fuel question

[glenn5]

Have a 88 searay with twin 350's. Had fuel problems twice this season so far. For example, tonight went to the fuel dock to get gas, enegines ran great, filled up with gas and engines started running rough shortly after I started them and would stall. If this was bad gas from the marina, would there not be enough good gas in the carbs to start the engines and get me off the dock before I started getting the bad gas to the engines?? Secondly, I did drain the filters and found no evidence of water or debris, I started the engines again and still not running properly, so I changed out the filters off the fuel tanks but they seemed to be OK, but engines appeared to run smoother but still not as good.

I had this problem earlier in the season, I drained the filters and engines ran perfect. I'm baffled?? Fuel looks OK, is there any other indication that you are getting "bad" or "stale" gas??

Thanks

 

[glenn5]

would adding an octane booster help???

 

[Vince_nj1]

I suspect Ethanol is your problem: Google "Ethanol older boats" and read about it.



Ethanol Fuel
Boaters are now faced with a new problem - ethanol fuel. For years, gasoline contained MTBE, an additive which controls the fuel's octane properties. The additive is being phased out, and now much of the nation's fuel supply is a blend of 10% ethanol and 90% gasoline, commonly referred to as E-10 fuel.

Ethanol presents several problems to boaters. The immediate impact of the formulation is a loss of horsepower and fuel economy. Early indications show drops of 3-5 % in of both categories. The loss of range sounds small, but adds up on boats that are often already stretched to the limit in terms of fuel needs. Additionally, ethanol is a very effective solvent, and has a tendency to dissolve old coatings of varnish and dirt in existing fuel systems. This can lead to plugged fuel filters, and other mechanical problems.

The added amounts of particles associated with ethanol fuel may warrant upgrading filter systems. Many engineers are now recommending that boats using ethanol fuel need to use 10 micron filters. Pre-E-10 systems will likely be using 28 micron filters. Manufacturers such as Yamaha have been quick to respond to ethanol fuel use by introducing replacement 10 micron filters.

The corrosive nature of ethanol can affect fuel lines and other components, causing them to crack and fail. Many older boats will require replacement of all fuel hoses and possibly other system components. Especially affected are boats equipped with fiberglass tanks. Many older vessels must have the fiberglass tanks replaced prior to using E-10 fuels, or face certain engine failures.

Water in E-10 fuel is another problem that boaters must deal with. The introduction of water on E-10 fuel can be disasterous. E-10 can hold up to four teaspoons of water in suspension per gallon. Once this saturation point is exceeded, the solution separates and the gas floats on top while the ethanol and water mix on the bottom. This event is called "phase separation". Ethanol fuel can absorb enough water to reach it's phase separation point in just over 3 months at 70% humidity.

While the phase separation slurry in itself can cause problems by clogging fuel systems, the more immediate problem is that the remaining gasoline has now lost it's original octane value which can cause poor running and in some cases engine damage. When phase separation occurs, the fuel should be drained and replaced.

Fuel storage and winterization has to be handled differently when using E-10 fuels. Manufacturers are warning that fuels need to be stabilized if un-used for as little as 2 weeks. Not all stabilizers are known to be E-10 compatible. Non-alcohol based fuel stabilizer additives are a must for ethanol fuel.

 

[Sundancer]

While bad gas or Ethanol could be an issue, I suspect it could just be junk in the tank blocking the pickup. I'd suggest emptying the tanks and taking a look to see if you have some stuff floating around in the bottom of the tank. A fill up will get it stirred up and it can block the pickup. Just a suggestion, especially if it happens right after a fill up.

 

[glenn5]

have talked to a few people in the marina, they all seem to have the same problem. In suspect a fuel problem, talked to a mechanic and ethanol is not an issue, but from what I read, it maybe. if it was just my boat in the marina, i would suspect a problem with my enigne. Putmethy hydrate in the gas, engines are running better.

Thanks