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Which year ignition system are you using on the NEW 3.0L engine....... 2001 or 2019?
Use the timing specs provided by whoever sourced the engine for you, if you want to preserve the warranty .....the timing for a 'new' GM 3.0 should be about 19 deg BTDC at full advance (4000 RPM).
You would also be wise to follow the break-in procedure as well....
Do you check the advance without the dist in base mode?
The 3.0 ltr shake and bake. Run it. They never really run smooth.
New fuel, filter and anti siphon valve.A couple of a couple if thoughts in addition to setting the timing to factory spec.
Intake to head or carb to intake vacum leak That's what I want to check out next. I followed all the specs for torque installing the manifold but not really sure how to check for leaks since there is no place to connect a vacuum gauge.
are cap and rotor and plug wires in good condition! Brand new.
said new carb new or rebuilt? Did you set idle speed and mixture on carb per tune up specs in manual, verify float level ? Choke fully open when warm? Try swapping old carb if it ran better New carb. It runs better with the new one but still runs pretty rough. I need to work on getting the idle set correctly.
how long did it sit ? Is it possible that fuel is contaminated ?
Brand new engine so hopefully cam and lifters are good. I've replaced just about everything. I'm hoping it's just me missing something adjustment wise.
That is precisely my point regarding the suggestion of the P of E.
If you perform the 4 stop, you will have eliminated that as a possibility.
One thing I did bad was before I installed the motor, I had a brain fart and turned it backwards about a qtr turn but I don't see where that would hurt anything.
No.... you did not hurt anything by doing that!
Didn't think so. I think I need to go back and re-adjust the carb mixture screw and get the idle set and then re-time it.
After the boat is all together and run in, set up your base idle and mixture with the boat in the water, in gear and moving... Best proven way to set up the shake and bake.
That's the plan. The manual says turn the mix screw out 1-1/8 turns to start but that seems really rich and the plugs showed some soot. I've been told it should be more like 3 turns. Thoughts?
Temporarily install a vacuum gauge.
When adjusting the low speed mixture, shoot for the greatest vacuum reading.
You may need to simultaneously adjust the idle stop screw.
NOTE: the GM 3.0L in a Marine application is prone to what we call "run on" or "dieseling" upon shut down.
This is often caused by a lean air/fuel mixture and high cylinder temperature directly after a run.
You can address this later on!
The important aspect will be to see that this engine receives the correct ignition advance during the run-in period.