Backfiring?

[Fit to be Tige]

Hey guys. It has been a while! My 1999 Tige 2100i has always run perfectly, but since we moved overseas she has not put in the hours as normal. So we just took her out and all seemed great. Once she was warmed up we revved up, but the exhaust turned very black (rich fuel mixture). I slowed down and it corrected itself immediately. But then when accelerating again the same violent backfire. On the way back to the launch the alarm started going off at a five second rate.

It seems the alarm every 5 seconds is the transmission alarm? I checked the transmission oil and it was too dirty for my liking, so I changed the oil (twice) and took out transmission oil
cleaner and flushed it so it was clear. The alarm does not go off now. However, the backfire still occurs. It only happens when going at very high RPM, but then is so bad the engine almost stalls.

Any ideas? It works so well at lower speeds.

[NICKYPOO]

What motor? When was the last time you tuned it up? What fuel are you running?

[boatwakes]

Ignition sensor inside distributor. Mercruiser part number 87-8929510Q02 about $60. Sierra part number 18-5116-1 about $45. The new unit comes with potted circuits and an extra ground wire that needs to be bolted to the engine block but instructions come with them. Also, check the trans cooler located right next to the starter and back flush any crap out of it that may have clogged some of the cooling passages.

[NICKYPOO]

Along with my regular tune up this spring, I replaced the cap, rotor and sensor. It's been running like a stabbed rat.

[Fit to be Tige]

Great, thanks guys! Sounds like a fairly simple fix. I will get the part and give it a try. It may also be partly fuel since it hasn't been run much, although it does have fuel stabilizer in it, I probably need to run through that tank.