GatorJ Posted July 18, 2022 Report Share Posted July 18, 2022 I have a 2002 90hp Yamaha and hoping for some ideas as to what may be causing a new, semi-random / semi-repeating fuel issue that acts like it is starving for fuel and eventually stalls. I am running non-ethanol gas treated with Yamaha Ring Free as well as Sta-bil. Gas is about 4 weeks old. Even after sitting for multiple weeks, it startes right up and idles fine for as long as I want, be it hooked up to the water hose at home or in the water at the ramp. So here is what is happening the last three times out. Whether after I start it at the ramp or after fishing a spot and moving to another one, shortly after putting it in gear (anywhere from 25ft to 200ft) it starts to act like starved for fuel and one after another cylinder drops out until it stalls. I pump the bulb, it restarts immediately and idles good and then it is fine and I can hop up on plane no problem. The first time this happened, once on plane it ran great the entire way back to the ramp and for reloading. Second time out, when ready to call it a day, it did the same start / idle a little way / stall / restart / get on plane no problem thing, but half way to the ramp it started to act like starving for fuel a couple times briefly then picked back up and ran the rest of the 14 miles to the ramp without issue. Once back to the marina, it idled great to the dock and I shut it down to get trailer to the ramp. Started up fine, but after motoring maybe 25ft towards the trailer is starved for fuel and stalled, but after a few squeezes of the bulb it started up fine and got on the trailer. Once back home, I installed a new big spin-on water separator filter, hoping that was the issue. Third time out, same start / idle a little way / stall / restart / get on plane no problem thing, but after calling it a day, this time after heading to the ramp and running about 3 miles on plane at 4500 rpm, it starved and stalled, pumped the bulb and restarted, got on plane and ran fine the rest of the way in. Did the same starve thing moving from dock to ramp. Any thoughts as to what may be the culprit? I am about to order and new fuel hose / bulb / engine connection assembly as well as a new engine filter element / o-ring / clear filter bowl. Hoping it is one of these components that is causing the issues. With it being semi-random, and mostly happening at low speeds but now starting to happen at high speeds, it has me baffled. Thanks in advance for any input. Robert Quote Link to comment Share on other sites More sharing options...
Lap it Up Posted July 18, 2022 Report Share Posted July 18, 2022 I would start out with the primer ball. I like the mercury version since they have a two way check valve and don’t have to be mounted vertical like the Yamaha ball. If you haven’t changed your fuel pump in a while it may be time to replace new. Even if it isn’t the issue it’s nice to know you have a brand new diaphragm pump. Make sure to buy an OEM Yamaha fuel pump. They are much better then the Sierra copy. 1 Quote Link to comment Share on other sites More sharing options...
SCFD rtrd. Posted July 20, 2022 Report Share Posted July 20, 2022 If the above doesn't fix your problem. I would suggest replacing the anti-siphon valve. It's located on top of the fuel tank near your fuel sending unit. It can produce all the symptoms you describe. 1 Quote Link to comment Share on other sites More sharing options...
Wanaflatsfish Posted July 22, 2022 Report Share Posted July 22, 2022 On 7/18/2022 at 3:03 PM, Lap it Up said: I would start out with the primer ball. I like the mercury version since they have a two way check valve and don’t have to be mounted vertical like the Yamaha ball. If you haven’t changed your fuel pump in a while it may be time to replace new. Even if it isn’t the issue it’s nice to know you have a brand new diaphragm pump. Make sure to buy an OEM Yamaha fuel pump. They are much better then the Sierra copy. 20 year old engine....I agree...only difference is I would get the fuel pump diaphragm assembly.....less to go wrong and a few $$ more. On 7/20/2022 at 4:56 PM, SCFD rtrd. said: If the above doesn't fix your problem. I would suggest replacing the anti-siphon valve. It's located on top of the fuel tank near your fuel sending unit. It can produce all the symptoms you describe. Yes....it's not uncommon for them to clog...same thing on my skinny mini 17T with a 1998 50 hp 1 Quote Link to comment Share on other sites More sharing options...
fin-addict Posted July 22, 2022 Report Share Posted July 22, 2022 Agree with the primer bulb first. Happen with a friends while I was on it. Hose clamp loose and sucking air. 1 Quote Link to comment Share on other sites More sharing options...
