Engine won't start again after first fire of the season

[beruken]

I started my boat for the first time to flush the antifreeze and see how it was running. Put new plugs and fuel filter on. Fired right up and I let it run for a while to juice up the battery. After a few minutes it stalled and it has been 2 weeks now still no luck starting it. Does not sputter, nothing.

1999 mercruiser 4.3l mcm thunderbolt ignition.
sn 0L209920

I ran thru what I could of the troubleshooting guide with exception of spark gap test and are going to do a check on the tach wires as posted in other topics. Here is what I found.

Fuel is entering carb
Spark test with spark plug off. Looked ok. .I'm not sure if it was weak.
Checked voltage at coil. 12v
Checked voltage from red/wht of ICM ~10v seemed a little weak.
Cleaned corrosion from all distributor components - not yet replaced. and checked ignition sensor switch for cracks
Oil is clean and new.

I know there have been some similar issues posted but this engine was purring before it just stalled. Anything else I can look for?

Ken

 

[Fun Times]

Fuel is entering carb

Is this you have fuel getting to carburetors inlet fitting (IE fuel pump pumping)? now do you see fuel being delivered to the engine from the carb when you pump the throttle while the flame arrestor is removed?

Try pouring just a little bit of fuel down the carb and see if it will try to start at all. Maybe you have a stuck needle and seat inside the carb not allowing fuel to flow.

 

[beruken]

Yes, I checked the fuel pump by removing it from the carb as well as viewed it entering the manifold with the flame arrestor off. Sorry that was another test I did not note. I also tried using starting fluid and replacing some of the old plugs to see if it even sputtered.

When I checked the spark with the plug off, I also put my thumb over the hole to see if there was compression and no mechanical failure. So I have to assume the crank and timing are intact, correct?

I checked with Autozone what the issue might be and they had mentioned something about a module (I think they were referring to the ICM) heating up for the first time and failing. I'm going to check back with them today as they mentioned they could test it. I don't think they are prepared for a Mercruiser ICM though.

Thanks for your response Fun Times.

 

[keith2k455]

How's your fuel filter? It stalling makes me think something clogged. Another question. ..is your choke closed when you try to start it?

 

[alldodge]

Here is the TB-4 troubleshooting guide

 

[achris]

As you have a Thunderbolt V ignition system, you are going to need this one. (almost the same, but not ) Also, that serial number you provided is for the transom assembly, not the engine... Cheers...

 

[alldodge]

Also, that serial number you provided is for the transom assembly, not the engine

Guess I missed that one, used his serial number range to look it up at mercruiserparts and it was a TB4, guess I should use merc and look it up there first to verify. Thanks for the catch

 

[beruken]

Hey Guys, thanks for the input. The serial number is from the flame/spark arrestor cover plate on my engine. I did buy a new coil, dist cap and sensor switch but have been busy dealing with another issue as one of the starter bolts loosened and snapped the other. I've got bigger issue's to deal with and that ain't going well.

 

[beruken]

So if anyone is still monitoring this I have the starter issue fixed and have installed the new ignition components, sensor, cap rotor and coil still no luck. I am measuring 24 volts at ignition module. Not sure how this got doubled it was 11.9 a couple weeks ago. I'm pretty sure the module is bad but are reluctant to spend 500 bucks without absolute certainty. I'm a little uneasy with grounding the coil and green/wht from module. BTW the engine serial number is OL349983

 

[Bondo]

I am measuring 24 volts at ignition module.

Ayuh,..... Does yer boat have 2 batteries,..?? I think somewhere, they're shorted together, in series,...

 

[beruken]

No I don't have two batteries.Starter wiring? I double checked when I reinstalled it.

 

[alldodge]

Measuring 24V tells me you either have a bad ground (on the engine or where your negative probe is) or a bad meter.

 

[beruken]

Just wanted to close out this post for others who look at it. The problem has been rectified. Although I had installed a new sensor switch and coil, the boat still would not start. After checking the voltage of the battery under load, I decided to try jumping starting the engine. Still would not start or sputter . I learned the 3rd wire on the new sensor was a ground. Original sensor did not have this. Boat fired right up.

I think the issue was the battery. It would sound like it was cranking over quite well but in reality providing little energy to the electrical system. I have never seen this happen and could not understand why the battery never went dead after weeks of trying to start the boat.