Yamaha T8 issues seems to be spark related?

[skpcoastal]

Yamaha T8 had run good all day. Shut of raised the motor and saw fish on the finder so dropped it back down and started it. Idles fine but if you give it gas it would cough and backfire. Could mess with it and get it to go full throttle but only for a short time

Pulled plugs they were black.
Main motor is plumed of the same fuel filter. It runs fine.
Replaced plugs no change.
Removed plug wire one at a time at idle both have spark as motor changes struggles if one is removed.
Read multiple threads somewhat similar pointed to carb issues.
Removed carb cleaned high speed jet could not get low speed out as it stripped.
Now would not idle still could still not accelerate
As I messed up low speed jet I bought a reman carb for time issues vs getting low speed jet.
Installed new carb runs the same.
Pulling choke out does not make it better but worse.
pumping bulb does not help.

Seems to be something electrical on throttle advance?
Any Ideas?
Going to end up in the shop if I cant figure it out.
It is on the boat in the water and we have a few weeks here for coho salmon a year so any help to diagnosis would be appreciated.

Don't know if a shop manual would help on this.
If any one knows how to check the electrical on this I'd appreciate the help

thanks, SKPcoastal

[TownsendsFJR1300]

I'd check the fuel pump diaphram..

Sounds like it's leaking and flooding the engine with fuel..

[mitch184]

2nd vote for fuel pump diaphragm. Assuming the "black plugs" are fuel and not oil blowby

[skpcoastal]

Pulled the fuel pump out.
1/2 of the plastic housing that surrounds the plunger was broken off. I pulled the valve cover and could only find a 1/4 so there is a 1/4 somewhere in the motor or maybe fell out when i pulled the valve cover but I don'think so.
Do I need to worry about this? Any way to make sure oil passages ways are clear? How would you clean out if the plastic is in the motor. Change the oil?

Anyway replaced the fuel pump. No change.
If it start the motor at idle can not get to speed up it coughs sputters. If i start the motor with throttle it will run for a short time fast then cough and sputter. I can shut it off restart and it will do the same thing run fast then cough and sputter.

Only think I can think of is fuel. Would fuel starvation make it cough and sputter?

[99yam40]

maybe oil pressure is low or out of spec,and going into RPM reduction mode

or the motor is over heating and going into RPM reduction mode.
does this motor have lights or buzzer that should warn of this happening?
do you know if these things work as they should?