Mercury 60 HP EFI 4 stroke low pressure fuel system information & test procedures

just a quick overview of the low pressure fuel delivery on this outboard. some terms may not be correct but gives a general overview of the fuel system and how to test it.

[@omieyouknowme]

One of the best explanations of how this system works. Should add if you experience furl cutting out at mid throttle and everything else checks out look at float needle. I had piece of fuel line break off plug the needle restricting fuel from low pressure pump to vst.

[@lillyautomotive]

Thank you for the kind words. Good tip to check if someone is experiencing that issue, thanks for posting. I left the VST tank out of the video because I felt like there was other videos that covered it well enough, and I didn't film it when I took this one apart. The low pressure side / lift pump side, not a ton of information out there about it.

[@omieyouknowme]

@@lillyautomotive most people automatically go to the high pressure pump. It can fail from a faulty or restricted low pressure pump.

[@joeromang703]

Thanks so much for this video!!! Your explanation confirmed my thoughts about how the system was laid out, and you supplied some much needed information for my testing. I wasgoing to replace my fuel pressure regulator while working on my VST, but that little part costs over $230, so i will be testing ig instead, first! Thanks again👍👍

[@lillyautomotive]

Glad the video helped!

[@jrmirelles4651]

Appreciate the detailed explanation best video on the topic I’ve found

[@lillyautomotive]

Thank you, glad it helped

[@2751Brandon]

Very good. I ordered a fuel pressure testing set. I been fighting this battle for a while. My priming ball went flat on me yesterday. I'm going to try an external tank.

[@richdogca]

Thanks! That is a great explanation. I've been battling gremlins in my 60HP 4-stroke Merc for a couple years now. Pretty sure it is due to low fuel pressure.

[@ftntattoo]

what a great video..thank you

[@valentinohernandez3654]

Great video with lots of information! I have a 2010 40 hp mercury bigfoot. Why would fuel be coming out of the hose you said was just for air to escape. The hose on top right beside the low pressure fuel line going into the high pressure fuel pump?

[@lillyautomotive]

This would mean the float valve in the top of the VST tank that is supposed to shut off the low pressure fuel supply is not working correctly. Either it is sticking open or the float is full of fuel

[@brettcastleberry7464]

Does the fuel make noise when the key is on? I have one and hear no noise with the key on and I can prime fuel system and get it to run for a few seconds then have to deprive it, just wondering if the fuel pump is bad

[@penstar]

Thanks mate, I've got a 2014, 60 hp Mercury efi, so this video is a great help in understanding the fuel system. You got any trim/tilt info?

[@lillyautomotive]

Nah not right now. As stuff comes in and time allows Ill film it. It'll probably be some time before I have another boat to work on.

[@dannywynn5504]

Would this cause the engine to sputter and have trouble gaining rpm?

[@matthoffman2632]

My low pressure filter, the bowl, keeps going dry after it’s running. It doesn’t seem to be affecting it doesn’t do that on my other outboard. Gaskets look fine, threads are fine. Not sure why it’s doing that, is it sucking air somewhere maybe?

[@lillyautomotive]

It could be, check for leaks on the filter bowl gasket, and try to eliminate variables. Do what you can to eliminate chunks of the system to narrow where the problem might be. Have the suction side pickup fuel from a separate container with different ( temporary line) fuel line. If it stops make sure the pickup in the tank is fully covered and there's no splits leaking air on the pickup or at any fittings. If there's no change you can test the lp fuel pump suction and make sure the needle is smooth on the vacuum guage. and not fluctuating rapidly.

[@andrew7202]

Happy I found this cuz the service manual sucks ass at describing and explaining this system. Thank you

[@lillyautomotive]

Agree, glad the video helped

[@JeremyDaigneault]

What would cause my engine to need to be primed to keep running? Idles okay but giving it any throttle i need to keep priming the bulb. Im assuming it isn't the high pressure fuel pump because it can run at WOT as long as im priming the bulb. Once i stop it starts to starve itself from fuel. Low pressure fuel pump you figure?

[@lillyautomotive]

I would say lofp. You can do the tests in the video. If you see the fuel pressure gauge bouncing that is a sure sign of the lpfp being bad. A healthy lpfp has very stable fuel pressure, it's not something I videoed but found out after replacing it. Other things could be a leak where it is sucking air. As it's pulling the fuel.

[@belowaverageoutdoorsman1193]

I have a bizarre question for you, but that motor appears to be on a fiberglass boat of some kind. I was curious what kind of speed you’re getting out of that boat I have a 60 hp on a 16’5 aluminum boat that weighs about 900 pounds and I’m only reaching a top speed of 29 mph and is a dog out of the hole ,so I’m assuming the motor is not performing correctly. I have replaced the entire fuel system on the motor except for the injectors so I’m just curious if I’m chasing a higher performance that may not be there. Hope that makes sense.

[@lillyautomotive]

It's not my boat and I haven't personally been out on it so I cant really about performance, but I did ask the owner and he said top speed is about 30 mph. It's a 2017 Mako Pro Skiff 17', online says 950 lbs.

[@ayhankucukozer1478]

Greetings my dear friend.. There is a 50 hp thatsu engine. 3 injectors are intact, the brain is intact, the fuel pump is working... but I think there is no fuel reaching the pistons. It works when I spray brake lining spray inside. I am a mechanical technician myself. Apart from the 3 injectors of the engine, there are also injectors inside the compartment called the log, I think they adjust the air and gasoline mixture. Could it be one of these? What is your advice? I wish you a good day... From Tuzla, Istanbul Greetings... Gasoline reaches the injectors. In addition to the fuel pump, there is also a pressure box that pushes the fuel forward.

[@lillyautomotive]

If the engine is running on brake cleaner, then the issue is fuel related. The injectors may not be operating, the could be clogged and spraying poorly, circuit failure, or proper fuel pressure may not be making it to them / clogged fuel filter, or screens located prior to the fuel pump. I am not 100% familiar with the engine you are asking about but I would start there.

[@jetski_tom5238]

I just put a new pump and I'm at 35 psi 😢

[@lillyautomotive]

Low pressure pump or high pressure pump ? Are you testing pressure from the Schrader valve on the VST tank? Assuming you put in a new high pressure pump and you're reading 35 psi from the Schrader valve it's possible the pressure regulator is stuck open or partially open. After you shut off the engine does the pressure bleed down? It should hold for a while. I would consider pulling apart the VST tank and in the top lid is the pressure regulator & there are a few screens (one behind the regulator too). I would clean everything and make sure nothing is blocked. Replace the regulator if pressure is low and everything is clean.

[@jetski_tom5238]

@lillyautomotive My pressure tester was faulty! Also, it was never my fuel pump. I spent $600 for nothing. It ended up being my fuel line. The lining inside was all bunched up. 😩

[@lillyautomotive]

Ah bummer that sucks! The lining inside the fuel line is why I was saying not to pinch it when testing and to pinch the line you were using to tee in the gauge, I know I wasn't super clear with that aspect but anyway atleast you found your problem.

[@jetski_tom5238]

@@lillyautomotive you're video is super helpful! Thank you!

[@lillyautomotive]

@@jetski_tom5238 Glad to hear