Sportjet 90 misfire

[Teeko]

Hey all, new to this forum and to jet boating. I've got a 1995 thundercraft typhoon with a remanufactured engine dates dec, 05. Boat starts and idles great but misfires for the first few minutes. Will barely creep up over idle. Eventually (5-20 minutes later) it clears itself out and seems to run strong. Plugs look brand new, cleaned them anyway. Carbs looked clean but again, cleaned the jets anyway. New fuel filter/water separator. I've read some stuff on here about ignition components being faulty but just want to see if anyone has had a similar experience and what the cause was.

 

[tdonoughue]

Welcome!

I know nothing about the Typhoon. There is your disclaimer.

Unrelated to the misfire, I would check and probably replace the thermostat. Sounds like the engine is taking forever to warm up...

Then, the misfires, I would start with new plugs. I know you cleaned them, but a fresh plug can do wonders. Then, yes, I think you are looking at your ignition system to make sure you are getting good, consistent spark. Could be a bad wire or a bad coil...