Mercury Engine Issues

I know somebody on here has experienced this with your Mercury outboard as I've heard this is somewhat a common issue but have yet to hear a clear solution.

Equipment: 2012 Mercury Outboard 115 EFI 4 Stroke
Problem: Engine starts fine and runs strong for about 10 seconds then really starts to stumble. Pull off the throttle and wait about 5 seconds then she builds back up and ready to go. Fills like it gets gas then runs out and has to be filled again then runs out, etc. The motor really chugs and struggles when it does stumble. It could possibly be doing just the opposite and flooding its self out but smell that way.

I changed the plugs and fuel filters. Talked to a guy at the ramp and he had something similar and ended up changing a sensor and it worked. He didn't know which sensor but said it was in the fuel separator tank. I think he might've changed the fuel float since I spoke with Chatlee and they said that might be the issue. Before I go throwing new parts on I wanted to see if any of you encountered this issue and what you did to fix it.

Last night once I was trying to return to the ramp it wouldn't start. I pulled the fuel line apart at the filter and gas spewed out like normal. Put it back together and she started and would run at 3200 RPMs.

I typically run normal gas (with Ethanol) since I use my boat a lot. I get out at least once a week or more. Boat won't sit more than 2 weeks max. I did fill it with Ethanol free gas after this issue started and it made no difference. I have no plans of ever putting Ethanol gas back in even if it has no correlation to this issue. They started selling Ethanol gas at the Sheetz near the Walmart (near Ihop) in Holly Springs before you get to Avent Ferry Road by the way.

The inside liner/layer of the fuel line(s) may have deteriorated to where they are blocking the fuel flow when under throttle. Pieces of the interior layers could be floating around, causing low fuel flow.

I had the identical issue happen to my yama 4 stroke 3 years back. Someone said float, another said fuel pump, and another said must me something fuel related at the fuel/water separator. Guess what? A simple kink in the fuel line was causing it. A $9 fix.

Check your fuel line in the cowling for kinks and fingers crossed that may be your simple solution.

I have a new 2018 Tracker boat with a 60 hp Mercury motor on it.. and they had a recall on the fuel pump I would check the fuel pump...

Thanks guys. I will certainly go end to end on the lines and see if there's anything noticeable. I opened up the fuel filters and they were clean, no dirt or any obstructions visible to the eye. Man you don't know how much I hope it's just a kinked hose.

I second what jimp said had a guy at work take it to a Marina and they redid the complete fuel system ran great for a couple days then was having the same problem you had took it to another Marina comes to find out they used a cheap line and bulb and it was losing fuel pressure.

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My 2018 Honda is in the shop right now for the same reason. Motor was running out of fuel at full throttle. Dealer kept my boat for 6 weeks when issue first started. They finally called and said come get it, its fixed. They said there was to much oil in the motor so they changed the oil and plugs. 30 seconds after putting my boat in the lake my problem happened again. I ran my motor on a portable fuel tank just to rule out motor problems and it ran fine. Actually ran off that portable tank for 4 weeks with no problems. Finally bit the bullet and took the boat back to the dealer to fix fuel problem and after a week still no fix. My boat is only 8 months old and have never put ethanol in my tank. It shouldn't be this hard. I already did half the trouble shooting for the dealer.

There is a issue with the float in that vapor separator tank that houses the electric fuel pump. Mercury has a updated float/ sensor assembly for that. Seems the float sticks on the slide causing it to run low on fuel causing that starvation problem. 2 members have had that problem on their 115 four strokes in last 60 days.

I had a 2008 mercy that did something similar. They have two fuel pumps. One to pump the gas from the tank and one to put it under pressure. One of the fuel pumps had gone bad. Very expensive. I think it was over $400 for that pump installed.

Sounds like you're losing fuel pressure or getting a fuel suckion lock. Check your fuel tank vent. Make sure your primer bulb isn't going flat.

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I'm going to remove the float switch and test it to see if it's working because a lot of stuff I've been reading points that direction. I did check all hoses for kinks and obstructions. I'll keep you posted on what I find out.

I had a similar issue couple years ago with an 05 115. Fuel lines were clogged bad due to ethanol fuel. Motor would idle fine and troll fine but when it hit about 3000 rpm wouldn't hardly run. Let off the throttle and it'd run fine. It was starving for fuel

I have had a simlar problem (Johnson 90), with the extra feature of "skipping" or stuttering at around 4200 rpms. I replaced the fuel line and pumped up the bulb to find fuel squirting from around the top of the fuel air separator. Two screws had loosened about three turns! Well, I tightened (also replaced plugs ,cables, and coils). I still have this problem. Boats are such an adventure.

I had a similar problem on my johnson 90. After replacing a couple sensors,ect it ended up being the power pack.

Did you get it fixed? Use caution when going into the float/fuel reservoir? The screws have been known to pull the threaded inserts loose. I have a 2011 115 four stroke that had similar issues. After replacing the float switch I still had issues. Turned out to be I was losing my prime by not having a hand pump that has a check valve in it. Installed a hand primer pump. Never had another issue since.

I ordered the parts and they should be in first thing next week. It is my goal to change the switch next weekend. I'm really hoping that solves it but I'll keep the primer pump in mind if it doesn't.

Sorry for the late update, I've been traveling a lot for work. Got it back on the water today and she runs great again

The problem was the float module. I replaced it and the little vent hose inside the fuel supply module. That float modue is a cheap piece of junk but it still cost me $70 then $20 for the hose and another $20 for a new cover gasket. All Mercury name brand replacements. Funny how they tell you to make sure to use genuine Mercury parts to avoid problems but it was Mercury brand that failed in the first place.

Any who, they were replaced in about an hour and she's back to where she should be.

Hope this helps anyone else that has an issue with a 2011 or 2012ish time frame Mercury motor. For around $110 and an hour of your time it will be back to new. Had I taken it to a shop they quoted around $450. Now I have $340 to spend on some new fishing tackle or just keep it for minnows this winter.

That's great to hear. Tight Lines.

Happened to me on High Rock this past May. It was the inside liner on the fuel line from the gas tank to the motor. Changed that and filters and it ran fine.

My problem has gotten to be intermittent. Runs good sometimes and other times runs out of fuel at high RPM. I started off thinking about my fuel hose but now I wonder if there is something that blocks my fuel pickup line in the tank. Worse part is I bought the boat new in November 2017 and this problem started in May. Also from Jan- April I was down with a knee replacement so what ever is wrong was probably floating in the tank from manufacturing. And my dealer had the boat for 10 weeks and can't find anything wrong.

10 weeks and can't find the problem?! Sounds like they never bothered other than maybe putting some fuel additive in the tank hoping that would resolve it. I would've lost my mind if they had mine that long and never fixed it. You should probably go straight to the manufacturer instead of the dealer. There's no way it could be your hoses at that age, I'm thinking like you and something might be clogging it up or even a loose wire somewhere that's no making a solid connection. Might even be your high pressure pump malfunctioning.