 

[Alumarine]

In the meantime, try letting it idle for a minute before shutting it down.

 

[emilime75]

dieseling will kill your motor. that last gasp as the motor stops is it running backwards sucking in water from the exhaust.

look at your fuel quality and your ignition timing.

if you have points, service them.

It's an '06, so no points. All ignition parts were replaced last season with less than 20 hours on them. Plugs, wires, distributor cap and rotor.

Aside from the hold down bracket bolt on the distributor coming loose, what could cause the timing to change?

How does one test the quality of the fuel?

 

[emilime75]

In the meantime, try letting it idle for a minute before shutting it down.

I did, made no difference...maybe it wasn't as long as I think it was and I should try letting it idle longer.

 

[emilime75]

I did do a bit more reading and I am becoming convinced that maybe it is a fuel quality/octane issue along with a hot motor, after all. I'll try some octane booster to see if that helps.

 

[Bondo]

I did do a bit more reading and I am becoming convinced that maybe it is a fuel quality/octane issue along with a hot motor, after all. I'll try some octane booster to see if that helps.

Ayuh,..... The 1st thing to do is inspect, 'n replace the fuel filter,....