2007 Mercury 115 EFI 4-stroke fuel system VST issue, pump failure, bogging, fuel loss

[JettechTN]

New member... Actually old member but they decided to scrap the old login since it was years in between logins.
I have a 07 Merc as stated above with an issue that I cant seem to get so looking for help. All the info you need is below.
Mod-115ELPT4S
Ser- 1B510416
Boat sat for about 4 years with no use. It only has 20-30 hours on it. Started with flushing the remote fuel tank, replaced primer bulb and line. Started off with clean fuel and a seafoam mix that we use with the watercraft. Motor ran for awhile on the hose until it hydro-locked with fuel due to the vac line in the VST that was cracked. Removed fuel from cylinders and removed VST and replaced the following items:
High pres pump
Low pres lift pump
Float assy.
O-rings and seals
Vac line
Both fuel filters
Injectors cleaned
Plugs
Oil & filter change
Runs great on the hose. One the lake test it runs at low speed great. At WOT it dies after 5 seconds because the VST runs out of fuel. Fill the VST again with primer bulb and run it again but it will die after it runs out of fuel unless your at wake speed to mid throttle. The filter going into the VST never stays full unless your using primer bulb. Note that the 2 pumps and float are aftermarket not OEM. One new item to add is that now after the float was replaced I will get a 5 second long buzzer and it will sound every 10 min. Any ideas before I lose my sh*t over this motor would be greatly appreciated. Thx

 

[Chicago4200]

Maybe the problem isn't with your engine. I had a similar problem and it was the check valve on the fuel tank. See the attached YouTube video

https://youtu.be/6u7elkJbNDY?t=605

 

[Faztbullet]

Run on a separate tank as either a tank/hose problem or mechanical fuel pump not working correctly...

 

[JettechTN]

Maybe the problem isn't with your engine. I had a similar problem and it was the check valve on the fuel tank. See the attached YouTube video

The reason I ruled out the anti-siphon valve is that it ran fine with out one before the boat sat.

 

[JettechTN]

Run on a separate tank as either a tank/hose problem or mechanical fuel pump not working correctly...

I have not tried another remote tank yet but the pickup is in good condition and reaches the bottom of the tank. Primer bulb and line are new but I can try to switch and run again.​

 

[JettechTN]

Does anyone think the issue is the lift pump since I went aftermarket with the brand?

 

[JettechTN]

UPDATE..Problem was the aftermarket lift pump. It would prime up the system for a min then basically fall to 50% making the vst run out of fuel. Even though you could see the fuel through the clear line we had installed it was not pulling enough volume. So the lesson is still the same to pass along, use oem parts when it comes to fuel systems and if your customer does not want to spend the coin turn them around and give a swift kick in the ass out the door. LOL. Have a nice day all.