Mercruiser 4.3 LX boat died while driving and won't start back up

[Scrowley707]

Hi folks I am new to I/O but have mostly had wakeboard ski boats. So I just bought this 1996 18.2 Regal with a 4.3 LX alpha gen + outdrive. I took it out for the first time and it was running very smooth for an hour then I felt it loose power for a second. I slowed down and everything felt ok so I started to go again and when I got to 75% it just died and wouldn't start back up again. The coil tests good. I unplugged the tach. I bypassed the shift interrupter. I went through the 5 step ignition test that. I do dot get spark from the green white wire from the distributor when I put a spark gap tester between the coil and ground. Does this mean I need to change the ignition module? My ignition module is 807829-1. I took it off inspected it. It looks good put it back in and same result.

 

[dingdongs]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

sensor needs to be replaced if your dabbing the green/white wire to earth & not getting spark.Under the cap.
The module does the advancing.

 

[achris]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

Do you have Thunderbolt IV or V?

 

[Scrowley707]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

I don't know how to tell if I have thunserbolt IV or V, I have attached an imge of the back of the distributor showing the ignition control module numbers, (I unplugged it to inspect the plug) I did notice that my sensor has been discontinued and replaced with a different part number and it looks a little bit diffrent so I ordered one of those suggested by "dingdongs" but according to the test I was running I thought if you did not get spark while running test from coil to spark gap test tool to ground and swiping the white/green wire to ground then the sensor was ok?

 

[achris]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

That's a Thunderbolt V system, so you need to follow the TB-V troubleshooting chart. Which manual are you using?

BTW, engine (or drive if we're working on the drive) serial number is King here. All information related to the engine can be found with just the serial number, so please post that whenever you have any questions.... (saves us having to ask a lot of questions you might not know the answer to )

 

[Don S]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

Here is the basic troubleshooting chart for the TB5, this should get you to the cause of the problem.

 

[Scrowley707]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

Here are the numbers on the top of the intake manifold. Are they the serial numbers you are looking for? GM12552422
I also went through the TB5 chart from Don S. and I got to problem 5A. Which I mentioned in my previous post I had already ordered. When I have it installed I will let you know how it goes. Thanks for all the good advice.

 

[achris]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

No, that's the GM casting number of the intake. The Merc engine serial number is either on the engine cover (the plastic one on top of the carb) or on a metal tag on the engine block, just above the starter motor... It will start with a '0', have one letter, then 6 digits... (see my signature for an example)...

Chris......

 

[dubs283]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

according to the test I was running I thought if you did not get spark while running test from coil to spark gap test tool to ground and swiping the white/green wire to ground then the sensor was ok?

does not necessarily mean the sensor is okay but there IS an issue with either the coil or the module

9 times out of 10 a no spark issue on a thunderbolt system is a bad sensor - but the modules do fail from time to time, coils as well but they are pretty bulletproof

 

[Scrowley707]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

Serial Number is FS21961 it was located above the starter.

I also received the new sensor and installed it and still no spark

 

[achris]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

Here are the numbers on the top of the intake manifold. Are they the serial numbers you are looking for? GM12552422
I also went through the TB5 chart from Don S. and I got to problem 5A. Which I mentioned in my previous post I had already ordered. When I have it installed I will let you know how it goes. Thanks for all the good advice.

Serial Number is FS21961 it was located above the starter.

I also received the new sensor and installed it and still no spark

So you did get spark with the test of the white/green against ground... If you did, and you still have no spark with the new sensor, check that everything is grounded correctly, including the dissy body...

BTW, your number is incorrect. Like I said, one letter, 6 digits...

Chris....

 

[Scrowley707]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

Sorry my serial number is F821961 the 8 looks like an S.

Chris thanks for the help. I did not get spark the first time because I did not know you were supposed to rapidly swipe the green/white wire against ground. When I did this I got spark. That is what lead me to problem 5A. I did not try it with the new sensor yet. Should I try it again with that one?

 

[achris]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

Yes, try it with the new sensor... of course. Run through the chart from the beginning again, and have you checked those grounds?

 

[Scrowley707]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

There are 2 small black wires coming from the harness that I have grounded on the ignition module bolt. The new sensor has a large black ground wire included it it that I grounded. (The old sensor did not have a ground). The dissy body is that the distributor? I searched for it and can't figure it out. I will test it again and let you know.

 

[achris]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

'Dissy' is short for distributor, yes...

 

[dubs283]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

The new sensor has a large black ground wire included it it that I grounded. (The old sensor did not have a ground).

best to connect the ground wire on the new sensor to the same ground stud on the engine as the battery

the old sensor grounded either through the distributor housing or there should have been a small wire from one of the mounting screws going to a ground

 

[Scrowley707]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

I checked the dissy body. If its ok to put the volt meter to the pos of the battery and the black ground on the dissy body and I checked it against the rotor area also. I moved the ground of the new sensor to the back of the engine where the battery grounds. I also changed the ignition coil. And still no spark. Any more ideas?

 

[Scrowley707]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

Ok actually it just started all hooked up normally. I am not sure what it was. The ground, sensor, or the coil. I will take it out for a ride tomorrow and let you guys know how it goes

 

[Scrowley707]

Re: Mercruiser 4.3 LX boat died while driving and won't start back up

I took it out yesterday for a couple hours and everything seemed to be working fine,
thanks for the advise guys,

 

[Scrowley707]

This is my old post I don't know if I can post in here again but I am having problems. I went to take my boat out again this summer for the first time and I only get spark for a couple seconds and then it quits. I started a new post and it was erased. Cause of the server error I think. I have already replaced the cap, rotor, wires, sensor. And that is it. I have 4 volts coming from the ignition module to distributor on the red/white wire and I believe I need 12v? Does that mean the module is bad?