HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

daddy1983

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just want to add this was a brand new motor with maybe 10 hrs on it. Totally my fault, I'm an idiot, I KNOW. Took it out for its first run and noticed when i took the engine cover off I could hear trickling of water coming from what I assume is one of the bellows. Didn't have time to pull it out of the water before wife had to be to work so thought it would be fine overnight. I ran the bildge pump before I went to bed(not an auto bildge). Woke up to the 2/3rds of my boat under water. Immediately got to pulling it up. So far, drained the oil and refilled it, pulled plugs turned the motor over for about 10 minutes, drained fuel from carb (tryingto run it off a gas can). Can't get fire..... replaced coil(have 12 v a + terminal), distributor sensor( have 12v on red and white), and amplifier still no spark. Im losing my mind because I know time is of the escence. Any and all help is appreciated . thank you. Went though the ignition trouble shooting process with no luck. Only thing I dont quite understand is "inserting a spark gap" to tap green and white lead on ground. Does this mean just hold the wire a hair off the terminal?
 
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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

Hi, and sorry your first post is to report a sinking:(.
Was the engine totally submerged? Including the ignition components? If so, I suspect there is still water in there somewhere. Remove all ignition components and make sure they are dry ( use hair dryer). Check all connections.
What about the battery- are you using a new one?
 

daddy1983

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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

Hi, and sorry your first post is to report a sinking:(.
Was the engine totally submerged? Including the ignition components? If so, I suspect there is still water in there somewhere. Remove all ignition components and make sure they are dry ( use hair dryer). Check all connections.
What about the battery- are you using a new one?


thanks for the reply. yes the whole ignition system was under water. Got a hair up my tail to go through the trouble shooting process again. There are 2 white and green wires going to one terminal on the distributor module, on my testing earlier i only tried touching one to ground with no spark. just tried the other one and I'm getting flash which by the trouble shooting process would mean my distributor ignition module is bad. I've since tried 3 separate ones from a boat junk yard(used) with the same outcome. Could all 3 really be bad? should I have to change my cap and rotor? They still look new(no corosion). Everything is dry. I'm still using the battery that went down with it because it seems to be fine. Holds a charge and everything.
 
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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

I'm surprised the battery is still ok! Check the voltage at the terminals - it should be 12.6 or higher If it's lower then try a different battery. I'm thinking if the battery isn't at 100% there's not enough juice to crank and spark at the same time?
Unlikely to have 3 faulty modules. Rotor and cap should be ok as long as they are dry.
I still think you should dry everything out with a hair dryer- it only takes a little water in the wrong place to stop the spark.

Here's a link to an older thread that contains a trouble shooting chart for the Thunderbolt IV.

http://forums.iboats.com/mercruiser.../88-mercruiser-4-3-litre-no-spark-414368.html
 

daddy1983

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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

I'm surprised the battery is still ok! Check the voltage at the terminals - it should be 12.6 or higher If it's lower then try a different battery. I'm thinking if the battery isn't at 100% there's not enough juice to crank and spark at the same time?
Unlikely to have 3 faulty modules. Rotor and cap should be ok as long as they are dry.
I still think you should dry everything out with a hair dryer- it only takes a little water in the wrong place to stop the spark.

Here's a link to an older thread that contains a trouble shooting chart for the Thunderbolt IV.

http://forums.iboats.com/mercruiser.../88-mercruiser-4-3-litre-no-spark-414368.html

quick question..does your distributor have a ground coming off of it anywhere? I can't seem to find one on mine but there is a ground wire with a ring on it that looks like it went to the distributor but cant find anywhere for it to go
 

daddy1983

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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

I'm surprised the battery is still ok! Check the voltage at the terminals - it should be 12.6 or higher If it's lower then try a different battery. I'm thinking if the battery isn't at 100% there's not enough juice to crank and spark at the same time?
Unlikely to have 3 faulty modules. Rotor and cap should be ok as long as they are dry.
I still think you should dry everything out with a hair dryer- it only takes a little water in the wrong place to stop the spark.

Here's a link to an older thread that contains a trouble shooting chart for the Thunderbolt IV.

http://forums.iboats.com/mercruiser.../88-mercruiser-4-3-litre-no-spark-414368.html

quick question..does your distributor have a ground coming off of it anywhere? I can't seem to find one on mine but there is a ground wire with a ring on it that looks like it went to the distributor but cant find anywhere for it to go
 
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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

quick question..does your distributor have a ground coming off of it anywhere? I can't seem to find one on mine but there is a ground wire with a ring on it that looks like it went to the distributor but cant find anywhere for it to go


My boat is in winter storage and I can't say for sure if/where the ground wire goes. My understanding is that most Merc distributors have a groundwire attached to the housing.

Can anybody else following this answer this question?
 
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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

Just had another idea. Was the shift cutout (interrupt) switch under water? If it was it may be shorted out? This would ground the primary side of the coil resulting in no-start.
 

EddiePetty

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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

Just had another idea. Was the shift cutout (interrupt) switch under water? If it was it may be shorted out? This would ground the primary side of the coil resulting in no-start.

......likewise if the kill switch (lanyard) got wet.....
 

daddy1983

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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

Just had another idea. Was the shift cutout (interrupt) switch under water? If it was it may be shorted out? This would ground the primary side of the coil resulting in no-start.

it was under water but it wont turn over if its in gear but will if its in neutral. wouldnt that mean its fine, or could it still be shorted out? is there a way to bypass it?
 
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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

The switch only affects the primary side of the coil, the starter will still crank. The switch is usually in the "open" position - if it is shorted out it will be in the "closed" position which grounds the circuit. Disconnecting one of the wires on the switch will effectively bypass it.
 

daddy1983

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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

The switch only affects the primary side of the coil, the starter will still crank. The switch is usually in the "open" position - if it is shorted out it will be in the "closed" position which grounds the circuit. Disconnecting one of the wires on the switch will effectively bypass it.

you my friend are a LIFESAVER!!! she's purring like a kittin thats never been drowned. Thank you sooooooooo much. If there is ever anything I can help you with please don't hesitate to ask. Thanks again. Really.
 
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Re: HELP HELP PLEASE!!! 1990 merc 4.3L with thunderbolt iv ignition sunk

you my friend are a LIFESAVER!!! she's purring like a kittin thats never been drowned. Thank you sooooooooo much. If there is ever anything I can help you with please don't hesitate to ask. Thanks again. Really.

I'm happy you're floating and running again:). Bon Voyage.


PS. Remember to dry/change that switch.
 
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