Mercruiser Thunderbolt 5 ignition timing

[Jay Curtis]

ok the boat is a 1993 Crownline 21' cuddy 5.7 SN OF277191 at least that is what it is suppose to be

PO put an older motor in it 1st question is timing the manual says to ground a purple/whit wire that comes off the front of the distributor i don't have one ?

that section also talks about Knock sensors and a timing control module i dont see either of those

my distributor says thunderbolt 5 is it possible that on this age would not have the spark control?

i am also a little concerned about the knock sensors this motor has small chamber Dart heads so i am a little worried about spark knock if this distributor advances to far

i set my idle timing at 8 and can see that the spark advances when i throttle up but cant tell how far ( dont have a tape or adjustable timing light)

the motor would like a little more advance at idle but not sure a i dare with out knowing what the dist advance does

i more thing i have 2 ground wires in the harness that goes up to the water temp sensors with small lugs on them they are about the size of the wires that go on a coil i cant see any screws near them that would hold them down
any Ideas?

thanks for the help

 

[Fun Times]

Re: Mercruiser Thunderbolt 5 ignition timing

Serial number 0F277191 belongs to a Mercruiser Thunderbolt 4, W/PS, TWO PC EX, 5.7L ALPHA (1994) Model No: 457B100GS.

To confirm this is still your original engine serial number, Check to see if there is a metal tag located just above the engine starter with a number on it.

Since you have a Thunderbolt 4 ignition system, you will not have a wire to ground out to set timing at 8 degrees BTDC.

Also your model will not have the knock sensor system.

Where does it say you have the thunderbolt 5?

Have a photo of the 2 ground wires in the harness?

 

[achris]

Re: Mercruiser Thunderbolt 5 ignition timing

ok the boat is a 1993 Crownline 21' cuddy 5.7 SN OF277191 at least that is what it is suppose to be, PO put an older motor in it

Ohhhh, that worries me...

1st question is timing the manual says to ground a purple/whit wire that comes off the front of the distributor i don't have one ?

I looked up the serial number, and it looks like it has Thunderbolt IV, not V... That's would also be born out by the lack of Pur/wht wire to ground for timing.

that section also talks about Knock sensors and a timing control module i dont see either of those

TB-IV didn't have knock control

my distributor says thunderbolt 5 is it possible that on this age would not have the spark control?

The actual distributor for TB-IV and TB-V is the same. The difference is the ignition modules themselves. And some of the earlier V8s with TB-V didn't have the knock modules either....

i am also a little concerned about the knock sensors this motor has small chamber Dart heads so i am a little worried about spark knock if this distributor advances to far

i set my idle timing at 8 and can see that the spark advances when i throttle up but cant tell how far ( dont have a tape or adjustable timing light)

the motor would like a little more advance at idle but not sure a i dare with out knowing what the dist advance does

i more thing i have 2 ground wires in the harness that goes up to the water temp sensors with small lugs on them they are about the size of the wires that go on a coil i cant see any screws near them that would hold them down
any Ideas?

thanks for the help

The ground wires are just spares, or used in different engine models, or with different accessories.

Based on what you have posted, the best thing I can ask is for a close up photo of the distributor and the modules on it. Especially if you can see any numbers or letter cast in the plastic, or written on the modules....

I know I haven't given you much, but I hope it helps some....

Chris......

 

[Jay Curtis]

Re: Mercruiser Thunderbolt 5 ignition timing

Thanks guys i was upside down looking through my bifocals when i saw the V on the distributor i bet i just didnt see an I in front of the V or it is an early 5 with out the Module for the Knock Sensors,

that had me going i couldnt figure out how the PO could have taken off that module and made it look like it had never been there

Commander i know its not the original engine will post a pic of the wires, i thought sure the went to the dist but both have are solid
connections to ground

another wierd thing is that i had no spark untill i connected the outdrive oil container and it was empty havent tried to start since i filled it so if the float switch is changed now i may have no spark again

 

[achris]

Re: Mercruiser Thunderbolt 5 ignition timing

...another wierd thing is that i had no spark untill i connected the outdrive oil container and it was empty havent tried to start since i filled it so if the float switch is changed now i may have no spark again

That's just an alarm, nothing more. Nothing to do with the ignition system.

Question... Is this a 'no spark' thread or a 'timing' thread. I assumed you had the engine running and just needed to know how to set the timing....

Chris.........

 

[Jay Curtis]

Re: Mercruiser Thunderbolt 5 ignition timing

achris it is a TB IV not a V had to about stick my nose on the distributor to see it will start a new post with my wiring issues