99 5.0 EFI Wouldnt run after sitting, Vapor Lock???

bowtie4x4295

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Joined
Jun 9, 2008
Messages
45
99 Marada, 5.0 EFI 137 hours, full tank of fuel.
Take the girls from the softball team out after practice the other day. We ride for 10-15 min and stop to let them swim. One of the girls had never been boating and wanted to ride, so we load back up and ride for approx 20 min DOWN river. They want to swim again, so we stop in large part of river,eat some sandwiches and let the engine idle so the girls could listen to radio not to far from shore and let them swim. Storm shows up on herizon, time to go. Boat cranks fine, idles fine, I hit the throttle she surges a bit and dies. Crank her back up, hit the throttle, dies. Now she wont start at all. Acts like she wants to, but not quite, we are stuck.
Nice people come by tow us several miles until the friend i called arrives, we get it to ramp and on trailer. Go out this morning to get serial number from engine to look for fuel pump and say, what the hell and give her a spin. She fires right up, shut it down, hook up the muffs crank her right back up, now she is running like new again. I have never had an issue with this boat at all, so I figure it is time, but now I dont know what to fix. Could this be a vapor lock, have read there is some issues with this and engine compartment temps. Now thinking of installing some fresh air vents on the side to increase air flow. Just kind of at a loss right now. Kinda embarressed in front of my girls, and dont want their parents to worry about them when the are in my care.

Thanks for any help or insight, Mike
 

Bondo

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71,082
Re: 99 5.0 EFI Wouldnt run after sitting, Vapor Lock???

I have never had an issue with this boat at all,

Ayuh,... Vapor-lock doesn't Just appear on a decade old boat...

I'd sooner think it's Crud in the Fuel....
Check the contents of the Filter....

Has it been tuned up in the last 11 years,..??
 

QC

Supreme Mariner
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Mar 22, 2005
Messages
22,783
Re: 99 5.0 EFI Wouldnt run after sitting, Vapor Lock???

Vapor-lock doesn't Just appear on a decade old boat...
Did on mine . . . and the symptoms and circumstances were very similar. If you let her sit for two hours, all good. Based on the Merc memo I'm thinking ethanol content + weak impeller (flow to cooler low) made the difference. Have not had the problem since I replaced the impeller. Repeated three times the day before.
 

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Bondo

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Staff member
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71,082
Re: 99 5.0 EFI Wouldnt run after sitting, Vapor Lock???

Did on mine . . . and the symptoms and circumstances very similar. If you let her sit for two hours. All good. Based on the Merc memo I'm thinking ethanol content + weak impeller (flow to cooler low) made the difference. Have not had the problem since I replaced the impeller. Repeated three times the day before.

Ayuh,... Then I'll defer to yer Experience, QC... ;)

It wouldn't surprise me, as the number of fuel related Problems in my life has gone to the Moon, in the last few years...
I know Gasoline ain't really Gasoline anymore,...
Still smells sorta the same, but don't act like it used to...

Wish I had more Diesel powered toys,... :D
 

bowtie4x4295

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Joined
Jun 9, 2008
Messages
45
Re: 99 5.0 EFI Wouldnt run after sitting, Vapor Lock???

Before I go out the first time for the season, I carry it to get it tuned up. So it gets it annually, whether it needs it or not. I keep reading about a one way valve that stops hot water from running down to the fuel cooler that helps alot. merc/quicksilver # 21-862271A. Aslo for got to add that the temp outside was 95-98 and the heat index was 110. So it was HOT.

Mike
 

bowtie4x4295

Seaman Apprentice
Joined
Jun 9, 2008
Messages
45
Re: 99 5.0 EFI Wouldnt run after sitting, Vapor Lock???

Anyone ever try this valve?

mike
 
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