Old Gas Question

[estame6]

Having a problem with my 1988 30 foot sea ray weekender with two 5.7L MIE 350 Mercruiser's. Last year I was unable to get much more than 2500 to 2800 rpm from both engines. I have checked the basic's but due to the engines being independent of each other I felt that the next step was to suspect the gas.

I have 3 gas filters, one at the gas tank, one mounted at the engine (water separator) and one in the carb. I changed all three with no residue found in any. I need some ideas but first I feel I need to I proof the gas. How can I check for old gas, the last couple of years I had some health issues and tended to only to top up the gas tanks and haven't use the boat for any long runs for many years.

Any suggestions please.....

 

[GA_Boater]

Moved this out of the Merc outboard section.

2 things to check;

• Open the tank fill and sniff. Does it smell like gas or old paint or varnish?
• Use a portable tank with fresh fuel and make a temporary connection to see if it is old gas in the main tank causing the running issue.

 

[fhhuber]

Old gas smells bad.
You can't miss it. It does not smell like fresh gasoline.
If it smells OK it will run OK unless there is water in it. Your water separator should show that problem.

I just ran 45 min yesterday on gas that's been in my secondary tank for about 6 months. I don't like letting the gas get that old, but it smells fine and ran fine. I'll be running the old gas on out till the tank is dry. (primary tank has 5 gal of fresh and that is enough for getting back when the other tank is now down to about 3 gal left)
Then the boat will have all fresh gas.

 

[Bondo]

Ayuh,.... I too, start with the Sniff Test,.... Bad gas, Stinks,.....

For diagnosis purposes, run the motors off remote tanks, like a pair of outboard 6 gal tanks, hooked right to the fuel filter at the fuel pump,.....

Large volumes of gas keeps much better longer than small amounts,.....
20 gallons keeps better than 2cc.s,....

 

[estame6]

Thanks, we are talking about 120 gallons and sniff test shows nothing out of the ordinary.
So my next question is can this corn additive now added to gas do damage to the o'rings in an old carb.
Again something that could effect both independent engines.
Looking forward to comments. Thanks.....

 

[maicoman]

Highly doubtful that the gas is causing your problems.One way to rejuvenate your gas is to add the Archoil product made to do same.Go to the Archoil website and read about their products quite remarkable stuff.I have used the gas additive for years in boats motorcycles genarators etc and have 100 percent success,The gas in my generators are over 4 years old and I start every fall to test and starts first shot each time,

 

[maicoman]

I think you should be looking at the ignition sections of your motors.If the carbs have been compromised by gas they will not behave well at all let alone just have lowered redline.Rotor Caps ,spark wires and plugs seems like a better start point.Good luck

 

[HT32BSX115]

Having a problem with my 1988 30 foot sea ray weekender with two 5.7L MIE 350 Mercruiser's. Last year I was unable to get much more than 2500 to 2800 rpm from both engines.

Howdy,

I use a mix (1/4 tank or less) of 1 year old (E10) fuel and fresh fuel every year. It never causes any problems at all.....And I have never used STABIL or any other snake oil in the fuel.......

You might have a look at the following thread (#15). You have already checked a few of the items but maybe not all.



http://forums.iboats.com/forum/engi...77-must-have-technical-information-for-diyers


Regards,


RIck

 

[jimmbo]

When you said you were only getting 2500 - 2800 from the engines. Was that with both running? Did you try to plane the boat using each engine separately, to see which one is the weak one. The weak engine will hold the stronger one back, and they will be running at the same, or very close to same rpm