sport jet 90 backfiring not starting

[boatproblem]

I have compression tested this motor it has 135 to 140 psi on all cylinders.
the boat has good spark. what happens is when you turn it over it backfires really loud. and yes kicked the ride plate off.
now i have replaced the trigger and flywheel and the timing rod. and timed it per factory specs. i am at such a loss here, even on carb cleaner it will still not wanna start. i have also had it running in this config for a few seconds. but would it would idle up and backfire and die
thanks
jeff

 

[JB]

Re: sport jet 90 backfiring not starting

If your flywheel is correctly timed and the key is okay it sounds to me like mixed plug wires.

To get a loud backfire from the exhaust at least one cylinder is getting spark with the exhaust ports open. Most common cause is sheared flywheel key, second is swapped plug wires.

Less likely is crosstalk among triggers for the different cylinders.

Good luck.

 

[boatproblem]

Re: sport jet 90 backfiring not starting

We took the boat out today, and this is what we found. We removed the flywheel again, and looked at the old trigger and compared it with the new one. The wire colors are the same colors, but located in a different configuration with the old one. We attempted to at least connect the wired to the corresponding side of the trigger and we started it and, it fired and idled. Got excited and went to the lake. The boat will fire and idle in the water. But any throttle at all and it would die. We did not bring the timing light with us, but played with the timing and retarded it as far as it could go and showed no change. We checked the coil wires with the wiring diagram and they are hooked up correctly as 1-2-3. My main question now lies in the trigger, with the wires in different locations. Does it matter for the wires to be the same top and bottom (looking down on the trigger) as to left to right on the trigger, or is it only left side right side, needs to be color coordinated? I am going to check timing again, and I read that someone had marked TDC marks on the flywheel for all the 3 cylinders. and checked timing on all the 3. So that is my next step as of now. Also when the boat was in the water it sometimes would fire backwards, which tell me timing. Thanks for you time.

 

[boatproblem]

Re: sport jet 90 backfiring not starting

timing check update. After matching the wires exactly to the old trigger, the brown wire and the white wire were reverse on the new trigger. set the tdc on all 3 cylinders. coil #3 is timed with cylinder number one. coil #2 was not in time, but close to cylinder number 2, and coil #1 was timed in between cylinder 2 and 3. I am lost as to what to do. I honestly believe my problems lie in the wiring of this trigger. Can anyone supply a diagram as to what each color wire is supposed to do?

 

[boatproblem]

Re: sport jet 90 backfiring not starting

problem solved it was the trigger. havent figured if it is defective or wrong quite yet. but I ran the boat today with the old trigger glued back together, and it ran great.