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 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.
GO BIG ORANGE !
I meant to behave, but there were just way too many other options available at the time.strmwalker LIKED above post
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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YOU CAN'T CATCH THEM ALL ......... BUT YOU SURE CAN TRY!!!!!!!!strmwalker LIKED above post
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.
Proud Member of Team Geezer
Charlie Weaver USN/ENC 1965-1979
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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