Mercruiser 3.0

[MattH1900SC]

Really need your help - I am new but this forum looks to be rich with knowledge.
Engine: 3.0 Mercruiser 2001 with Delco EST ignition.
Symptoms: Whilst out on the water the boat stopped and we had to be towed into port. Fuel pump was very lazy so I initially thought it was the culprit. It was bad as fuel was entering the vent pipe so needed to be changed. Whilst at it though, I thought I would replace the ignition components for belts and braces . Here is what I have replaced:
Fuel Side:
- Fuel Tank pickup
- Anti-Siphon Valve
- New water separation filter
- New fuel pump
- Rebuilt carb
Ignition:
- Coil
- Coil Pickup (Car derived)
- Ignition Module (Car derived)
- Cap and Arm
- HT Leads and Spark plugs

All worked great apart from the fact that the module and coil pickup are car derived meaning:
- The module doesn't cut the spark on gear shift.
- The ignition advance isn't right (confirmed with my timing light)

I then bought a Marine Ignition Module and installed it, now I get random cutting out. The module will now cut the spark when going into gear and in addition it will l just stop the spark (I have an inline tester and I can see it just cut) at random, hot or cold. I removed the feed from the switch to the module to isolate whether it was the cause or not, but the same behaviour is exhibited. Does the pickup and module need to be a matching pair?

- Installed new module (with heat paste)
- Attempted to start the engine – didn’t start
- Installed spark tester (Between lead and spark plug) – no spark
- After a bit more cranking, it started to spark and the engine started
- After 5 minutes, the engine stopped
- Engine would restart intermittently but would then stop sparking and conk out
- Re-installed the car derived ignition module and all the above went away – it started and rev’d for over 10mins. Went out for 30mins at full throttle and no problems with consistency.

What do you reckon, is the car derived coil pickup incompatible or is it just a dodgy ignition module.

 

[itsathepete]

Is the marine ignition module an OEM part. Some aftermarket ones are "dodgy" in your terms.

 

[MattH1900SC]

Thanks for the reply, it has no identifying marks. It was less than half the price of a genuine "GM" version.

Will also add, when running, the idle and pickup is really nice, no stuttering just a little flat due to ignition curve

 

[itsathepete]

Thanks for the reply, it has no identifying marks. It was less than half the price of a genuine "GM" version.

Will also add, when running, the idle and pickup is really nice, no stuttering just a little flat due to ignition curve

An engine that runs great when it runs, but doesn't run reliably, doesn't run great.

 

[Grub54891]

how's your lower shift cable? if it's sticking you will have these issues.

 

[MattH1900SC]

Hi,

It appears to be ok, I also removed the connector with the signal wire to the module and still the same behaviour. Unless it works in a different way to what I am thinking...

 

[aidanmurphy]

I am going to go with the dodgy ignition module. I had the same exact symptoms when my ignition module started going. I replaced it with an OEM equivalent and no issues since

 

[alldodge]

I then bought a Marine Ignition Module and installed it, now I get random cutting out. The module will now cut the spark when going into gear and in addition it will l just stop the spark

Saying going into gear and not out of gear. The interrupt switch on shift plate should only work when boat is in the water and only when coming out of gear

I removed the feed from the switch to the module to isolate whether it was the cause or not, but the same behaviour is exhibited. Does the pickup and module need to be a matching pair?

Does "removing feed from the switch" mean the shift interrupter connection was removed?

The pickup and module does not need to match but they do need to be good parts.

 

[MattH1900SC]

Hi everyone,

Thought I would loop back as it may help others.

I installed a new Sierra module and it hasn't missed a beat since. Used it 3 times and has performed well. Point to note, the automotive module gave the engine a very flat nature, was very lethargic (all to do with the ignition curve). The Sierra module, with the correct serial number, has restored power and good engine characteristics. Don't cheap out, get the correct module.