Conference vicki::boats

1233.0. "Power Loss - Fuel problems? " by WONDER::CASABONA () Mon Jul 24 1995 16:24

Hi All,

Any of you I/O or Inboard folks having trouble with engine surging - possibly
suspecting gas quality?

I have a Mercruiser 488 which seems to have a problem with losing power while
under load.  I can set the throttle to about 3500 RPM and the engine run at
this speed, then lose power, then come back to speed, and continue this process
for a while with varying frequency. This occurs at any reasonable speed.

The problem seems to come and go.  I can start out in the AM and have the
problem, after about 10 minutes of run time,  let it rest for an hour, use 
the boat again with no problem, then use it later with the same problem.

The problem feels like water in the gas.

I have had the tank pumped and there was water in it.  It was refilled and ran
for a couple of days with no problem.  Then the problem would start again.  I
don't think there was any way for water to enter the tank during this period
other than condensation, but this has never been a problem to date (13 years). 
I let the tank run down to about 5 gallons and filled up (22 gals).  Boat ran
OK for a day and then the problem started again.  I put in a couple of bottles
of dry gas ran it for a while to shake up the fuel, let it sit for a couple of
hours, and it seemed to run OK. - I then had to leave.

The brand of gas is Gulf.  The Marina claims it is the new "formulated" stuff.
A friend had trouble with his VAN after filling up from the same station.
After letting his tank run "dry" he filled up elsewhere and had no
problem.

My suspicion is that the marina/Gas Station may have a problem with water in
his gas, but his pride does not allow me to confirm this with him.  Another
possibility is the quality of the gas itself - is it possible that, if it is
the "formnulated stuff", that it breaks down?

I have heard rumors of others on the lake having similar difficulties with
other fuel sources.

My next step is to try another marina. 

During this period, we have also had a complete tune up, had the Carb
accelerator pump replaced, and am about to have the distributor replaced due to
excessive shaft play causing misfire at the real high end (the point gap
changes due to wobble).  but...  the power loss problem seems to be independent
of the above "repairs".

Anyone else having fuel difficulties?

regards,
Rick

    re: .1 
    
    I've been wondering about the issues that "RFG" pose. Doesn't "RFG"
    contain something like 10% alcohol - and isn't alcohol hydroscopic
    to begin with? (that's what "gas drier" is made from, right?).
    
    So if your dealer has a water problem to begin with, I would think he's 
    going to be "enhancing" the product (which because of the alcohol content 
    will be only too willing to transport that water from his tanks to yours)...
    
    But then, I could be wrong ;^)
    
    /dave

    Low down on the probility list of causes are.  A leak in the intake
    manafold, and overfilling the oil.  Both can cause intermittent loss of
    power.
    
    One other symptom of water in the gas is backfiring at high rpms. 
    Check the fuel filter/water seperator for water.  The paper element
    sometimes gets saturated with water and will be forced out at high fuel
    flows.
    
    KC
    

    We had an intermittent spark plug wire.  Vibration and Heat seemed to
    be the aggravators.  Finally went to hard failure mode - with engine
    working on three cylinders.  replacing the wire did the job...
    
    r.