60hp 4 stroke shuts down above 3000 rpm

[fm160]

2011 60 hp EFI Bigfoot on a 20' pontoon. Into the shop multiple times. Replaced fuel line, impeller(not related), fuel filters, spark plugs, low pressure fuel pump, high pressure fuel pump, new screens in VST. Starts and runs perfect at low speed. Will run at WOT for a couple minutes, then starts shutting down and won't go more than around 2000 rpm. Runs longer before shutdown if at 3000. Just ordered a fuel pressure test kit but believe mechanic already checked. Problem surfaced 3 years ago. Mechanic replaced high pressure fuel pump with aftermarket pump, set off alarms. Old pump back in, everything okay last year. This year same problem back with shutdown. DIY now replaced high pressure fuel pump with OEM part. Replaced O rings on fuel cooler mounted on side of VST (leaking fuel). Lake test yesterday, same problem.

 

[QBhoy]

Hi. You sure it’s maybe not loosing water pick up (just being sometimes and issue with pontoons and an engine that’s maybe not set up well on the back) and overheating, alarming and going into guardian mode ?
Failing that…is it maybe having issues with the neutral safety switch ?

 

[fm160]

Thank you for the reply. New impeller installed a couple years ago and high volume of water out the pee valve. Have not monitored it at speed, will do that. No alarms for over temperature and high water volume led me to dismiss a blocked intake or thermostat but will monitor water discharge at speed. Neutral safety switch is something I have not investigated but will see if I can find a connector and disconnect it after starting the motor.

 

[fm160]

Looks like the coil wires are reversed on cylinders 2 &3. There are misc numbers printed on the block, but cylinder order from varous youtube videos indicate 1-4 from top to bottom. Would reversing 2 &3 still run good but shutdown under load at higher rpms?

 

[QBhoy]

Looks like the coil wires are reversed on cylinders 2 &3. There are misc numbers printed on the block, but cylinder order from varous youtube videos indicate 1-4 from top to bottom. Would reversing 2 &3 still run good but shutdown under load at higher rpms?

No. Would say that it would struggle to run at all. Missfiring, popping all the time, even if it did manage to run.

 

[QBhoy]

Have a look at the neutral switch in the control box. Also the trim limit switch

 

[fm160]

No. Would say that it would struggle to run at all. Missfiring, popping all the time, even if it did manage to run.

Turns out cylinders 2 and 3 must be paired up because swapping the coil wires to the plugs made no difference. Fresh set of plugs, new thermostat, bypass neutral safety switch, no difference. Connected portable fuel tank to bypass onboard fuel tank, and it would run if you kept pumping the primer bulb, so still a fuel issue. Second time we have tried this in two years and both times using the portable tank must have damaged the diaphram in the low pressure pump because now fuel pump leaking fuel when pumping bulb and will not pump up hard. Frustratrated with this motor. Low pressure pump on order but still may not fix anything.

 

[2ltime]

I had a 2003 that did the same thing. The low pressure pump, pumps into a chamber containing the high pressure pump. The flow into this chamber is controlled by a float valve similar to those found in a garden tractor engine. The float opens a needle and seat type valve. My engine had a piece of crud/corrosion blocking the passage above the needle/seat not letting enough fuel in for high throttle use. The boat would go slow, open throttle and everything was fine for a few minutes until that chamber emptied, engine would struggle at low RPM, chamber would fill back up and boat would take off again for a few minutes.

 

[fm160]

Thank you for the reply. I had the VST apart and replaced the high pressure fuel pump, bottom screens, and rubber hose from pump to outlet. Looked at the float to verify it worked, and moving it up and down blocked or allowed me to blow through the inlet tube. Did not replace the seat as it was not part of the fuel pump kit. Low pressure pump due in tomorrow and I will again hook up portable tank to eliminate onboard tank. Also ordered a 12v transfer pump and some inline filters and will try to clean the onboard tank if any junk in there. Hard to use up all the fuel and replace in onboard tank. New pickup tube also on order. Throwing lots of parts at this problem, but nothing has fixed it so far. Will look for a new seat for the float. Any thoughts on the fuel pressure regulator in the VST, about the only thing I haven't replaced in the fuel system, but $250 and not sure how to test if old one is bad. Thanks.

