Ok, so I am finally home from hell, I mean Kuwait. Took all week to wax, clean, and install a few goodies into ole Heat, only to culminate with a trip to the lake this weekend. Bad day... ran fine all morning, went to my fave hang out spot, chiled for a few hours, went to start her up, yeah not so much. Would not idle, acted like there was a ton of air in the fuel lines. Ended up taking off the fuel filter to see what was going on, and she was down by half. Took off the inlet line from the IMCO Super Fuel Valve 3 port, and cranked her over, key in the on positionm blah blah, not a damn drop came out. I took off the panels (yes this was all on the lake) on the side on the engine compartment, there only seems to be a pickup tube, hooked to the tank selector, and a sending unit. Am I missing something? Is the IMCO part the fuel pump? Anyone have any issues like this? I have not trouble shot it fully yet, just got home after a long ass tow back to the ramp. Thanks guys. If anyone has any insight, please let me know. Oh, and even dead in the water, everybody loves the Heat lol.

The imco valve just switches the input for the pump and gauge sender from the tanks. The EFI 500 is a closed return system which means there can be vapor lock issues w that system. There is a schrader valve on the side of the fuel rail. You should put a pressure gauge on it. That's also where you bleed the fuel system. I opted for the imco 6 port switch and ran returns to the tanks

Hmmm, so the fuel pump is somewhere after the filter it seems. I will have to start diggin around more now that the engine is cooler.

Yep, it goes tank, switch, water separator, pump, rail. Then the regulator returns unused fuel from the rail back to water separator input. The pump is part of the cool fuel setup on the lower front of the engine. Below the harmonic balancer

I am gonna do a gravity feed setup (temporary) on the filter inlet and see if it will pull the fuel that way. I will grab a gauge to hook up and see the pressure. Silly intake makes it hard to see anything on top.

Hi Jay, you aren't the only person this happens too in hot weather. Ethanol blended fuels evaporate at a lower temperature than non-ethanol fuels. If you can find a station with straight gasoline in your octane requirements, you'll be much better off with hot weather starts. The other problem is the restrictive engine compartments on most Heats and Nordics. It always amazed me that these boats are literally built in a desert, and have little ventilation to the engine compart. Add the hot outside air temps to the even hotter engine compartment, and you'll have an ideal situation for hot weather stalling. It also hurts performance. I have added several air inlets to mine and it starts well hot or cold. If nothing else, just open your engine hatch when the motor is off and let the heat out.
Some other ideas, the stock gas tank elbows sometimes contain a one way ball and spring valve, that is supposed to keep gas in the fuel ines. These are always restrictive, and can gum up and clog over time. Remove them or replace the elbows. Your mechanical pull over pump may have a torn diaphram reducing flow and PSI. There is an oil reservoir in the pullover pump that needs regular oil replacement. There is a cam and armature that wears over time and can reduce fuel pressure. My engine (and I think yours too) is also equipped with a high pressure fuel filter between the cool fuel EFI pump and injectors. Change it if you haven't. The hoses that came on your boat may not be ethanol resistant, and could be flaking off internally into the filters or injectors. It's probably just hot weather and ethanol evaporation. A dash mounted fuel pressure gauge is a good addition to any performance boat.
Regards,
Steve

Cool, thanks for the tips Steve. I have an earlier serial number 500EFI it seems as it does not have the mechanical lift pump. I do have the high flow filter on the rail, I will change that for sure. I am half debating running the Aeromotive filter setup I have in the garage in it (100micron style). I have not had a chance to play with it since I brought it home. I am going to hopefully go out and play tonight. Need to refill my filter, and see what she does. It was rather hot out thatr day and the engine was suprisingly hot for one that ran for about 1 minute before it died. I had thought vapor lock out there, and foolishly listened to a gentleman out there that was a "mechanic" as well. Oh well, only time will tell. Where is this resevior in the pull over pump, or is that part of the mechanical setup you were talking about. Oh and do you have any pics of the vents you added?? I appreciate it Steve!

Hi Jay,
OK, that explains it....Texas heat, added to engine compartment heat, and no pullover pump = fuel evaporation.
When GM and Mercury first went all EFI, they thought an electric pump was adequate on their motors. That's why the GEN 6 BBCs/Mercs don't have a mechanical fuel pump boss.
It does seem to be OK on cars and trucks, because 99% of the fuel pumps are now mounted in the gas tank itself, where the fuel keeps them primed. As we all know, electric fuel pumps push really well, but they don't pull very well. Mercury later added mechanical pull over pumps to assist the EFI/Cool Fuel pumps in priming, and flowing.
Since you don't have the pull over pump, you could add one. It is now combined with the water pump into one unit. I am not crazy about this setup, but it does work. The problem I am referring to is that water and gas always get into the oil reservoir with this setup. I change mine at every 25 hour service I do on the engine and drive.
Here are some pics for you...
Regards,
Steve

Thanks Steve. I see the pump and the sea water setup will run a pretty penny to change over from the old style to the new style. I am assuming you do not want an inline pump earlier in the system pushing too much pressure into the cannister filter. I wonder if something like this would work to keep the fuel a little happier in the system.

http://www.summitracing.com/parts/MOR-65125/

That way at the very least you can have lake water temp cooling your fuel, or dump so ice water in early in the day. I will defintely be doing the vent for sure just because it needs it anyhow, maybe let that filter breath better too.

Well a "cool can" probably wouldn't hurt, but that is like treating the symptons of the problem, rather than fixing it.
What you need to do is figure out a way to keep you EFI pump primed. Maybe you could add a small adjustable output electric pump down low on a stringer so you'll have gravity working for you to keep it primed, so it can keep your EFI pump primed. Obviously you want this wired to ignition on, and ignition and kill switch off. I have done this with carbureted motors, and so have some friends, and it worked great. I have not done it with EFI. Whatever you do, make sure any (particularly pressurized) parts of the system do not leak. There's nothing worse than a fire on a boat.