115hp Optimax Stalling Issue

[zack123]

Hi, I've tried to do some reading up on this but I can't seem to find anything that matches the problem I am facing so hoping someone can help me out.
Engine starts fine, and will sit at idle fine also, bring it up to 3000rpm, it starts to struggle a bit with some hesitation but up to 4000 and above it seems to do just fine.
The problem starts when I bring it down to neutral real quick, it'll splutter a little and then stop, restarting again no issues, and seems like if I bring it down slowly it's ok, but anything down pass 1000, it'll start to splutter again and stop.

The problem started a few weeks back and the engine would just stop by itself at idle after about 5-10seconds, ended up limping back home doing 10knots from about 10miles out, I had to push the lever all the way down to get it to this speed. Ran it back home and was running really rough, found out the plugs were fouled real bad. Replaced them and sounded good again, but this problem of it turning off at idle after about 5-10seconds still happened. Serviced the low pressure pump, replaced the fuel filter and it seems like the problems even worse as described above where coming down from high revs quickly would cause it to splutter and then turn off.

2007 Optimax 115hp
Serial: 1B519455
Hoping someone can help me out as to where to look first, any assistance is appreciated.
thanks for your time,
Zack

[JOE54]

need to test fuel and air psi , possible leaking

[zack123]

Just an update, I've found the issue to be the diaphragm in the air pressure regulator, there was a slight tear in it. Now doing some reading up, this little thing seems to be very controversial, mainly the cost of it. Can someone tell me the part number for this diaphragm?

Just another question, can anyone tell me if the 115hp have a tracker valve? I see this coming up some of the threads that I have come across multiple forums and even looking at my service manual, there is no mention of the tracker valve. The only valves I can see on the rail (there is only 1 rail, I assume the bigger Opti's have 2?) is fuel pressure regulator and the air pressure regulator.

thanks

[JOE54]

8m6002988,no tracker on 3cyls

[zack123]

thanks Joe!

[JOE54]

yes sir