Thunderbolt IV ignition module

I have a 4.3l volvo penta motor with a Mercruiser thunderbolt IV ignition system. I had issues after running the boat for a hour and then sitting for a short period of time. When I start the boat up she runs fine then after 30 seconds she dies. She will fire right back up and run another 30 seconds and die. I have gone thru the intire fuel system and even made sure the fuel tank vent was clear. I have put in all new parts including the cap and rotor in the distributor.New plugs and wires and had the coil tested. The boat mechanic told me it is probably the ignition module acting up. He says that after the boat runs and gets up to temp 150 that the ignition module could be shorting out? The module on the system is part number 805361T1. Could this be the problem and how do you test the module on the boat. Boat is a 20' Wellcraft Nova with a 4.3l GM V6 and a Volvo SP drive 1992 No water in tank,fuel seporator filter or carb. Electric fuel pump check out fine,pressure and volts good. Fuel getting into carb fine cause it fires right up. Boat is only run in fresh water lakes at 500-2000ft elevation and outside temps in the 80-100 degree. Thanks!

amplifier or module in the dist. one or the other is breaking down.

The ignition module is external and bolted to a heat plate on the exh manifold. I replace the ignition sensor in the dist thinking it was that but still dies. It will start right back up each time after it dies. So it must be the ignition module then? Thanks,

not that i know more than anyone but i had the same problem in my boat,99 baja 305. crank, run appx 20- 30 seconds shut off,repeat ,repeat, finally after checking,replacing parts it was the oil pressure sending unit which cuts the fuel pump if no oil pressure is present. Possibly check that to from a novice mechanic.By the way take a gem clip and jump the 2 wires, hope I'm right lol

good call on the oil pressure switch!!

Thanks for the response! I had the boat checked out and from what the mechanic told me I don't have a oil pressure safty switch on this boat. My guage reads 70-80 psi for oil pressure. I wish it was that easy in the beginning. I thought from the beginning it was that or a fuel delivery issue. After lots of process of elimination I am stuck at this ignition module question. The cheapest I have found a new one is $263. bucks. I did not want to keep throwing $$$$ at it but..........

Chief, WHoooow there big dog!!!

First he has a 4.3 litre, that is a V6 not a V8

Second, Tyeefisher, do you have a electric fuel pump or a mechanical one.

If you have a electric fuel pump you HAVE to have a oil pressure switch. Coast guard reg.

Please spend some time and get more familar with you boat motor and get the specifics so we are not throwing out guesses that are NOT relavent!!!!!!!!!

CANT HELP IF YOU DONT TELL US AS MUCH AS POSSIBLE.................geeeezzzzeee!!!!!

He says that after the boat runs and gets up to temp 150 that the ignition module could be shorting out?

Click to expand...

Ayuh,... Pretty hard to believe it's getting to 150° in 30 seconds....

I also believe the fact that the fuelpump is improperly wired is the Problem...
As it'll take about that long to run the carb dry...

I have some more history for you. The boat was purchased new from a now defunct dealer in Eugene Oregon. He the dealer bought the hull out of Florida and put the motor in later. He put a 4.3 volvo penta motor and drive. He said at the time back in 1993 that the mercruiser thunderbolt ignition was the best. The boat has worked GREAT up intill this year. I do have a electric fuel pump in this boat that is brand new. The mechanic told me I do not have a oil pressure safty switch. Is it supposed to be on the engine block next/with the pressure sending unit or ? Like I said in the first post. The boat will start and run fine and I can go around the lake for 45 minutes with no issues. It is when I stop and sit for a period of time. The engine does not cool back down to zero temp it stays at 100-150 depending on how hot it is outside. The problem starts when I start it up to go again it starts right up with no issues then dies after 30 seconds. I can repeat this process of start die. I have all new ignition except the module and all new fuel system from the tank pick up to the carb. I will get a second opinion on the oil pressure safty switch myself but to me it does not look like anything other than the basic oil pressure sending unit with one wire on it. I also don't think the fuel pump wireing is a issue. It has a plug that plugs into it and it has worked with this plug for all these years. ALso why would it run for so long in the beginning. I really appriciate everyones comments and suggestions. Thanks, Jeff

WOW now you have clearly stated all of the issues, symptoms and components.

You should have done that the first time!!!

We are not mind readers nor can we see into the past or into your boat for that matter,

That bieng said,

If you only have ONE wire at the oil pressure sender than there is NO pressure switch there!

