Just one more thing

[Sabin]

I have a 27 foot Sportcraft with a 7.4 liter in it. Over the past 6 years I have spent more time working on it then using it. This year I finally have it going, I just went down to run it for a while to burn some of the old gas (some of it is 4-5 years old) When I walked down there was smoke coming out of the exhaust...no big deal but there was also some smoke/steam coming out of the carb. When I shut the boat off I heard almost like a percolating sound coming out of the carb. Is that just the moisture burning out of the old gas in the tank. I have a brand new water separator in it.

 

[HT32BSX115]

Re: Just one more thing

I have a 27 foot Sportcraft with a 7.4 liter in it. Over the past 6 years I have spent more time working on it then using it. This year I finally have it going, I just went down to run it for a while to burn some of the old gas (some of it is 4-5 years old) When I walked down there was smoke coming out of the exhaust...no big deal but there was also some smoke/steam coming out of the carb. When I shut the boat off I heard almost like a percolating sound coming out of the carb. Is that just the moisture burning out of the old gas in the tank. I have a brand new water separator in it.

Howdy,


Welcome aboard.......

Hard to say. If you're running 4-5 year old gas in your boat, You can plan on having SERIOUS problems with the engine.

The 1-2 year old gas might be ok if mixed with fresh gas in maybe a 10:1 ratio. (newld) But I wouldn't use 4-5 year old gas for anything but Weedkiller.

You are making a huge mistake.


Regards,


Rick

 

[Sabin]

Re: Just one more thing

Yeah I kind of figured that. When I say some of the gas is that old I would guess its right around 40 gallons. its a 110 gallon tank so 70 gallons are a year or two old. I dont feel like pulling the boat out of the water to syphon the gas out just to put $400 dollars back in. I may just have to so I dont blow the motor.

 

[HT32BSX115]

Re: Just one more thing

You will not "blow the motor" just running it around at idle. But if you try to runit straight and you load up the engine ......I.E. full throttle holeshot and running up to plane etc, You run the risk of a detonation event that could break pistons and burn valves.

It it's really only 1-2 year old gas, then you could dilute it with fresh gasoline and probably be ok.

If you really only have about 40 gallons of 1-2 year old gas in it, I would push a small tube down into the tank, pump out 20 gallons or so and fill it up with fresh gas (assuming you're going to run the boat.....)

When I shut the boat off I heard almost like a percolating sound coming out of the carb. Is that just the moisture burning out of the old gas in the tank. I have a brand new water separator in it.

I doubt it. That sound could be the float leaking or (if the engine was really hot) the fuel boiling in the carb.......although the vapor pressure with really old gas is pretty low (which makes the boiling point a little higher)


You said it's a 7.4L engine. What manufacturer and drive?

 

[Sabin]

Re: Just one more thing

its pretty much just a chevy/mercruiser 454. My boat is a 77 and the engine is an early 70's with what we call a v drive. I have also heard them referred to as a velvet drive.

 

[HT32BSX115]

Re: Just one more thing

its pretty much just a chevy/mercruiser 454. My boat is a 77 and the engine is an early 70's with what we call a v drive. I have also heard them referred to as a velvet drive.

It's useful to know the engine serial number. Mercury uses serial numbers instead of actual year model to determine parts, etc.


You're in the wrong forum too. There is actually a Mercury/Mercruiser I/O-inboard forum wehre you'll find a lot more people haning out who are intimately familiar with the setup you have.

I'll ask one of the MODs to move it.

Cheers,


Rick