305 w/ Rochester 2bbl Stalled Dead in the Water

[dukeofwsu]

Cruising along at 2900 RPMs on plane today and the engine cut out dead. Fired it back up after about 30 seconds, ran for a couple hundred feet at a fast idle, started to push up on plane, and it died again. Got worse and worse until it only ran at idle for ten seconds or so before conking out.

Under the engine hatch, noticed the primary wire (i think that's its name) from the coil to the side of the distributor was shot. Replaced it with some 14 AWG THW stranded copper. Didn't fix the problem.

Pulled the spark arrestor and pumped the throttle and noticed the accelerator pump was spraying (with the engine off) and that the gas seemed to steam up around the butterflies. Other times fuel didn't appear to spray from the accelerator pump, though. So I was thinking clogged fuel line, bad fuel pump diaphragm, outta gas, etc.

Its got an 80 gallon alum tank, and by the gauge it was half full. Because I don't believe the gas gauge, I put two gallons in the tank from a fuel can we keep on the swim step for the dingy. No change. (I filled up after we got back and it only took 32 gal.) I pulled the filter/water separator and put on a new one I keep on board (quicksilver canister style). Ran for about 100 yards at idle, then back to nothing. By the early evening we were still 6 miles out and totally unable to start the engine.

After a tow back to the boat ramp, a trailer ride, and 32 gallons of gas, I put the plunger on the outdrive, ran the garden hose and, on the off chance I could pump a little water, I turned the key. Fired right up and ran great in the driveway. So, maybe fuel pickup or vapor lock? Maybe I really don't have an 80 gallon tank, just the sender from one... Any suggestions on troubleshooting or which thing to tear apart first?

 

[Bondo]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

Any suggestions on troubleshooting

Ayuh,... When it Quits,... Diagnose whether it's Missing the Fuel, or the Fire...

 

[dukeofwsu]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

Well, I'm ninety-eight percent certain its fuel, because it fired if i dumped a little gas down the carb. Also, as it died, coming off the throttle didn't slow the rate of stall or get it coughing along again, like it would with weak spark. Last, it has spark over while it cranks.

I'm wondering where to look first in the fuel system. In-line filters I don't know about, pickups, pump, carb, etc? I'd like to start with easiest fix/most likely and work my way to least likely/biggest pain.

Other things to note from reading other posts; One, the fuel vent line seems to breathe free when I gas it up at the pump. And when I was limping along I took the gas cap off just to eliminate a possible tank vacuum. Two, it died out quicker as RPMs/throttle came up. Idle seemed to get better results. When it did stall out, several times I noticed I wasn't getting a squirt from the accelerator pump, which suggests no fuel. I don't know if the steam around the butterflies is normal, or if that might point to warm fuel/vapor lock.

The engine and carb are vintage 1978 with FWC. It was showing decent vacuum on the gauge at the helm. The fuel pump is a mechanical and it has some sort of glass bowl filter with a brushy looking element inside that hangs off the side. I don't really know, but it looks like an old water separator. The bowl has been safety wired to not drain by someone previously. The newer canister style fuel filter/water separator is mounted under the heat exchanger, ahead of the pump on the starboard side.

 

[Rippenlips]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

Vapors from the inside of the carb is normal on a hot engine. I would look at the fuel pump. Put a clear filter inline next to the carb or fuel pressure gauge and make sure it stays full of gas. I use a cheap oil pressure gauge. If the engine dies and there is no fuel in it its upstream. sounds like you checked everything else.

Jon

 

[zbnutcase]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

You might also pull the pickup tube out of fuel tank and see if there is a plugged filter screen on the end of it-seen it many times in my 23yrs as a marine tech. 'nutcase

 

[dukeofwsu]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

Just came in from pulling the fuel system apart. Here's what I've found so far;

The screen at the carb is clean. I emptied the fuel water separator canister into a jar and the fuel is uniform amber color, no sign of water. The shutoff valve is in good shape. The check valve operates if I blow into it with cheeks about half puffed (kinda makes a gurgle stuttering as it rapidly opens,pressure drops, it rapidly closes, etc). The pickup had a little gunk on the screen, not much though, and it easily flicked off.

The pickup down-tube is an area of interest. It slips on the barbed end of the elbow going into the tank, just a pressure fit. Its a hard, translucent orange plastic, and it appears to be a little deformed at the barb fitting on top. I'm wondering if its getting some air leak here, and as tank level drops, it takes more lift/suction, which pulls more air in and loses prime. Anybody think that could explain why its not an issue on a full tank, but shows up at 2/3 a tank?

Also, while I have it apart, can anyone talk me into or out of replacing the fuel pump. I have service records from the previous owner going back to '92 and I can't find a replacement history. My thought is, its due, but those flare fittings are gonna be pretty unhappy about being torqued on.

 

[dukeofwsu]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

So, a few months down the road, I've replaced the fuel pump, replaced the points with a petrontix, done the tune-up, and been out using the boat.

The other day I was down to a half tank, running along at 3200 rpms, engine a little warm at 190 or so (FWC) and it dies like I'd turned the key off.

Vapor lock, loose connection on the primary wire somewhere in the loom between the choke and the coil? Why am I only seeing this on a half tank, bad luck?

 

[havasuboatman]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

Was the water seperating fuel filter full of gas when you took it off, or was it only about half full? This makes a big difference as to where you should look next.

 

[jerryjerry05]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

Sounds like a coil.J

 

[mkast]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

Have you tried following the troubleshooting section in the appropriate maintenance manual?

 

[robjen1019]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

wondering if the pickup hose in the tank has something wrong with it. Might be sucking air at half tank.

 

[FreeBeeTony]

Re: 305 w/ Rochester 2bbl Stalled Dead in the Water

You can also try running it off a seperate tank to see if it's a problem in your main tank.