Fuel problem

[DaveinFL]

1987 classic 50 (45 HP) please read entirely.

The symptoms; Starts and runs on the water for about 50 yards, spits and sputters starving for gas. The Squeeze ball is hard until the motor quits then goes soft. Pump ball and it starts right up, rinse and repeat

What I did so far to diagnose/repair; Installed new factory fuel pump, fuel lines, filter. Vacuum tested lines and fittings by plugging intake line inside tanks (2 portable tanks) and hooked vacuum pump to intake line at fuel pump. Held 15 psi for 30 minutes. It has 7 psi fuel pressure and good flow, I didn't measure it but it runs out like a faucet. Not making any sense to me... Suggestions?

 

[Texasmark]

Going soft says it is sucking on the fuel line and can't get any flow. You either have a clogged screen in your fuel tanks, crud in your fuel line from degraded fuel inlet line (common) or your tank isn't venting or not venting adequately.

Did you happen to cut your fuel filter open to see what's in it? If tan crystalling chips, some arc'd its your inlet fuel line. If little black specks its pieces of engine fuel line.

 

[DaveinFL]

Going soft says it is sucking on the fuel line and can't get any flow. You either have a clogged screen in your fuel tanks, crud in your fuel line from degraded fuel inlet line (common) or your tank isn't venting or not venting adequately.

Did you happen to cut your fuel filter open to see what's in it? If tan crystalling chips, some arc'd its your inlet fuel line. If little black specks When the motor starts sputtering the blue is still hard

 

[DaveinFL]

When the motor starts sputtering, running out of gas, the bulb is still hard. When it quits the bulb is squeezable again. I had the fuel intakes out of the tanks and they are clear the filter on the plastic tank was already removed. The one tank is metal with a metal intake tube and a large metal intake screen, it is clean. It acts the same on either tank. I replaced the fuel lines with new. The cap vent is open and lightly blowing with compressed air goes right through. The old filter was clear and I could blow through it but since I was putting all new parts on it I replaced it also.

 

[Texasmark]

Okayeeeee.

 

[DaveinFL]

Okayeeeee.

IKR? I'm no stranger to working on these old outboards but this one has me stumped. The only thing I didn't try is testing (fuel pressure) on the water when it's acting up. On the muffs I can't get it to act up.

 

[havoc_squad]

Start with vacuum gauge T'd into fuel line going to outboard motor before it reaches fuel pump.

There should be no more than 4 inches of mercury vacuum from idle to WOT.

If you get more than that, you certainly have a fuel supply restriction where the fuel pump is struggling to get sufficient gas due to blockage/obstruction.

If it passes the vacuum test, move on to putting a fuel pressure gauge after the fuel leaves the pump T'd into the fuel line going to carbs.

Fuel pressure minimums based on running conditions have to be obtained from someone that has access to factory service manual.

 

[dingbat]

The only thing I didn't try is testing (fuel pressure) on the water when it's acting up. On the muffs I can't get it to act up.

This type of behavior is typically compression and or exhaust issues.

What are your compression numbers?

Checked your floats and needle valves for proper adjustment and operation?
A hung float or crud stuck in your float valve will return similar results

 

[racerone]

Post compression test numbers.-----You have replaced water pump impeller.-----Spark jumps a gap of 3/8" on all leads ?----Carburetors confirmed clean and not flooding ?----Checked exhaust tuner for blockage ?

 

[jimmbo]

The primer bulb should be hard, only with the Engine stopped and the Carbs filled, once the engine is running, the inlet valve in the carb will open and the Line between the Bulb and the Fuel Pump is no longer under pressure, and the bulb will be soft. If there is a restriction in the Fuel line between the Tank and Fuel Pump, the Bulb can Collapse.
Is there Fuel in the Carbs when the Engine stalls. When it dies, remove the Bowl Drains from the Carbs and see how much comes out of each.

 

[DaveinFL]

When the motor starts sputtering, running out of gas, the bulb is still hard. When it quits the bulb is squeezable again. I had the fuel intakes out of the tanks and they are clear the filter on the plastic tank was already removed. The one tank is metal with a metal intake tube and a large metal intake screen, it is clean. It acts the same on either tank. I replaced the fuel lines with new. The cap vent is open and lightly blowing with compressed air goes right through. The old filter was clear and I could blow through it but since I was putting all new parts on it I replaced it also.

Thanks for all the replies. I went back to the basics. Gotta have good compression for everything else to work right. I got a surprise when I pulled the spark plugs. The bottom cylinder shows signs of water intrusion. The spark plug had a milkshake appearance and a few drops of water on it. My manual does not give compression specifications, not that I can find anyway. I'm within a few psi of 100 on 3 of them and the last one with the water was at 93. I took the water jacket cover off and as much of the outside of the cylinder I can see looks good. It has to be getting in there somehow. Is there any other way besides a crack in the cylinder? And could this have anything to do with my fuel problem?

 

[racerone]

Check exhaust cover gaskets.