Mercruiser 5.0 carburetion problem ...should I drain my fuel tank?

[dmillerss]

Last season my 2003 boat started running poorly at high RPM’s …. Bogging during fast acceleration, acting as if it was being throttled down while running, going from fast to low RPM’s on its own, etc. I was unable to throttle past 2,000 RPM’s, but boat started and idled without a problem. Replaced the fuel/water filter and that fixed the problem for the remainder of the season.

This year I experienced the exact problems detailed above the first time out, including unable to run much past 2,000 RPM’s. I again replaced the fuel/water filter … that certainly had a positive effect: able to reach high RPM’s. However, the problems with bogging during fast acceleration, acting as if it was being throttled down while running, going from fast to low RPM’s on its own, etc. still exist, but to a lesser extent. I'm at a loss as to what do now, and am wondering if I should have my fuel tank drained?

Thanks in advance for any advice .... D Miller

 

[Bondo]

Ayuh,...... Any crap in the fuel tank, is on the bottom,.....
No need to drain the entire thing, just suck the crap off the bottom,.....

I'm guessin' some of this stuff, made it to the carb, 'n/ or the fuel pump, causin' yer current problems,.....

 

[dmillerss]

Thank you for the feedback. Sounds like you don't think it's water -- but changing the fuel water separator did result in significant improvement. Worthwhile to dump out the separator and try some dry gas?

 

[Bt Doctur]

Why not dump the contents in a clear container and report your findings

 

[Eric 3.7LX Alpha 1]

Here's a pic I took of old left over gas from previous season in my boat's tank, and new fresh gas on the right. It's worth checking what yours looks like...

 

[mowinkid37]

also, if there is a small filter on the inlet line at the carb, this may be filled with gunk. that was my problem when it wouldnt get up past idle.

 

[dmillerss]

Thanks for the feedback. I changed the fuel/water separator and added dry gas .... ran it at about 4,000 RMP/35MPH for close to an hour with no issues. I'm posting a pic of what came out of the filter next to fresh gas. I'm down to just under a quarter tank; wondering if I should go ahead and drain it.

 

[dingbat]

Thanks for the feedback. I changed the fuel/water separator and added dry gas .... ran it at about 4,000 RMP/35MPH for close to an hour with no issues. I'm posting a pic of what came out of the filter next to fresh gas. I'm down to just under a quarter tank; wondering if I should go ahead and drain it.View attachment 343206

Dry gas is just more alcohol.
First off, do you have a good coalescing fuel filter installed? Those spin on “oil cans” are next to useless for actually “filtering” anything out of your fuel.

If you where to let the jar of fuel settle, you would end up with a pin head of water on the bottom of the jar of that. Put it through a good filter and burn it….

Mine looks like that every Spring. Change the fuel filter, top off the tank with E10 and go boating.

Had water twice. Filters completely full of “phase separation” choked out the motor. Took it home and pumped a quart or so of water off the bottom of the tank both times. Long story…..vented fuel caps installed in recesses. They make pretty good water vents too.