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New 3.0 in older boat

RicardoMarine said:
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.
Click to expand...

Be careful doing the idle mixture this way.
There are many factors that can influence this method.


I would take the simplest path, do it by max rpm. results are the same but rpm is easier.



DISREGARD ADVANCE Spew........PCR doesn't understand the ignition system for this product.......If he did he wouldnt need to add this AGAIN TO ANOTHER THREAD!

Hale PCR!!
 
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kghost said:
Be careful doing the idle mixture this way.
There are many factors that can influence this method.
please elaborate!


I would take the simplest path, do it by max rpm. results are the same but rpm is easier.



DISREGARD ADVANCE Spew........PCR doesn't understand the ignition system for this product.......If he did he wouldnt need to add this AGAIN TO ANOTHER THREAD!

Hale PCR!!

Sheesh..... childish and immature post count envy is once more present.
Click to expand...


Jack, I picked this up for you. When it arrives, please read it!

416TA7tk9cL._SX384_BO1,204,203,200_.jpg





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Between 16 and 14 with 15 in the middle at idle. As I revved the motor up to 2k the needle steadies somewhat but still vibrates. I'm almost suspecting maybe the dist is bad although I did install a new rotor and chip. Doing a compression check tomorrow to rule out head gasket. Being a brand new engine, I hope this is not the case but checking the oil I did not see any signs of water or combustion blow by. I still think it's ignition related because it sounds like it's missing.
 
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At idle, on a 4 cylinder engine, the vacuum reading fluctuation (i.e., unsteady instrument needle) will be greater due to only 4 complete intake strokes occurring during 720* of crankshaft rotation.
In other words..... you will see 180* crankshaft rotation to complete an intake stroke, followed by another intake stroke during the next 180*.

Whereas with 8 cylinders, the engine sees 8 complete cycles during 720* of crankshaft rotation.
In other words...... you will see that same 180* crankshaft rotation per cylinder to complete an intake stroke, however, it will be followed by another intake stroke in only 90*.


Use the P of E.


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Idle mixture has zero to do with rough running at higher RPM. That's handled by the size of the carb jets. Are you using an old carb on a new engine? That's prolly where the issue lies. Doubt it's ignition as it seems to fire and run.
 
John4003 said:
Okay I installed a new GM 3.0L in my 2001 Sea Ray 180 and everything is ready to go. It runs but I am a little unsure of where to set the timing. Do I go by the manual for the boat year or should I go by the Engine year?
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Since the engine long block is new, set it up, run it, break in the cam following mfg suggestions. Get the engine up to temp then after this is done start looking into the possible rough running issue.
 
Well as a test to make sure my gauge is good, I hooked it up to my 4 cyl car and it was steady. Also taking it up to 2k it still was vibrating but just barely.
 
Well adding the new carb and ignition parts was due to the poor running before. So with all the new parts, it at least stays running now but runs rough and sounds like it's missing and the vacuum gauge kinda confirms this.
 
OK that's the first time in this thread that you mention a new carb. As Chris says, get some time on it then see where you are. Be sure that the jets are the proper size. Roug running could be a lean condition and you won't know until you can look at the spark plugs whether they're grey white or black.
 
I may have found an issue. The specs listed for the new motor have the firing order 1,3,4,2. The Setec manual list it as 1,3,2,4. Sheesh how do I confirm this? Guess I just have to try it.
 
I pulled a couple plugs yesterday and they had some black soot so I did lean out the idle just a bit. I'm going to do a compression check and pull the dist and do some testing on it also. The new carb allowed it to stay running so I could set the timing but had no effect on the miss.I guess it is also possible a valve might need adjusting which would piss me off because it's supposed to be a brand new GM motor.
 
.."The specs listed for the new motor have the firing order 1,3,4,2. The Setec manual list it as 1,3,2,4. Sheesh how do I confirm this?"

Swap those two plug wires with the motor running and you'll know.

Jeff
 
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John4003 said:
I may have found an issue. The specs listed for the new motor have the firing order 1,3,4,2. The Setec manual list it as 1,3,2,4. Sheesh how do I confirm this? Guess I just have to try it.
Click to expand...

Be careful when using the Seloc manuals.... lots of errors in them.
The correct firing order for the GM 3.0L 4 banger is 1-3-4-2.

#1 cylinder is always the furthest cylinder forward.

GM 3.0L firing order .png




John4003 said:
I pulled a couple plugs yesterday and they had some black soot so I did lean out the idle just a bit. I'm going to do a compression check and pull the dist and do some testing on it also. The new carb allowed it to stay running so I could set the timing but had no effect on the miss.I guess it is also possible a valve might need adjusting which would piss me off because it's supposed to be a brand new GM motor.
Click to expand...

