Help with Merc 3.0LX fuel problem

[watertoys]

I've got a '95 Sea Ray 175br with the Mercruiser 3.0LX. After 9 years,
it finally let me down last weekend. Heading back to the campsite at
3200 rpm, the engine stumbled then died. I was able to restart with a
bit of cranking, it idled fine, I got back on plane only to have it
die again after 15-20 seconds. It seemed obvious it was starving for
fuel under power, so I decided the spin-on style fuel filter after the
tank might be clogged. Since I didn't have a spare, I just bypassed it
and ran directy off the tank - the stock setup since I had installed
the extra filter shortly after buying the boat.

The boat ran fine for another 30-35 minutes, then started acting up
again. I decided to just idle back to the campsite, but it eventually
died completely and wouldn't restart. We towed it back with a 3 person
Sea Doo.

The next day I filled the tank. The engine idles fine, but it still
quits after several seconds on plane. The other thing I noticed, is
that I can hear a sucking air sound in the fuel pump vent line. Is
this an obvious sign the pump has gone bad?

I'm going to check the filter in the carb, but it should be pretty
clean given I've run a 2nd screw-on fuel filter just off the tank
since the boat was new. Is there a check valve in the tank that could
be causing trouble?

TIA for any suggestions.

-Karl

[bcha...@senconinc.com]

Karl,

I have this same problem with my 1997 Crownline 176, with Mercruiser 3.0LX. What did you find was the problem? Seems like possible contamination in the tank or fuel pump issue. Right now mine idles perfect, get up on plane perfect then dies quickly unless I throttle back to less than 3000 rpm. Then I can get maybe 1/4 mile before it dies out.

Thanks,
Bill

[H*a*r*r*o*l*d]

Hook a spare gas tank with fresh fuel to the inlet of the fuel pump and
see what happens.

[slamm...@gmail.com]

Try www.marineengine.com

YOU WILL FIND NO HELP HERE, THIS NG IS POLLUTED BY A HARRY KRAUSE, A SHITHEAD.

[Mr. Luddite]

On 5/12/2014 1:36 PM, bcha...@senconinc.com wrote:

I just read this and may not know what I am talking about but you may
have a "nest" built by some creature (bees, wasps or other insect) in
the fuel vent line. That could explain the sucking sound. It could
also explain why the engine is starving for fuel at higher RPMs. Not
enough air getting through the vent line to allow fuel to be pumped do
to causing a partial vacuum.

Don't ask me why I know this. :-)

Similar problem when running an outboard and forgetting to loosen the
vent on the gas tank.

[james...@gmail.com]

On Monday, May 12, 2014 1:36:34 PM UTC-4, bcha...@senconinc.com wrote:
> I have this same problem with my 1997 Crownline 176, with Mercruiser 3.0LX. What did you find was the problem? Seems like possible contamination in the tank or fuel pump issue. Right now mine idles perfect, get up on plane perfect then dies quickly unless I throttle back to less than 3000 rpm. Then I can get maybe 1/4 mile before it dies out.
>
>
>
> Thanks,
>
> Bill

It does sound like a fuel issue. You really can't tell anything from the fuel pump vent line unless it has gas in it, then you have a ruptured fuel pump diaphram.

The suggestion to try it with the filler cap slightly loose is a good way to make sure your vent is not clogged.

Remove and drain the big spin on fuel filter. If you get a lot of water then you probably have water issues elsewhere in your fuel system. Replace the spin on filter if you have not done that in a while.

Otherwise you probably have a leak in the line between the tank and fuel pump allowing it to suck air. Or a bad fuel pump.

Fuel problems are one of the more common problems with boats. It's only gotten worse as more fuel has alcohol in it. It's not uncommon as a boat ages for the crud in the tank to increase and some of it end up in the fuel pump. If your tank sending unit goes into the top of the tank you can take it out and look down in the tank with a flashlight. Usually you can see the water/crud "under" the gas on the bottom of the tank. If you are careful you can syphon most of it out.