2000 Yamaha 115 4 stroke with 375 hours. Meticulously maintained and always ethanol free. I replaced VST, high pressure fuel pump and injectors 4 years ago (~150 hours, boat sat awhile it’s early years). Fuel filters and normal maintenance done yearly. I am having a weird issue that started the end of last season. It would sputter and pumping the bulb seemed to fix it temporarily. I just replaced the anti siphon valve and bulb and now pumping the bulb when the issue occurs does nothing. It did however seem to stay firmer, I do believe the valve was bad. I noticed that if I was ever below 2000 rpm, it would stall or sputter really bad. Any ideas?
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Yamaha 115 4 stroke sputter/stalling. Help!
- Thread starter Markdelz76
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Not easily. If it has never been replaced, it probably is time...I’ll check that out. Any way to test?
I see there is only one for your motor part number 6E5-24410-10-00
If you have access to a fuel pressure tester, the first step would be to test the pressure at the VST output. If the low pressure pump is bad, the VST will get starved for fuel and the high pressure out put will be low.
I don't have a manual handy to see what the pressure should be.
Also check that the inline gas filter (clear bowl) is not mucked up and that the bowl is seated correctly.
If there is a starvation issue, the problem is usually more pronounce at speed and load and yours isn't. Poor gas flow at low speeds that gets better at higher revs does point to the low pressure pump.
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I strongly recommend that you get a genuine Yamaha pump. There are some garbage pumps on the aftermarket world. The Yami pump is not that expensive, $50 maybe?Awesome. Thanks for your help! Have you had any luck with aftermarket pumps?
You may see that there are rebuild kits. Don't be tempted.
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My pump is like $250 because I have a 4 stroke. Stinks hahaI strongly recommend that you get a genuine Yamaha pump. There are some garbage pumps on the aftermarket world. The Yami pump is not that expensive, $50 maybe?
You may see that there are rebuild kits. Don't be tempted.
My bad.I did look up 2 stroke..
In this case, ignore my comments. I would definitely measure fuel pressure output at the VST first as well as checking filters and the like.
Are you able to squeeze the primer bulb (motor not running) until it gets firm?
When the motor acts up does the primer bulb collapse?
If you can see the level of gas in the clear filter bowl on the motor (cowling off), is the bowl complete full, empty, 3/4s full?
It is possible that the issue is not fuel but rather spark but that is a pure guess. To test that you need a spark tester gizmo. It is also possible to run the engine at a little speed in neutral and unplug the spark plug wires one at a time to see if the motor slows down. It should. Test all cylinders one at a time. Use a pliers with insulated handles and wear gloves when pulling the ignition wires. You can get easily zapped!
In this case, ignore my comments. I would definitely measure fuel pressure output at the VST first as well as checking filters and the like.
Are you able to squeeze the primer bulb (motor not running) until it gets firm?
When the motor acts up does the primer bulb collapse?
If you can see the level of gas in the clear filter bowl on the motor (cowling off), is the bowl complete full, empty, 3/4s full?
It is possible that the issue is not fuel but rather spark but that is a pure guess. To test that you need a spark tester gizmo. It is also possible to run the engine at a little speed in neutral and unplug the spark plug wires one at a time to see if the motor slows down. It should. Test all cylinders one at a time. Use a pliers with insulated handles and wear gloves when pulling the ignition wires. You can get easily zapped!
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Yep printer bulb is firm and did not help the issue when it was bogging down. I replaced plugs last year but will check them for sure. I did replace the coil packs 200 hours ago so they are new. The filters are all full. I start with plugs and then test pressure and confirm I am at 40psi at the rail and 10 psi after the low pressure pump.My bad.I did look up 2 stroke..
In this case, ignore my comments. I would definitely measure fuel pressure output at the VST first as well as checking filters and the like.
Are you able to squeeze the primer bulb (motor not running) until it gets firm?
When the motor acts up does the primer bulb collapse?
If you can see the level of gas in the clear filter bowl on the motor (cowling off), is the bowl complete full, empty, 3/4s full?
It is possible that the issue is not fuel but rather spark but that is a pure guess. To test that you need a spark tester gizmo. It is also possible to run the engine at a little speed in neutral and unplug the spark plug wires one at a time to see if the motor slows down. It should. Test all cylinders one at a time. Use a pliers with insulated handles and wear gloves when pulling the ignition wires. You can get easily zapped!
Ugh these issues are annoying. I appreciate your help.
Good plan. One comment though; The clear bowl on the gas filter (motor mounted) should not be full. If it is, you may have an air leak somewhere. It is normally almost full.
Not seating the plastic bowl correctly is a common issue especial since the bowl rims tend to distort out of round.
The reference I made to the spark was to unplug each cylinder one at a time and confirm that the motor slows down or acts rough. At this point you do not need to pull plugs, just plug wires or use a spark tester ( cheap at Harbor freight)
Not seating the plastic bowl correctly is a common issue especial since the bowl rims tend to distort out of round.
The reference I made to the spark was to unplug each cylinder one at a time and confirm that the motor slows down or acts rough. At this point you do not need to pull plugs, just plug wires or use a spark tester ( cheap at Harbor freight)