ignition help

i have a 2007 bayliner with a 4.3l carburated .last summer it ran fine with no issues for me .i bought the boat early summer last year the previous owner said he had problems with it .he said after it got warmed up running for 30-40 minutes and you shut it off it would not restart until it sat for a few hours normally over night. since Ive had it it ran great parked it for the winter and pulled it out in February and when i was coming out of the no wake zone it stumbled .it gave me problems all weekend shutting off and not restarting stumbling basically running like crap to the point where it would not start and had to be towed back to loading ramp.since having it home i have replaced plugs,wires,cap rotor which all were in bad shape .i also replaced fuel filter and checked for water and it was clean .pulled all the fuel out of tank and refilled with fresh fuel,let it run all fuel out of carb then hooked line back up to fuel pump and fired it up.it ran good for a while then started having trouble idling then it started stumbling again badly and if you accelerate slowly it would stumble and pop through the carb and rev up.the last thing it did was it just sounded different when it started acting up it sounded like someone pulled the timing out of it.im at a loss and don't know what else to do also had the coil checked and they said it was fine

ignition is a alpha part number 861251-1
4.3 lh alpha

Re: ignition help

Have you checked the timing? Fuel pressure?Distributor loose? Carb been apart,rebuilt,cleaned? Could be a number of things

Re: ignition help

pulled top off carb it was spotless ,dist. is tight ,i cant find the timing tab to check timing .im trying to find out if it might be the icm

Re: ignition help

See if the ignition module gets really hot when the motor is running. I have heard of Thunderbolt IV's suffering a kind of thermal breakdown when they get hot. I know you have the later ignition, but I believe they are related. That part is kind of spendy though so rule out everything else first. Does your ignition have the sensor under the rotor? Might be that. Is your fuel line close to the (hot) motor? If so you could be getting vapor lock. How are the fuel filters, change em if they have not been done recently. Pour out the contest of the water separating filter into a glass jar and see if it separates out any water.
Also, is all the new stuff in there correctly?
There are tests for the ignition pieces, do you have the manual?

Re: ignition help

yes it has the sensor under the rotor that's the only thing i haven't replaced .the fuel filter is new i poured the old one out and the fuel was clean no water .i even drained the fuel tank and put in fresh fuel just in case.the fuel was a light yellow color.i just found a brand new ignition control module for 145.00 on eBay i went ahead and bought just in case that was to cheap to pass up with it still in the mercruiser package. not sure what they call the sensor in the distributor so i can look it up

Re: ignition help

My vote's on the ignition module in the dissy. I've seen a few of them go, and symptoms fit.

Chris......

Re: ignition help

ok i just replaced the ignition moduke with a brand new one.thought it was better at first but then it started hesitating again .dont know what to do at this point