Fuel Supply Brainteaser (Merc 5.7L)

[doehl]

Hello All,

First post on this forum. It's great, I hope to give back after getting a lot of good info reading the posts. Not new to boating, but been quite a few years so my wrenches are a bit rusty.

Just bought a 1998 Sea Ray Signature 210 with Mercury 5.7L V8 (2-barrel carbureted), Alpha One Gen II outdrive. First 5-6 times ran great (late last year), but now I'm having a problem after having it sit up for only 3 months. Boat was checked out by my mechanic prior to purchase and was given a good condition rating. Engine was pressure checked, carb adjusted, new fuel water separator installed, oil change. 30 hours on boat once I started having this issue.

Unit starts and runs for about 2-3 seconds at idle (after one pump on the throttle to max position) then dies. I was running on muffs so couldn't get a full rpm range, but I quickly tested it a couple times (few seconds) at slightly higher rpms. Engine will run if above 1500 rpms, but it's not stable (manually have to adjust throttle back after giving it a lot of fuel). But I could keep it running that way if I'd wanted to. Here's some background on my effort so far:

Engine will always start and idle, but only for 2-3 seconds before dying.
Boat was winterized, fuel stabilizer, full drain.
New fuel (93 octane) w/ water remover.
Tried running with fuel cap open, no change.
Checked strainer at inlet to carb--good.
Checked for fuel going into carb with throttle and WOT(wide open throttle) position, fuel coming in when throttle was cycled.

Any thoughts would be appreciated. Fuel pump or carburetor rebuild are the usual suspects, but I'm not sure my symptoms point directly to this issues.

Thanks in advance,

D Oehl
Jacksonville, FL

 

[coolguy147]

Re: Fuel Supply Brainteaser (Merc 5.7L)

please move to right forum

and might be carb and did u choke it?

 

[mthieme]

Re: Fuel Supply Brainteaser (Merc 5.7L)

Fuel shutoff valve all the way open?

 

[steelespike]

Re: Fuel Supply Brainteaser (Merc 5.7L)

You'll get better results in the I/O forum.
I would suspect the fuel pump or a dirty carb.

 

[chiefalen]

Re: Fuel Supply Brainteaser (Merc 5.7L)

So you already know the carb needs a cleaning, get the kit and do it.

Want to do a fuel pump pressure check you should have 4-6 psi that the pump gives you.

Good luck.

 

[Bondo]

Re: Fuel Supply Brainteaser (Merc 5.7L)

Ayuh,...

My WAGuess is,..
The Idle circuit in the Carb is boogered up,... Kit it,+ it should be OK....

 

[mountainmariner]

Re: Fuel Supply Brainteaser (Merc 5.7L)

may be a longshot, but cheap- check your distributor cap, and rotor button(or electronic ignition, whichever it has). It may,May, be restricting the spark. like I said, a longshot, but worth trying! I've seen this happen on a few different motors(non marine), Good Luck!

 

[Don S]

Re: Fuel Supply Brainteaser (Merc 5.7L)

Does this happen even if you give it some throttle to keep the revs up? If so, you may have either a faulty oil pressure switch or maybe some corroded terminals attached to the switch.
When you first start your engine, the fuel pump gets power from the starter, after the engine starts, the oil pressure switch allows power to the pump after oil pressure builds up. That way it knows the engine is running.
The switch is just above the engine mounted oil filter and has 2 terminals on it. If you turn the ignition to the run possition and put a jumper wire across the 2 terminals on the pressure switch, you should hear the pump run. If so, leave the jumper on and see if it will run ok then.

 

[sschefer]

Re: Fuel Supply Brainteaser (Merc 5.7L)

Probably has the factory Quadra Jet on it. You likely just have a piece of dirt or a little varnish under the needle seat.

Take the fuel line off and cap it then run the engine completely out of fuel. Hook up the fuel line and turn the engine over until it starts. The rush of fuel should blow whatever it is out and it will run fine from then on. If that doesn't fix it then just rebuild it. It only takes a couple of hours.

 

[doehl]

Re: Fuel Supply Brainteaser (Merc 5.7L)

All good suggestions, thanks everyone. I will be kitting the carb and checking the oil switch issue as well.

Not sure where the fuel shutoff valve is located to check it as well? Is this on the carb or inline on the fuel line somewhere.

Also, one suggestion was "to choke" the engine. I know there is a choke module right on the side of the carb, but I believe it is electronic and not sure how to make an adjustment to it if needed.

 

[chiefalen]

Re: Fuel Supply Brainteaser (Merc 5.7L)

There is not fuel shut off valve on a i/o. There is a anti-syphon valve on the tank that the fuel hose connects to and a fuel pickup tube in the tank that connects to the fitting that is the anti-syphon valve.

That all being said your lucky and Don s chimed in and i would listen to whatever he posts. And if he suggests something i would do it.

 

[StevNimrod]

Re: Fuel Supply Brainteaser (Merc 5.7L)

That all being said your lucky and Don s chimed in and i would listen to whatever he posts. And if he suggests something i would do it.

What ^^^ said, about what DonS said. Do it.

Alternatively, I'm with the group that's saying put a kit in it. Worked wonders for me...and I had all kinds of issues with keeping the thing running before the kit (which, I might add, included a new choke; not sure if they all do).