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Ignition sesnor or ignition module?

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ussoldier_1984

Contributing Member
hey guys back to pick your brains lol. question is how do I tell if the ignition module or ignition sesnor is bad? boat is doing its stupid thing again where after about 20 mins when everything is warmed up the boat is hesitating back firing loosing power and running like crap hard starting stalling. how do you tell if its the igntion sesnor bad or the ignition module acting up. from the forums I have read they both can cause my symptoms. one is 300 bucks and the other is only 50.

Boat has freshly rebuilt carb new fuel pump fuel system completly checks out right down to the vent. new dist cap new rotor new ignition sensor in dist cap new plugs new wires new coil. (all mercuiser parts)

1995 maxum 1800SR mercruiser 4.3 lx vortec with thunderbolt IV ignition
 
I have followed the steps and it says to replace the ignition module. I dont have that kind of money to just replace it I want to make sure its deffintily whats wrong
 
ussoldier_1984 said:
hey guys back to pick your brains lol. question is how do I tell if the ignition module or ignition sesnor is bad? boat is doing its stupid thing again where after about 20 mins when everything is warmed up the boat is hesitating back firing loosing power and running like crap hard starting stalling. how do you tell if its the igntion sesnor bad or the ignition module acting up. from the forums I have read they both can cause my symptoms. one is 300 bucks and the other is only 50.

Boat has freshly rebuilt carb new fuel pump fuel system completly checks out right down to the vent. new dist cap new rotor new ignition sensor in dist cap new plugs new wires new coil. (all mercuiser parts)

1995 maxum 1800SR mercruiser 4.3 lx vortec with thunderbolt IV ignition
Click to expand...


300 is not expensive in the boating world. some of these modules go for 1200...

this is usually the module after engine warms up 15-20min.
 
Last edited:
Look on craigs list or ebay,

Just make sure you get a money back guarentee incase the one purchased is bad........It is a lot cheaper but it is also a gamble.........
 
If you are tired of EST and possible Module failure, you could eliminate the module and get away from EST ignition altogether with the Mallory Marine YLM700AV.
BTW, these are magnetic VR triggering........... not photo eye.
Just a thought!


maa-ylm700av_w.jpg
 
works real good did away with my thunderbolt lv i bought the kit wires,dist,coil, easy to install takes 15-20 mins if u know what ur doin. boat runs good!
 
ussoldier_1984 said:
  1. How does it do the advance?
  2. I believe that my ignition is supposed to have 14 degress of advance as the motor turns more rpms
Click to expand...
  1. It does so mechanically! No module that can potentially fail.
  2. Yes, if 14* is accurate, that is what the module adds to your BASE advance of XX*. The Mallory works in the same way, but mechanically.......... NO EST (electronic spark timing).
Mallory has been making these long before M/C came out with their version of EST.
If/when you do this, bring the crank around to # 1 TDC C/S before removing the TB distributor.
 
sweet im deffinitly going with the mallory. Few more questions. how does this one wire into the shift inturrupt switch? and do I need anything else? can I use the stock thunderbolt coil and wiring this bad boy up to the coil. how does the coil know when to send fire on this unit?
 
Whoah! Lots of questions!

Simplest to quickly explain mechanical contact ignition:
Ignition ON..... Points closed..... coil is being saturated on the primary side.
A small Capacitor is involved.
Points break...... primary field collapses as the secondary side produces High Energy spark output.
(The coil acts as an AC "step-up" transformer, so to speak..... I.E., primary side/secondary side!)

The electronic ignition systems use: Hall Effect, Photo Eye, or VR.... (magnet reluctor) triggering that replaces the function of the mechanical contacts.

The coil doesn't know the difference...... however, I believe that your M/C TB coil is slightly different.
Best to use what Mallory recommends, IMO.

Mallory will also have instructions for use with the Mercruiser S/A!

The YLM is a three wire unit......... Negative, power, trigger.
Instructions are always included with new units.

The best aspect of the YLM, is VR triggering. No Hall Effect/No Photo Eye! IMO, that is!

.
 
buy the hole kit wires,coil,dist, you may be askin for trouble usin old coil!! i used delco kit like 329.00 i never have hooked the shift intrupter yet! i think the base timen was 8 degres instructions are very very good, u will be suprised how easy the job is trust me!!
 
NOTE: The Delco Voyager is EST, which would basically bring you back to what the TB system is!
Mallory is VR w/ mechanical advance!

Just pointing this out..... your call!
 
I deffinitly want to go with the mallory get rid of the electrical bull. Think Im going to have to wait untill after christmas is over before I buy myself a present lol I apreceate everyones advice and help on this, I am going to be one happy camper to get rid of the thunderjunk IV :)
 
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