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HP 500 EFI Vapor-lock kit

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Old 12-13-2003, 02:53 PM
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Default HP 500 EFI Vapor-lock kit

I bought 2 of the Merc retro-fit kits for my 1999 500 EFI's.

Kit includes an one-way valve to prevent water from draining out of the block when the motor is not running, and an electric fuel pump to be installed prior to the fuel filter.

My mechanic thinks the one-way water valve will cure my vapor-lock problem, and that the second electric fuel pump isn't necessary because all it can do prime the existing fuel pump.

What do you guys think?

Has anyone installed the kit?

Do the post-1999 HP EFI's come with 2 fuel pumps?

Thanks for any help you can offer!
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Old 12-13-2003, 03:15 PM
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I "believe" I have just purchased the same kit on E-Bay. Obviously not installed yet. I have had a considerable problem with vapor lock (2000 - 500 E.F.I.s) on the port motor. The search portion of this site will reflect numerous other confirmations that the kit will work. I made a recent inquiry that "Trouty" answered, again with praise to the kit. According to Merc. the 2 fuel pump models started in late 2001-2002 and the problem has been eliminated. I would also be interested as to the method/difficulty installing the kit.

Also, I did isolate some of the problem, appears to be based on where the fuel was purchased.

Lets PLEASE keep each other posted.
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Old 12-13-2003, 04:46 PM
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Okay I have to ask. Why is an EFI engine having vapor lock problems? Doesn't the fuel system have a return? In all of my years i have never heard of a modern fuel injected engine having a vapor lock problem. Please explain to me exactly what point in the fuel system is vapor lock taking place.

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Old 12-13-2003, 04:57 PM
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Yes, there is a return.

I have no idea why the problem existed with the first production of this motor.
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Old 12-13-2003, 05:49 PM
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No, there isn't a return, at least not one put in by an OEM, not if it is coast guard certified. And that is why it is a problem with all Mercs EFI engines, not just the 500. Hence Cool Fuel and other fixes from Merc like letting it idle to cool down, keeping the hatch open when stopped to let heat escape and so on...it is a well documented problem.

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Old 12-13-2003, 05:58 PM
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So these kits are for pre 2001 fuel cool systems?

Mine has the fuel coolers and the by pass goes back to the fuel water seperator.
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Old 12-13-2003, 09:19 PM
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Its my understanding the problem was significant enough that the factory has since gone to the the mechanical fuel pump back on the water pump, AND the electric one located with the cooler under the motor 2001+. The fix, other than changing out the older water pump to the new model w/the fuel pump, is this retro kit. Please help, are we on the right track, and as Apache Pete as referenced, those that may have completed this retro, how difficult, and any pointers.
Thanks
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Old 12-14-2003, 02:23 PM
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ttt
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Old 12-14-2003, 10:13 PM
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Troutly,

Thanks.

Nice new avitar!
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Old 12-18-2003, 05:54 PM
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Update. Please help guys. I have received the correct retro kit as provided by Merc., instructions are vague at best. Particular confusion with the anti siphon valve, says to change existing one (where is this one) with a provided electric one. Also, I could use further clarification regarding the provided wiring harness. The new pump is appears pretty easy. Any help would be appreciated.

Thanks
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