John, technically speaking, there is no adjusting the valve(s). You will be adjusting the depth of the hydraulic cam follower's plunger as per OEM specs.

See post #22 again regarding the 4 stop procedure.




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Suggestion:

Perform your cylinder pressure test prior to adjusting the cam followers.
Should you find a weak cylinder, it may be covered under your warranty.

In other words, do not disturb any evidence that may show that they were not adjusted properly.




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John4003 said:
I pulled a couple plugs yesterday and they had some black soot so I did lean out the idle just a bit. I'm going to do a compression check and pull the dist and do some testing on it also. The new carb allowed it to stay running so I could set the timing but had no effect on the miss.I guess it is also possible a valve might need adjusting which would piss me off because it's supposed to be a brand new GM motor.
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How much have you actually run this engine? 20 hours? 50? 2? Sooty plugs means that the main jets are too big. Idle mixture has nothing to do with it. All that does is keep it from stalling with the butterflys closed. Don't tune the engine at idle, as that has very little impact on overall performance.
 
About 20 minutes. I pulled the plugs again today and they still have some black and a small amount of oil which I am guessing won't go away til the rings seat. I pulled the dist and checked it out and everything is good so has to be something else. Jets too big on a brand new carb? I don't know if that's it because then why does it miss at 2k also? The vacuum gauge was fluttering between 14 and 16 and somewhat smoothed out as it got closer to the 2k rpm mark which points to ignition issues.
 
I guess you don't understand how carbs work. When you buy a carb that's not specifically pre-tuned for your type of engine, you have no idea whether it is going to be rich or lean when you run it. in your case it's probably way over carbed which is why its running rough and leaving soot on the plugs. It misses at 2K cz there's too much fuel in the mix which is putting out the fire. Smooth running at higher rpm is probably more due to harmonics.
20 minutes isn't enough time. Run it a couple hours before you start the chicken dance.
 
No I'm not a carb expert and you may be right. It may be causing it to run rich but the carb was supposed to have been set up for this engine. I've contacted the people I purchased it from to see what they say and hopefully they get back to me. In the meantime I may open up the old carb and rebuild it myself and see if it makes a difference. Oh and why does it run like crap at idle? I adjusted the idle screw according to the manual.
 
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What are the results from having firing order correct?

Why is there posts on adjusting valve/rockers?

Was the engine pre-assembled ? Or did you install the heads?

If it was preassembled odds are it is ok.
If you are not hearing any clacking it should safe to say it is ok for now.

Why anyone would suggest adjusting the valve/rockers regardless of the method is insane!

PCR.....ugh.

You can not compare a carbed marine 4 cyl engine to an automotive especially if it has EFI...


4 cyl gm mercruisers are notoriuos for vibration.
It is luck of the draw if they dont!!
 
I actually had it correct in the first place so that's not the problem.
Engine is a brand new from GM.
I remember now why I hate carburetors.
I can't get it to idle at 700. It bucks and sputters until I raise it to about 1k.
The engine is a little noisy but it sounds like the ones I hear in video's. Just not as smooth and has that damn miss.
 
Post a video of yours running. 3.0 I had for 20 years wasn't what I would call smooth, nor quiet engine, but was very durable

Rest assured if you bought a new base engine it is ok and you do not need to adjust anything. Only concern would be to properly break in the cam (as this is a fact tappet) by keeping rpms up at 2 k for 20 minutes and use oil with zinc in it like Rotella or use a break in additive. Then move on to adjusting it in.

Did you reitighten the intake to head bolts and carb to intake bolts? Is the new carb a OEM or remanufactured or aftermarket? Possible a new carb is bad, more possible if it is a remanufactured.

one question what carb to intake gasket was used, last time I rebuilt the mercarb on my 3.0 the kit came with two base baskets one with a oval single hole and one with two round holes (that matched the factory one). I found it odd that the factory base gasket had two holes but the manifold has one oval hole, so I tried the oval gasket (maybe that's for a TKS carb?)... could not get the thing to idle well and idle mixture screw didn't work right, basically had no effect on idle quality. Swapped out single holegasket for the two hole one and it worked great. You should be able to lean out the idle mix till it stumbles, fatten it up till it stumbles, usually best in between these two points. If yours doesn't act similar I suspect there's something with the carb.

you may hate the carb now but you can fix it with simple hand tools vs mpi where you need the software.
 
Yes I re torqued everything. I'm following the break in instructions that was sent with the motor and so at this point can't take it above 2k. I'll check the gasket that came with the carb but I think it was the two hole one. Man not sure now but I can see where that would make a diff. Here's the vid of it running before I tried to take the idle down to 700. So here it never went below 1k rpm.
 
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