Mercruiser 5.0 carb?

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,446
Defective Ignition Module, or the Module is somehow being shorted to Base Mode all the time
 

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,440
it does not advance at all. any suggestions.
This is not in base mode correct ?

Module needs replacement then. You have the thunderbolt V ignition which is fantastic unless u need a new module. Would look for a used module on eBay. I have bought them for around $200 used. New they are expensive enough that people will replace the entire ignition system with a Delco EST
 

pjs1183

Cadet
Joined
Aug 5, 2023
Messages
17
correct. when i ground out you can tell its in base. It acts different. But u grounded still no advance
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,446
Before you go replacing the Module, check the wiring Harness for signs of abrasion, pinched wires, loose connections, etc.
 

pjs1183

Cadet
Joined
Aug 5, 2023
Messages
17
i just did that. everything looks good. The purple white isn’t grounded. i check.
 

pjs1183

Cadet
Joined
Aug 5, 2023
Messages
17
i went through everything one last time. It has power and is grounded.
The yellow wire has power all the way through.
the alarm wire never gets 12v or any. idk why
pretty sure the shift interrupt doesn’t work. It was on the red/white on the cap and i moved it to the white blk and it was a ***** to switch gears.
Everything else seems to be in order. The white red and green are spliced to make it longer but i don’t think that should affect it.

Should i change anything else before hitting the bullet?
 

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,440
i went through everything one last time. It has power and is grounded.
The yellow wire has power all the way through.
the alarm wire never gets 12v or any. idk why
pretty sure the shift interrupt doesn’t work. It was on the red/white on the cap and i moved it to the white blk and it was a ***** to switch gears.
Everything else seems to be in order. The white red and green are spliced to make it longer but i don’t think that should affect it.

Should i change anything else before hitting the bullet?
That has a knock sensor module is the sensor or module non functional and causing it to go into timing retard mode constantly? Unfortunately the nimrods at merc set this up to need like 9 v supply from knock module to the ignition module to keep it fro retarding timing.
Below is an except from the manual on how this works.
would -
see if it is supplying the 8-10 v the ignition module requires
if not supply verify it is not knocking looks for signs of detonation on plugs and piston tops . Possible you have a bad knock system retarding timing.

would be surprised if you have no advance over initial base timing that you would even be able to get to 4 k
 

Attachments

  • IMG_4385.png
    IMG_4385.png
    381.3 KB · Views: 2

pjs1183

Cadet
Joined
Aug 5, 2023
Messages
17
i discounted that to see if anything would change. Nothing changed.
So it’s possible that i have a bad sensor or module. I’ll check voltage in the morning.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,342
Hi. Before all that….
What is the ratio on the outdrive ? What did the 5.0 replace ? Was it a 5.0 or a 5.7 ?
If you have a 1.47/1.5 ratio outdrive, then it might explain some of what you have now perhaps. Think it was mentioned previously, but there isn’t such a thing as a factory prop.
 

pjs1183

Cadet
Joined
Aug 5, 2023
Messages
17
i believe these were powered by 5.7 volvo. It’s been re-powered with this merc. I got ordered in otherwise i’d test the volts still.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,342
i believe these were powered by 5.7 volvo. It’s been re-powered with this merc. I got ordered in otherwise i’d test the volts still.
That being the case…check that gear ratio. Your issue could be that you’re now over propped with the less powerful engine.
 

pjs1183

Cadet
Joined
Aug 5, 2023
Messages
17
So went out today. 12 V to the knock sensor. Not sure what’s going to the ignition.
retimed, set carb
one of my valve covers had vacuum line going to the back of my carb. i though both go to the flame arrestor.
Moved that.

Idk what happened but at 2500 rpm i finally had a timing change. by about 20 degree. Find out tomorrow on the river.
 

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,440
So went out today. 12 V to the knock sensor. Not sure what’s going to the ignition.
retimed, set carb
one of my valve covers had vacuum line going to the back of my carb. i though both go to the flame arrestor.
Moved that.

Idk what happened but at 2500 rpm i finally had a timing change. by about 20 degree. Find out tomorrow on the river.
Willing to bet your knock system is retarding . Its not the 12 v to knock module its the 8-10 v from knock module to ignition module that is what keeps it from pulling timing out. If yiu see it not advancing i would either get a inline resistor like in a older style points and supply 9 ish v to the igntion module on the knock sense wire.
 
Top