Mercruiser 4.3L won't start

Tamas1975

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Nov 15, 2024
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Hi all, Bought my first boat and my 4.3 won't start. It turns, got a new ignition coil, new distributor cap, new fuel but she won't fire up. There are 2 cabels that are extra and not attached. Any help is very appreciated. Thanks
 

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Bt Doctur

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if those number are correct ,there on completely wrong
#1 #3 #5 all the way up front ,right (port) side of motor
#2 #4 #6 all the way up front starboard side
firing order clockwise 1,6,5,4,3,2
This is assuming nobody fugged up installing the dist at some point
The ign wiring is a purple and a grey from the module on the elbow goes to the + of the coil and the - of the coil,
coming out of the module is a White/red and White/green they go to the rear of the dist, white/red on the left stud, white/green in the right stud,
the white/green stripe in the pic is from the shift interupter switch that goes with the White/green at the dist.
 
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Tamas1975

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Yes, those numbers are wrong, but the order is correct, just checked again. Got the purple and gray to the coil and the 3 cables to the distributor.
 

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Tamas1975

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Took the distributor off. The finger does turn. I can't attach any wires at the distributor, since it's direct wired. I can't measure any voltage at the coil with ignition on. Is that normal?
 

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alldodge

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The distributor doesn't look factory, what brand is it?

What is the motor serial number?

Took the distributor off. The figer does turn. I can't attach at the distributor, since it's direct wired.
Does the finger mean the rotor?
Explain can't attach distributor?

I can't measure any voltage at the coil with ignition on. Is that normal?
No, not normal
See if you have 12V on the purple wire with the key ON
 

Tamas1975

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The distributor came with the boat, not sure what brand it is. Should still have the old one too though. Motor sn 8289732. Yes rotor, not finger. The wires are directly mounted without any screws and connected to the module wires a bit further down. Yes I have 12V at the purple and also the gray wire. Cleaned the module pins (had light corrosion), but it didn't help either.
 
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Scott06

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The distributor came with the boat, not sure what brand it is. Should still have the old one too though. Motor sn 8289732. Yes rotor, not finger. The wires are directly mounted without any screws and connected to the module wires a bit further down. Yes I have 12V at the purple and also the gray wire. Cleaned the module pins (had light corrosion), but it didn't help either.
That looks like a stock mercruiser thunderbolt distributor. Are you getting spark if not go through the TB troubleshooting guide in the stickies
 

alldodge

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Not able to find that serial number, thinking it's maybe a 1985 model or there about, MCM 205, points distributor

If the boat has a Tach, remove the wire from it.
Could be the negative side of the coil might have 2 gray wires (one for Tach and one for distributor)
 

Tamas1975

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Yes, I do have a tach. Let me see if I can separate the grey wires. Here is a pic of the block number
 

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alldodge

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Appreciate getting the pic, but that's a casting number. The motor serial number will be on a aluminum tag above the starter riveted to the block
 

Tamas1975

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It is 1990 boat, if that helps.
The tach spins 360 degrees when I am trying to start it.
 

nola mike

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Not able to find that serial number, thinking it's maybe a 1985 model or there about, MCM 205, points distributor

Def a TB distributor...
Op, I assume you verified no spark? I didn't see it mentioned. Also would check all of your connections, that engine looks even rustier than mine.
 

Lou C

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That’s the part # of the intake manifold. Merc puts a plate above the starter
 

Tamas1975

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Def a TB distributor... Op, I assume you verified no spark? I didn't see it mentioned. Also would check all of your connections, that engine looks even rustier than mine.
 

Tamas1975

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Yes I did check for spark, but didn't see with my tool. I will do a wire check today and see what is hooked up wrong.
 

Tamas1975

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Is this the correct firing order? I have seen it the other way around...
 

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alldodge

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Scratch that, might just be correct

V6 firing order.gif
 
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Tamas1975

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I went through the troubleshooting and I do have spark, so I think it's my ignition sensor or my timing is way off...
 

alldodge

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If timing was off and you have gas then there should be some kind of backfire

How old is the gas
 
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