2006 Yamaha 115hp 4 stroke

Hi guys, need some help, I have a 2006 115hp 4 stroke with around 900 hours, I have had a couple of Yamaha mechanics look at it but still can not find the problem, ok, doesn't do it every time but a fair bit of the time, won't start in neutral till you put a few revs on, then will start but pull back into reverse and stalls, if you do get it going for a while, just every now and then when you pull back into neutral will stall then same it needs a few revs to start, have put a new throttle position sensor on and an Idle air control valve, nether have fixed problem, also it has a knock in the motor sort of like a big end knock, the mechanic know thinks it could be the striker plate? Just don't want to keep throwing money at parts if it doesn't fix the problem, any suggestions? Thanks in advance

And what / where is the " striker plate " on this engine.

From what the Yamaha guy said it is under the fly wheel, trigger plate I think actually not striker, cheers

Both the mechanics I have had look at it are Yamaha mechanics, both said trigger plate, also known as pulser coil they said

Put a few revs on means, push the button in the middle of binnacle, this allows the motor to be revved but not in gear! So what I mean is push that button, move the binnacle forward to put revs on motor then it will start, hope that's clear??

OK, I think that we may be on the same page now.

I am surprised to hear of a Yamaha mechanic refer to a pulser coil as a striker plate or trigger plate. What country are you in? Here in the US a Yam mechanic would all but never use that term.

I doubt that it is a pulser coil issue. They all but never fail. And when they do it is more likely to be a hard failure. Not intermittent. Don't think it would make the motor stall or be hard to start.

As you know, it is not normal to have to advance the throttle to get the motor started. The idle air control valve should be the one allowing more or less air to the motor to facilitate a start. Since the problem is intermittent, and the motor has some age and time on it, I would start by carefully inspecting the wiring. Specifically, the wiring from the ECU to the idle air control valve. The connection of the wires to the terminals. The condition of the pins and sockets.

If YDIS is available, the laptop computer with Yamaha software can be used to activate the IAC valve. I would do the IAC valve test while jiggling wires around to see if maybe the IAC valve is not functioning due to a wire issue.