Fuel problem in carb

[Emma_4594]

FYI: The boat stalls at both idle and full throttle

Please bear with me my husband is the one troubleshooting but this is what I know. - my terminolgy will be off.

we have a 1996 ski centurion - 350 magnum mercruiser -
problem: with the old 4 barrel carb - we were getting shortage of fuel on one side. - we assumed it was the ethinol issue

we found dirt had the carb rebuilt last year and had new fuel pump last year

the problem again started this year. - cleaned fuel tank replaced fuel hose, filters etc.

we decided to go with new carb bought and edelbrock 1409 - now fuel just stopped and boat stalls.

We are now purchasing a new fuel pump - do you think we may on right track? or are we chasing our tails

 

[Gary H NC]

Re: Fuel problem in carb

Did he verify the fuel pump is not pumping?
When the tank was cleaned was the pick up screen removed and cleaned also? As well as the anti-siphon valve and make sure the vent line is open.

I assume that model has the electric fuel pump so you may have an electrical issue.

 

[HT32BSX115]

Re: Fuel problem in carb

Howdy,

Well you might not be "chasing your tails" but you're clearly replacing things that are not the problem! E10 is probably not the problem......(I guess you found that out)

If you have fuel "stoppage" you should start at the tank. .... and work your way to the carb.

There's usually a fuel screen inside the tank and a anti-siphon "valve" at the tank where the fuel line connects. If the screen or anti-siphon valve is plugged with debris you'll get fuel stoppage.

If the filter or any fittings/hoses are plugged or the fuel pump is defective , same thing. It's usually not the carb. (I assume you looked inside the carb and it was clean?)


Cheers,


Rick

 

[Gary H NC]

Re: Fuel problem in carb

I finally beat ya Rick...lol!

Where are our manners?

WELCOME to Iboats Emma!

 

[HT32BSX115]

Re: Fuel problem in carb

I finally beat ya Rick...lol!

Where are our manners?

WELCOME to Iboats Emma!

Yeah.......and I type REALLY SLOWWWWWW!

 

[Emma_4594]

Re: Fuel problem in carb

It is a mechanical pump - vent line was checked will double check Pickup screen in tank but not sure where antisiphon valve is? Thanks for help- any other ideas -

 

[Gary H NC]

Re: Fuel problem in carb

Yeah.......and I type REALLY SLOWWWWWW!

me too Rick...

Emma,
The anti-siphon valve is in the fitting that screws into the tank that the fuel line clamps to.
It has a ball type check valve in it.
When he unhooks the fuel line at the carb and cranks the engine over is it pumping anything?

 

[Gary H NC]

Re: Fuel problem in carb

Here are some pics of the valve...scroll down the page..
http://www.moellermarine.com/aftermarket/fuel_systems/valves/

 

[Emma_4594]

Re: Fuel problem in carb

Thanks for the pics -

When he unhooks the fuel line at the carb and cranks the engine over is it pumping anything?

If i understand this question I can say yes. When he installed the new carb the connections screws were not fitting right so the gas would leak. The boat will run for about 5 - 10 min before we start having the fuel inconsistency. (low speed and full throttle). If we let the engine stay off for about a minute or so it starts up for a while then again the problem.

 

[HT32BSX115]

Re: Fuel problem in carb

Emma, The anti-siphon valve won't look like a "valve" at all.

It looks more like a simple hose fitting or "barb".

Since the fuel pump must overcome the check ball in the A/S valve, if there is even a slight leak between the valve and the pump, it WILL suck air into the system and could be the source of your problem.

If you disconnect the fuel line at the carb and you crank the engine you should get a stream of fuel at the end of the hose (NO SMOKING btw!!!)

 

[Emma_4594]

Re: Fuel problem in carb

I will have him try this.

 

[HT32BSX115]

Re: Fuel problem in carb

It will be a LOT safer if you use a short piece of clear vinyl hose to connect to the line you disconnect from the carb and hang it over the side (have someone hold a container to catch the gasoline so it doesn't go on the ground)

You don't want liquid gasoline exposed in the engine compartment because possible sparks etc.....

Do it outside in the open and have a fire extinguisher handy!

 

[Emma_4594]

Re: Fuel problem in carb

It was the hose that was connected to the pick up screen was filled with stuff. So we blew that out. Then took the boat for a ride. It was like brand new EXCEPT kerplunk kerplunk sounded like we blew out a muffler. The whole boat was vibrating. We went under and there was nothing attached to prop or the prop was not loose. Which section should I enter now.

Thanks for your help with the fuel.

 

[Gary H NC]

Re: Fuel problem in carb

It still could be a fuel issue.Now that the line is clear the filters should be changed.The carb could have sucked in some crud.

Not sure about the loud noise unless it was a misfire in the cylinders..
Was the noise coming from the engine or did it sound like the drive making noise?

 

[HT32BSX115]

Re: Fuel problem in carb

Oh boy

Sounds like something happened to the Velvet drive or something.....

"Kerplunk Kerplunk" doesn't tell us much though!

 

[Emma_4594]

Re: Fuel problem in carb

velvit drive was about 1/2 quart low added some and ran better.

 

[HT32BSX115]

Re: Fuel problem in carb

Um....low oil in a V-drive would not make a noise nor would adding oil make it "run better".


Something else is going on there....

 

[Emma_4594]

Re: Fuel problem in carb

could an exhaust baffle cause the vibration? He put the fluid in and then the boat ran fine?? He said I was not in the boat at that time. But the best way I could explain it was it felt like in a car when you blow a hole out of your muffler, Loud noise and vibration, but we did hear a kerplunk kerplunk first.

 

[renny1]

Re: Fuel problem in carb

sorry i really need to jump in here and say thank you for making my day the KERPLUNK KERPLUNK has kept me laughing for ages now

 

[HT32BSX115]

Re: Fuel problem in carb

could an exhaust baffle cause the vibration? He put the fluid in and then the boat ran fine?? He said I was not in the boat at that time. But the best way I could explain it was it felt like in a car when you blow a hole out of your muffler, Loud noise and vibration, but we did hear a kerplunk kerplunk first.

That's a hard one without hearing it.

With the V-8 you probably have standard manifolds, risers and exhaust tubes ext.....There may be exhaust "flappers" in the exhaust system that *may* be loose and are rattling around in there ...

This is a case where it might be a good idea to post the Mercury serial number of your engine.
(everything unique to Mercury engines is serial number specific.....not necessarily year model.....)

Also, Centurion may have put some other sort of anti-reversion "flapper" in the exhaust system after the Mercury "stuff" that has come loose etc...

They would help prevent water from running back up into the risers after a rapid deceleration or if the engine was shut off whilst underway (don't do that intentionally btw)