GatorJ Posted August 20, 2022 Author Report Share Posted August 20, 2022 Thanks for all the inputs. As a start, I replaced the spin-on water separator fuel filter, fuel hose / bulb assembly as well as the small fuel element on the engine. All of that reduced the number of times it starved and stalled to one time in gear going slow and one time at speed during an extended test run. Next up will be replacing the fuel pump & gasket with an OEM one. I figure I might as well replace all the hoses between the engine cowl quick disconnect and the carbs. Between the 20 year age and the excessive heat in coastal Louisiana, figured they are overdue for replacement. Quote Link to comment Share on other sites More sharing options...
searing Posted September 7, 2022 Report Share Posted September 7, 2022 Hi GatorJ, Thank you for creating this topic. Just today I experienced identical symptoms as you described with my own 2000 Yamaha 90hp. As soon as I would pump the ball it would run perfectly for a while or until it sat for a while fishing. I'm thinking it would have to be that it's sucking in air from somewhere. I'm going to start with an entire new fuel line and all that's in between the fuel tank and the motor due to the age of everything. Please post if you found the cure for yours and I'll do the same. I should get to it in the next week. Quote Link to comment Share on other sites More sharing options...
searing Posted October 24, 2022 Report Share Posted October 24, 2022 On 8/20/2022 at 12:27 AM, GatorJ said: Thanks for all the inputs. As a start, I replaced the spin-on water separator fuel filter, fuel hose / bulb assembly as well as the small fuel element on the engine. All of that reduced the number of times it starved and stalled to one time in gear going slow and one time at speed during an extended test run. Next up will be replacing the fuel pump & gasket with an OEM one. I figure I might as well replace all the hoses between the engine cowl quick disconnect and the carbs. Between the 20 year age and the excessive heat in coastal Louisiana, figured they are overdue for replacement. Boat and motor at 22 years old I replaced everything that fuel passes through from the tank connection to the carbs. The last thing I removed to replace was the fuel pump only to find it wasn't even tight. Wished I checked it first. I replaced the fuel/water filter bracket and hose fittings all stainless, and the Raycor style filter with the clear bowl. I found that the old filter which was new in April with maybe 25 hours since was full of water. Super glad the filter was doing it's job. I may see about having the tank emptied and flushed, until then I'm keeping a good eye on the filter bowl. I wish I could have replied as I said I would with a single cause for the issue but in my case I think it was several issues. Motor is running great now. I've only owned this boat since May and prior to this intermittent starving issue I actually thought it might be over propped because 4800/4900rpm was max fully trimmed, now it'll run 41mph @ 5500rpm with just me loaded with gear, 3/4 fuel, and full live well. I hope you were able to get yours figured out. Dennis Quote Link to comment Share on other sites More sharing options...
GatorJ Posted January 18, 2023 Author Report Share Posted January 18, 2023 My issue seems to have been either the original fuel pump mounting bolts having been semi-loose or the pump diaphragms failing. After a new OEM fuel pump and gasket installed and tightened, the engine runs perfectly, purring right along as it did when new 20 years ago Quote Link to comment Share on other sites More sharing options...
searing Posted January 22, 2023 Report Share Posted January 22, 2023 On 1/18/2023 at 12:53 AM, GatorJ said: My issue seems to have been either the original fuel pump mounting bolts having been semi-loose or the pump diaphragms failing. After a new OEM fuel pump and gasket installed and tightened, the engine runs perfectly, purring right along as it did when new 20 years ago Great news!!! Mine is running better than ever too. Unfortunately I'm still dealing with something that causes a loss of pressure in the fuel line. It's intermittent and nothing that a few quick squeezes of the bulb doesn't take care of instantly. I hope I can find the cause, I've already replaced so much related to fuel starting with the pickup tube all the way to the carbs.:( Quote Link to comment Share on other sites More sharing options...