 

[Ken Kitchen]

2011 60 hp EFI Bigfoot on a 20' pontoon. Into the shop multiple times. Replaced fuel line, impeller(not related), fuel filters, spark plugs, low pressure fuel pump, high pressure fuel pump, new screens in VST. Starts and runs perfect at low speed. Will run at WOT for a couple minutes, then starts shutting down and won't go more than around 2000 rpm. Runs longer before shutdown if at 3000. Just ordered a fuel pressure test kit but believe mechanic already checked. Problem surfaced 3 years ago. Mechanic replaced high pressure fuel pump with aftermarket pump, set off alarms. Old pump back in, everything okay last year. This year same problem back with shutdown. DIY now replaced high pressure fuel pump with OEM part. Replaced O rings on fuel cooler mounted on side of VST (leaking fuel). Lake test yesterday, same problem.

I may just be a kid, but, to me it sounds like a venting problem. I'd check the fuel tank vent..

 

[fm160]

Thank you for the suggestion, I had not thought about the vent. Will check it tomorrow when I get there.

 

[tphoyt]

I may just be a kid, but, to me it sounds like a venting problem. I'd check the fuel tank vent..

Nothing wrong with being a kid.
Don’t hesitate to toss out your thoughts and ideas. That’s how we all learn.
Best

 

[fm160]

Absolutely true, toss out the ideas because no-one has all the answers. Thankful for any help I can get or suggestions I haven't tried.

 

[kbonanny]

How's the vent? I encountered this very same issue 1 or 2 years ago that 3 different Marinas missed. The vent on the one I worked on was blocked with a bee nest. I HATE bees! Got stung 32x as a 13 year old going to the bathroom in the woods...stung in ALL of the WRONG areas! I managed to hobble with my pants half off to a creek a good 75 feet away and dove in and those little bastards were STILL stinging me! Needless to say, I HATE bees! I almost burned my house down trying to burn a nest in a rain gutter...thankfully my hose was close by and I didn't pour that much gas down the spout! It did kill the pricks, but also caught my shingles on fire!!! I was able to extinguish it with minimal damage...didn't even have to replace the shingles. I normally never do anything "stupid" like that but again, I HATE bees!

 

[fm160]

Removed the vent hose on the top of the built in tank and could blow through it with the fill cap closed. Did not seem restricted at all. Installed new low pressure fuel pump and added a clamp where one was missing on a fuel line, but not leaking. Was not able to water test yet. Noticed the clear bowl on the low pressure fuel filter would fill up when pumping primer bulb but fuel would drain out when running and not remain full. Read somewhere this is normal, just seemed wrong. Plan to replace fuel pick up tube next week, and run an external pump and filters to cycle and clean any debris in tank.

 

[KJM]

I once had a similar problem that turned out to simply be a kink in a flexible fuel line that was restricting gas flow but not entirely shutting it off. Rerouted the line and no problems since.

 

[fm160]

Latest update. Ran an external 12v fuel pump with in line filter and recycled the fuel from the pickup tube to the gas cap port for two hours. Added more fuel and fuel conditioner, ran another hour. Removed pickup tube to check for strainer intact and clean and it was clean. Removed check valve at top of pickup tube and replaced with straight fitting. Ran again with 12v pump to check fuel flow. Fuel flow noticeably higher volume without check valve. Reconnected fuel line with bulb, no change in volume. Seems check valve on pickup tube restricting fuel flow. Now with new low pressure pump and no check valve, motor ran at 3000 rpm for 20 minutes with no issue. Previously motor would shut down after 3 minutes. Since there is a check valve in the bulb, is a second one necessary on the pick up tube? Motor is running good now. Fingers crossed.

 

[KJM]

Latest update. Ran an external 12v fuel pump with in line filter and recycled the fuel from the pickup tube to the gas cap port for two hours. Added more fuel and fuel conditioner, ran another hour. Removed pickup tube to check for strainer intact and clean and it was clean. Removed check valve at top of pickup tube and replaced with straight fitting. Ran again with 12v pump to check fuel flow. Fuel flow noticeably higher volume without check valve. Reconnected fuel line with bulb, no change in volume. Seems check valve on pickup tube restricting fuel flow. Now with new low pressure pump and no check valve, motor ran at 3000 rpm for 20 minutes with no issue. Previously motor would shut down after 3 minutes. Since there is a check valve in the bulb, is a second one necessary on the pick up tube? Motor is running good now. Fingers crossed.

Sounds like you may have finally found your problem! Sucks that you had to spend money on unnecessary replacement parts. After all that work, I'd probably put a new check valve back where the original was, I don't imagine they are that expensive. Then at least everything would be back the way it was designed to be. Good luck!