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Joe
Joe, Marine Mechanic
Category: Boat
Satisfied Customers: 7246
Experience:  ASE, electronics, Marine mechanical and electronics, pwc, wiring, all around repair tech,
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My 4 winns 5.0 L stalled in no wake zone after sitting in

Customer Question

Hello.
my 4 winns 5.0 L stalled in no wake zone after sitting in the swim zone for about an hour.
I replaced the cap and rotor and spark plugs due it happenING 2 weeks ago.
I treated the tank with sea foam and put 93 octane gas in the tank.
I am thinking it might be vapor lock but I'm not sure. The boat would fire momentarily and the die.
after many tries it finally started when I kept the throttle wide open until it started.
Then it ran fine....thus unreliability is bothering me.
It is a EFI ford 302 omc cobra volvo sx.
any help is much appreciated.
thank you
Mike
Submitted: 1 year ago.
Category: Boat
Expert:  Joe replied 1 year ago.
Hello,
Thank you for allowing me to assist you, my name is ***** ***** I will be happy to assist you with your concern today.
Best thing to do is start with the basics, during the problem esp no start, check spark and make sure not loosing it causing it to die, this means it can have spark and the next min not, if not spark then next attach a fuel pressure tester and check fuel pressure... this is a more common problem than others for this to occur because of fuel and thus best to start here, you may very well find little or no pressure or pressure not holding which could be regulator, leaking injectors, bad/failing fuel pump, starvation, vapor lock, etc. If fuel pressure if fine then you would want to check injector pulse and if good and spark is good next checking timing and if dist and cap are tight and timing is correct next check compression just to be sure working with a good engine. From here would need to start checking sensors which would help via a scan tool.
A worthwhile notation, holding throttle wide open since fuel injected all you are doing is giving the engine more air (until engine starts and see where throttle is from tps and gives fuel accordingly that is. This could then mean it is actually getting too much fuel and or bad fuel and the extra air is helping to start, however, iac and tps would need to also be checked/tested to make sure they are not the problem.
This gives you a place to start and we can continue after the above or as you have further questions either way.
Thank you!
- Joe
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