GatorJ Posted January 22, 2023 Author Report Share Posted January 22, 2023 2 minutes ago, searing said: Great news!!! Mine is running better than ever too. Unfortunately I'm still dealing with something that causes a loss of pressure in the fuel line. It's intermittent and nothing that a few quick squeezes of the bulb doesn't take care of instantly. I hope I can find the cause, I've already replaced so much related to fuel starting with the pickup tube all the way to the carbs.:( My symptoms were intermittent as well. After start-up, it would go anywhere from 25ft to 100 yards then starve and stall. Pump it up and I could run 7 miles to a fishing spot without incident. Then, in addition to the initial start up, I could run 5 miles smoothly before it would starve and stall. Pump the bulb up and off I would to for another long haul. There was no rhyme or reason, or consistency as to air temp, water conditions or distance run. I too changed spin-on and engine fuel filters (engine filter looked like new, didnt even have any fuel discoloration to the plastic), changed the fuel line / bulb assembly and connections with OEM parts, checked all the engine hoses and small fittings too. The fuel line / bulb assembly was an aftermarket replacement done 7 years ago. That particular hose had the clear plastic liner which was starting to detach from the hose interior which would / could cause a partial blockage or flow reduction. After replacing it, the boat ran a bit better but still had the random fuel starving / stall issue. Once I replaced the loose fuel pump with a new OEM fuel pump and gasket, the problem went away. Have you checked that the fuel pump is tight? My fuel pump was the original 2002 one, so the diaphrams / valves may have been starting to deteriorate some. I dont know if it was the pump itself, or it having worked loose a bit, but the engine runs like new now. Quote Link to comment Share on other sites More sharing options...
searing Posted January 23, 2023 Report Share Posted January 23, 2023 14 hours ago, GatorJ said: My symptoms were intermittent as well. After start-up, it would go anywhere from 25ft to 100 yards then starve and stall. Pump it up and I could run 7 miles to a fishing spot without incident. Then, in addition to the initial start up, I could run 5 miles smoothly before it would starve and stall. Pump the bulb up and off I would to for another long haul. There was no rhyme or reason, or consistency as to air temp, water conditions or distance run. I too changed spin-on and engine fuel filters (engine filter looked like new, didnt even have any fuel discoloration to the plastic), changed the fuel line / bulb assembly and connections with OEM parts, checked all the engine hoses and small fittings too. The fuel line / bulb assembly was an aftermarket replacement done 7 years ago. That particular hose had the clear plastic liner which was starting to detach from the hose interior which would / could cause a partial blockage or flow reduction. After replacing it, the boat ran a bit better but still had the random fuel starving / stall issue. Once I replaced the loose fuel pump with a new OEM fuel pump and gasket, the problem went away. Have you checked that the fuel pump is tight? My fuel pump was the original 2002 one, so the diaphrams / valves may have been starting to deteriorate some. I dont know if it was the pump itself, or it having worked loose a bit, but the engine runs like new now. All your symptoms are pretty much what I’ve been going through. Now it might happen only once in a day, or twice. I actually found my original fuel pump loose when I was replacing the pump and gasket. Everything was replaced with OEM parts. I’ve rebuilt the carbs, even thoroughly inspected for carb body cracks, loose inlet tubes, etc. With my ocd it’s driving me nuts.:) Thank you Quote Link to comment Share on other sites More sharing options...
stinkbait Posted February 9, 2023 Report Share Posted February 9, 2023 I've had a similar issue with my Yamaha 115 2 stroke. Replaced the fuel water separator, fuel strainer, and fuel pump/gasket. The problem still happens occasionally but not as often now. Seems to only happen on the hole shot if I've been fishing a spot for a long time with the outboard off or if I had to tilt the outboard up. A couple of pumps to the primer bulb is all it takes to get it going, so I probably need to swap that out next. Maybe I need to crank the new fuel pump down a little tighter too? Quote Link to comment Share on other sites More sharing options...
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