The fuel pump runs with the key in the "run" position.
When this happens (WONT STAY RUNNING) again you need to see if the pump is pumping, turn the key to the run position and listen for the wine of the pump. If that is good then turn the key off and remove the flame arrestor and actuate the throttle linkage while looking into the carb. If fuel is squirting into carb then we can assume you have fuel. If not then you now have a starting point.

The ingintion/timing controll module rarely causes a hot start/stall condition.
It "tpically" causes an above 2500 rpm missfire/backfire/bad running engine/loss of power. Again I say typically!!

The fact that it runs for a while and does restart says to me the ignition is good.

Also you should check where the fuel pump is wired into the harness, maybe something is questionable there.........and you should look into a pressure switch.

The purpose of the switch is to shut down the fuel pump incase of any saftey issue within the bildge area such as severe overheat/flames and the engine stalls but the key is left in the run position......The lack of oil pressure will KILL the pump. If it does not there is a chance of a ton of fuel leaking into the boat. Likely? maybe not but possible!!! Just so you know.......

I just got back from the shop and did the fuel pump test again. After doing the above and turning the key back off I had plenty of fuel pumping into the carb. I did three pumps and had fuel each time. I followed the wires from the pump into the main harness and all looked fine. I have no corrosion on any of the wires. This boat has always been in a insulated storage unit since new. I checked the back side pannel where all the guages are and did not see any loose wires or corrosion. I seen that there is a 40 amp circut mounted on the top left side of the motor. I pushed the red button and it seemed solid. Do these ever have issues? I have never had to reset it. Some more info, I also put a new coil in while at lake Shasta to see if I had a bad coil after the motor was at running temp. It was 100+ out on the lake while we were down there. The weekend prior to us going to Shasta I ran the boat at Lake Foster for the entire day and the temp was 65-70 out. The motor still ran at the 150 temp but inside the engine compartment I think it was mutch cooler than at Shasta. So this is why I am looking at a heat realated question. I also put a spacer between the carb and intake manifold thinking it was a vapor loc issue due to heat. I will get a oil pressure safty switch installed. I want to be safe !! Thanks All.

Why not take an inductive pickup timing light with you, do the 30 minute thing, and then start it up after hooking up the light. All you need the light for is to indicate spark. Keep the trigger queezed until the engine dies. note if the light continues to strobe as the engine dies. If it does, find the oil pressure switch that is installed and is causing all the problems.

when they fail, it is on the "inside" and from normal use. No climate controlled storage will help with this one. If it turns out to be the switch, but two and put the spare in your tool box. they have a bad habit of failing at the worst times.

I will do the timing light thing you are talking about but I still dont have the magical oil pressure switch you are talking about. Sorry but two marine shops can not find that I have this componet on my boat. I guess they are as stumped on this issue as me. The only part that is not new is the ignition module so I bought a new one. I guess if you see one on ebay for sale it was not the correct part, I thank everyone for all the input. I have worked on many cars in my life and have never come accross a issue that has stumped me like this. I am open for any more opinions,situations from people that have had the same story. I started with the basic process of elemination of fuel. Then went to the ignition system and replaced every component except the module. I purchased a new module just because I am tired of not having my boat operating during the summer season. I will let you know if that was the problem. I am still wanting to hear from anyone who has a opinon. I have always thought that the more people that express their opinion the smarter the results. Thank you ALL, Jeff Fish On!

If you happen to find out what the issue is, please let us know.. I am having a similar issue and in the process of eliminating issues. I have an 1983 228 mericrusier and it runs fine for a long period of time and then all of a sudden it starts to backfire and stahl, etc when giving it gas... Runs fine at low RPM... Someone suggested to replace the Fuel Filter in the Carb and I will not be able to do it until this weekend... Please let us know what you find out as the issue... Good Luck...

I'm new to this site, my father-in-law turned me onto it as I have what I now believe to be a ignition module issue.
My 1992 merc 4.3 litre v6 chevy engine has been giving me fits as I'll be driving for about 30
minutes at 3600-4000 rpm and then BANG! Nice backfire. Take it down to under 2200 and it seems ok. Now the boat has been tuned, plus a new carb per my "mechanics" instructions.
Now into this clown to tune of 1600 cabbages.
Going to take it to a certified merc guy and let him cruise around with it till he experiences same issue. will post again after I get this resolved Blu