Sporadic Miss - Vapor Lock?

First off - let me say this is an awesome site - I've read tons of posts and learned alot.
I have a 1978 SN with a 350 OMC engine. I have been chasing a number of problems this summer. My biggest concern has been this: When cold - boat runs great - no problems - but after I've run it for 30 minutes or so - come back to dock and shut her down - then idle back back out - stop to let a skier or tuber in the water - the engine will not start back - it'll turn over - just not fire - after repeated tries I can usually get her going again. At first I was thinking electrical - A prestolite breakerless ignition was installed several years ago - I replaced the coil early this summer to rule that out. I started looking at the fuel system - and have replaced everything from the tank to the carb, new fuel line (rubber fuel grade), fuel filter/water separator, fuel pump (Mallory mechanical). The carb was rebuilt a month ago. I ran it this past weekend after the the new fuel pump was installed - and she ran great - but the longer I ran it - the more problems I had - I thought it might be bad fuel - I was down to about 1/4 tank - so I let it almost run out of gas by letting it idle at the dock for 1/2 hour or so - then refilled the tank - and took off - got about 200 yards and she died - I pulled the line off the carb and no gas! Can't believe the new pump has failed already. I'm thinking vapor lock - experts please weigh in here.

I am considering the following:
1) Install an electrical fuel pump - any recommendations?
2) Relocate the new pump and fuel filter/water separator to the rear of the boat close the gas tank
3) run an insulated fuel line from the pump to the carb - any recommendations on an insulated fuel line?
4) last resort install a/c in the engine compartment - not really but have thought about a fan.

Please let me know what you think.

Thanks in advance for any and all input!!

Glen

I will say - I pulled the line off the out side of the fuel filter - and gas poured - I also sucked on the line going into the carb - got fumes at first - then gas.

have you replaced the fuel and water separator's filter lately?

vapor lock no not going to happen.

have you checked the check valve and the tank vent? are the clean?

Glen, The anti-siphon is the check valve. It's usually on the top of the tank's fuel line connection. It's a small ball check that prevents gas going back to the tank. You should have one in there but I don't think that's your problem. It sure sounds like you are sucking air someplace!

Glen, I re read the description of the problem several times and yes it does sound like you get air in the fuel line. The anti siphon to my knowledge is there so the fuel doesn't drain back to the tank when the engine isn't running. Could be it!!

Is that your anti siphon our are you just happy to see me?

Eric, Yes, I just found out the true purpose of the anti siphon valve. The good Boat Dr. just called me!!

Glen, since I have been corrected, I'd go back to my original suggestion and see what the gauge T'd into the line tells you.

The valve is there to prevent gas from being siphoned into the bilge in case the rubber line to the fuel pump fails.

It's very true that you can learn something every day of your life and still die stupid!!!

LOL - no problem 8122! I know I learn something everyday - I really appreciate everyone's input.

Thanks for clarification on the anti-siphon - I didn't have one - so I have added one at the tank. Hopefully that will correct my sporadic missing problem - and be safer if a fuel line break does occur.

I have re-worked all connections from the tank to the carb. Still no gas - so I pulled the new fuel pump and suspect it's busted - the lever that drives the pump has a whole lot more play in it than it did originally - and more than the old pump - meaning the lever will push all the way down to the housing, whereas before - it would only move maybe 1/2 way towards the housing, if that. Not sure if I installed it incorrectly, or if it was suspect from the start - strange that it ran great for a few hours before it broke. Now that I'm back to the pump, would you recommend sticking with the mechanical, or converting to an electrical? I'm leaning towards mechanical since the original last 30 years.

As always - thanks for the info!

Glen

Thanks 8122 - I'm ordering one tonight - should have it in time for this weekend and another test.