3.0 Mercruiser carburetor???

[Fishfearme1174]

Are these things really that sensitive to
moisture? Mine wouldn't start easy nor operate correctly at low rpms after finally getting started.
Drained gas tank and had carb cleaned rebuilt. Fresh gas in tank. Ran great for about a month and started pretty easily. The boat is located in south Florida on the water and last 5-6 days have been nothing but heavy downpour from hurricane hermine.

Boat now is acting exactly how it did before.

What is causing this and how do I prevent it? If I had my way I'd have the engine replaced with a fuel injection but I do t have that luxury.

What gives?

 

[Bt Doctur]

wet/damp ignition components that fuel injection wont cure

 

[Fishfearme1174]

Such as? Rotor? Distributor cap?

 

[stonyloam]

Start it at night and with a spray bottle mist a little water on the distributor and plug wires and look for sparks dancing around the wires.

 

[Rick Stephens]

I had a 3.0. That was pretty tired after 25 years. Compression wasn't too bad, but a vacuum gauge would show such an oscillation when under 1200 rpm that it made the engine much more sensitive to slightest changes in fuel, plugs, altitude etc. you might run a few tests to be certain the valves and compression are still up to standards.

 

[Fishfearme1174]

wet/damp ignition components that fuel injection wont cure

Totally unconvinced. Not too compelling man.

 

[Bondo]

Ayuh,..... When ya went through the fuel system, did ya find water, 'n crud,..??

A canister type water sep/ fuel filter should stop most or all of the water, 'n crud from gettin' to the carb,....

If yer still gettin' water in the gas, ya probably oughta go through, 'n clean everything again, 'n figure out just where the water is comin' from,....

If yer gettin' water in the fuel, BD is right, Efi won't fix it,...
It just costs a 'ell of alot more to fix it,....

If it Ain't water in the fuel, 'n it starts hard when it's rainin', it's probably an ignition problem,....

 

[Fishfearme1174]

Ok. Here's exactly what happened. Had carb cleaned. Had about 20 gals of fuel in the tank that has had a mixture of new and old gas over the last year but never completely drained. So after the carb was cleaned and everything was running good again I decided to burn all the gas out of the tank. I know I should ha e before the cleaning but I didn't. So after the tank was run empty I emptied the fuel water separator and more than half of it was water with some rust and a little silty crud. Motor was still running ok at this point. I then refilled with fresh gas and after a few small trips out it started acting up again. Does the carb need cleaning again?? When I empty the separator now it is beautiful %100 gas but did some of the crap actually make it past the separator and fuel pump filter and dirty up the carbs again?

 

[Bondo]

Does the carb need cleaning again?? When I empty the separator now it is beautiful %100 gas but did some of the crap actually make it past the separator and fuel pump filter and dirty up the carbs again?

Ayuh,..... That's my guess,.... Yer not puttin' a dumped fuel filter back on are ya,..??

Have ya changed the fuel filter since it started actin' up,..??

 

[putback]

couple things to keep in mind. If separators were 100% efficient carbs would rarely need attention. Some water in the tank after a few years is a given. Gas floats on water so most of the water always lays on the bottom of the tank. Your fuel pick up tube dos'nt go all the way to the tank bottom. What can happen, and its worse in a boat than a car, is with a tank low on fuel getting sloshed around you get a larger % of fuel contamination than with a full tank. Some water is just a fact of life & no real problem. Sometimes so much has accumulated you have to remove the tank to completely empty it. I just changed the sending unit in an old 1985 3.0 mercruiser that would throw a hissy fit now and then. Being that deep I pulled the tank and emptied it. Just shy of 2 qts of water and crud. Blew it out with a hot pressure washer, dried it. Probably had 8 hrs on it last week end and 1 fueling. No hissy fits.

 

[Fishfearme1174]

Ayuh,..... That's my guess,.... Yer not puttin' a dumped fuel filter back on are ya,..??

Have ya changed the fuel filter since it started actin' up,..??

I went with a new fuel water separator filter. The fuel pump filter is just too dang difficult to replace.

 

[NHGuy]

There was crap in the separator after the carburetor was serviced. And sure, most of it got there before the service as evidenced by the good second separator. So I see your dilemma.
I think I'd bite the bullet and clean out the tank, replace the separator again and clean out the carb again. All at the same stop. It's more work but that's the way to be certain it won't mess up things again.
And if the rubber fuel lines are old I'd change them too. When they fail you get air sucked in with the gas and the engine can lean pop at higher rpms.
If water got in the top of the carb and found its way to the float chamber the engine would run lousy too. Is it well protected from rain and splash?

 

[Fishfearme1174]

There was crap in the separator after the carburetor was serviced. And sure, most of it got there before the service as evidenced by the good second separator. So I see your dilemma.
I think I'd bite the bullet and clean out the tank, replace the separator again and clean out the carb again. All at the same stop. It's more work but that's the way to be certain it won't mess up things again.
And if the rubber fuel lines are old I'd change them too. When they fail you get air sucked in with the gas and the engine can lean pop at higher rpms.
If water got in the top of the carb and found its way to the float chamber the engine would run lousy too. Is it well protected from rain and splash?

Yes it's pretty protected from the elements. Ok guess I got some cleaning to do. So change the fuel pump filter also? But it's such a pain in the butt!

 

[Bondo]

But it's such a pain in the butt!

Ayuh,.... Welcome to the world of fixin' boats,.....

 

[stonyloam]

Yes it's pretty protected from the elements. Ok guess I got some cleaning to do. So change the fuel pump filter also? But it's such a pain in the butt!

It may be less of a " pain in the butt" to just pull the fuel pump and replace the filter on the bench, just need a new fuel pump gasket.