I have 2 454 mag mpis that I ran the return lines back to the tank. Last year I was in AL and needed fuel so I could only find ethanol fuel and I had vapor lock to some degree. She cranked but barely idled and died with any throttle till it filled filter and then ran fine again.

Well, it did it last weekend, I fueled up during January at the same non-ethanol station, but I am guessing they switched the fuel on me since it started doing it again.

I figure I will just add the fuel pump booster that I had purchased on my 25 ol but dont want to spend $300 a kit when I can just buy some Holley, etc. marine booster pumps.

Question: What psi do I need to pump fuel from tank to filter head??

Thanks

Your problem is Jan / winter fuel blends. it all has to do with RVP = Reid vapor pressure of the fuel (volatility) and is EPA regulated. Google it and read away. You need to buy fuel during the season you are boating timeframes. RVP is taught especially in all Mercruiser training schools. I have reported about this up here if you want to search.

Hawaii is the only state in the nation that RVP is the same 365 day per year - WHY because their temps do not change very much at all. 68 to 85 deg all year long. Other states (weather temp changes) change RVP values 7 times per year every year like clock work. Some states change it 3 times per year.

RVP of the fuel has a lot to do with vapor lock to.

With that said - Mercruiser sells a complete boost pump set up kit and helps against vapor lock. If you need one let me know and I will try to beat or match pricing within reason. Info in the link below

http://www.fidibuy.com/product/detai...7-502-Mag-MPI?

http://www.epa.gov/oms/fuels/gasolin...lity/index.htm


http://www.epa.gov/oms/fuels/gasolin.../standards.htm



An somewhat the jist of vapor lock and RVP from PPT copy from Merc and the Mercruser service bulletin about vapor lock and RVP.

read this as I have posted it before.

https://www.perfprotech.com/blog/art...ser-vapor-lock

mercruiser SB -

http://www.boatfix.com/merc/Bullet/99/99_07.pdf

A good watch for whomever and another reason NOT to run 6 month old gas. 30 days max especially for High compression and or high hp engines.

https://www.youtube.com/watch?v=JtSVUzk8obI

part 2

https://www.youtube.com/watch?v=0tCi9x2WXCE

part 3

https://www.youtube.com/watch?v=JOIOttjdduA

Thats interesting, I had heard of winter mix but didnt think it would cause my mild vapor lock issue. Thanks for info BUP.

Do you know what the fuel pressure is needed by a booster pump?

I had kit on my last 454 mag (25ol) and it worked fine for the first season. It locked up after my 1st winter, so rather spending $4-500 for 2 kits, I figure I would just by aftermarket pumps (holly or etc).
thanks

Most stock marine engines that are using a boost pump range around 6 to 12 psi.

that Mercruiser kit that I posted retails for $ 490 so 2 complete boost pump kits would be under a grand - they come with the wiring harness, bracket and everything else needed to plug and play. I could sell 2 kits under 900 bucks shipped all brand new complete, just saying.

the key to get longevity from electric fuel pumps is quality filters changed often along with fuel samples and using fresh gas plus when the boat is stored or lay up more than a month proper winterizing / or lay up of the fuel system. The trick is 2 stroke outboard engine oil and a really good fuel stabilizer mix..

Well, I ran it again and it vapor locked. Evidently, the winter I fuel I have in her is causing it to vapor lock. It still cranks and idles, but stumbles due to filters half empty. (vapor lock)

I wasnt going to buy kits, but after running last weekend and letting her breathe for 5 minutes with hatch up, she still locked!!
So after cutting finger on belt while messing around in bilge, I ordered some parts!! (3 stitches on thumb from serp belt/pulley...oops)
2- Red Holley Marine (7psi)
2- Holley inline filters
assorted inline fuse and parts.
(have to clean bilge next!!!)

[ATTACH=CONFIG]543206[/ATTACH][ATTACH=CONFIG]543207[/ATTACH][ATTACH=CONFIG]543208[/ATTACH][ATTACH=CONFIG]543209[/ATTACH]

Okay people, answer me a question - the Merc electric 'boost a pump' is before the fuel water seperator right ?