89 cobra 3 ltr miss.

[shimano]

My boat kinda had me puzzled.2nd year it has done this.first time out boat starts right up ran fine for the first hour( really good actually).then started to miss again.full tune up.new cap and rotor.new fuel filters.I even drained the gas tank and put fresh gas.when I was draining the gas tank(had to suck it out with a vacuum pump.it would not siphon)I saw air bubbles in the line.I have a large belly tank in the boat.could it be sucking air causing the miss?will the air get eliminated at the mech fuel pump? Anything else I should check.

 

[jerryjerry05]

Check the vent line.
Bugs get in and make nests and cut off the air.
Also if the coil is failing it will do the same thing.
You change the filter in the carb?
Not absolutely positive but I think there might be filter in the fuel pump????

 

[shimano]

I will definitely check those 2 filters.the vent.I think I'll put a clear line from fuel\water separator to fuel pump too see if it is sucking air.funny it ran very good for the first hour.will a automotive coil be OK?

 

[vinnie1234]

If your boat has a carb on top, the fuel that goes into the motor comes from the float bowl. The fuel from the pump dumps into the bowl and there is always air on top. Any air in the line would bleed itself out here. Try putting some gas line de-icer in your tank. you could be dealing with water. Fuels that use ethanol are notorious for pulling condensation out of the air and dumping it at the bottom of your tank. Since the fuel pickup is at the bottom at the back, often under acceleration or with the bow up you will suck in water. To be sure, you could always take off the top of the carb and look for water in the float bowl. It will always sit on the bottom as it is heavier than gas. If this is the case, you can always use your oil change oil extractor and stick the tube into the lowest corner of the tank and suck the water out. I always put a bottle of de-icer into every tank.

 

[shimano]

That is definitely what I thought. That's why I drained my tank this year but only siclrd out what I could through the gas line. I do have a fuel water separator that I added. And have added methyl hydrate before.glad to heat about the air getting eliminated at the pump.. .

 

[jerryjerry05]

Using any kind of vacuum to drain gas is dangerous.
It builds up static electricity and BOOM!
There is a anti-siphon valve at the tank.
It could be corroded and not opening.
The a/s valve will stop it from siphoning.
Ethanol can delaminate the inside of the gas line and stop the flow too.

 

[shimano]

When I was sucking out the old gas you could hear a rattling noise.sounded like in the tank.as the vacuum sibsidid.so did the rattling noise.could that be the anti siphon valve?I do try to run premium in the boat.a lot of places don't run ethanol in the hi test.it definitely sounds like water. I'm going to hook up a boat tank to it and see if it changes.I also have a new coil to throw on.