300 Weekender - Starboard engine not getting fuel - looking for advice

[joenofish]

I have an old 300 Weekender ('86), has a pair of 260 HP mercs with 700 ish hours on them. The starboard engine gets fuel "sometimes"...??? This has happened a few times, crank it up, it idles for a min or so and dies. I look in the carb while pumping the throttle and no gas is being pumped into the carb throat from the acc. pump. I pull the fuel line from the carb and crank it and no fuel. I change the filters and get a small amount of fuel, it then starts and runs normal, the next day it may or may not be in the mood to run (always the fuel issue).

I'm pointing the finger at the fuel pump (mechanical), but it seems weird to me, it should be good or bad, not hit or miss? I have never had one go bad on a car or boat but I'm sure it happens. Is there a check valve in the punp that could stick that would cause the pressure to be low or non existent? I'm picturing a rubber diaphram that either is or is not damaged..

Has anyone seen this before? I'd rather not waste $150.00 bones on a pump for nothing.

Thanks,

Joe

 

[AKBASSKING]

Well you started down the right path by changing the filters. I am assuming you mean both the fuel filter and water separator. So based on what you have posted you have to look at what is left.

1. Plugged inlet tube (inside fuel tank)
2. Plugged fuel line
3. Bad fuel pump.

If you want to troubleshoot yourself, then start with the fuel tank and work your way forward. Disconnect the fuel line at the tank and get an outboard fuel line with a primer ball. Pump into a can making sure the line is lower than the tank. Get good fuel flow? yes, move on.

Disconnect you fuel line section by section blowing them out. No obstruction, only thing left is the fuel pump.

 

[northern]

I had a fuel pump go this spring and the one failed after 25 hours. The diaphram normally goes. On the second one that went the steel plate on one side of the diaphram brock (defect) got money back as I was not in area I purchased the first one. The second time the mechanic put a pressure gauge on the fuel line when I was cranking engine. It read 4PSI the new one read 6 to 7 PSI. It has been in 100 hours and is still working well. What would happen was I would give both engines full throttle and after 10 to 20 seconds one engine would die. It ran OK up to 1400 RPM. No idea what pressure gauge would cost. It looked like a tire pressure gauge.

 

[Iprof]

Ethanol is really hard on our old gas lines, I would disconnect the line at the tank and then at the filter and use a compressor and see if you can get some air through it. I have an 88 but I have a fuel filter at the tank and another at the engine, not sure why that was done it seems like over kill to me but the filter on the tank might be a problem. If you don't look at the fuel tanks you would not know that Sea Ray used an extra 2 filters.
Checking the fuel flow first just costs you time and no parts.

Ken

 

[Pack66Dad]

Joe, I went through the same problem with my boat this year and it was frustrating. My old mechanic just threw parts at it. The new mechanic I have now found the issue right off, stuck backflow preventer. He also undid every fuel line and made sure they were in good shape with no restrictions and that my crossover valves all worked correctly.