5.7 TBI advanced timing

[zero lash]

I rebuilt a 5.7 the boat runs and starts great but to do so I had to advance my timing. When I have set the correct timing using timing tool and procedure for my boat that i got directly from mercruiser. My boat mph drops significantly. If I advance it runs great. My question is do I need to remap? The motor is stock except bored out 30 over and i have 4" exhaust. I dont see that as an issue. I have set the correct timing multiple times just to be sure.

 

[alldodge]

What is the serial number?
What timing did you set the motor at?

 

[zero lash]

0L012580 engine number. The procedure is calls for 8 degrees. I have it advanced from what I remember to be 10 or maybe 12

 

[alldodge]

Thanks for the number
With the EST ignition are you jumping the DLC connector which puts the motor is base timing mode?

 

[zero lash]

Yes I did.

 

[alldodge]

OK, when the jumper was inserted did the motor rpm change, or stay the same?

When the jumper was removed and motor was reved up how much advance are you getting?

 

[zero lash]

No it didn't rev up as expected.
I am not sure about the second question. Its been awhile since I did this.

 

[alldodge]

Might have a bad connection to the DLC connector and it may not be going into base timing mode. Right now I don't know

 

[zero lash]

So the chance of it needing a remap of the ecu is not the issue. It may be something that has to do with timing?

 

[thumpar]

If it wasn't in base timing mode then you wouldn't get a good timing on it.

 

[zero lash]

That's what I thought initially but, I was assured that only the Mag 350 will raise RPM's when put into base mode. My motor is not a Mag motor so I had to manually raise the RPM's. I set the timing multiple times because after I set it and took it out on the water I could only hit maybe 40MPH. If i advanced the timing I was getting around 48MPH. The boat has run fine like that for 4 years with no issues. Its just always puzzled me why?

 

[alldodge]

Try putting it in base mode and then increase the rpm some to see if timing advances. If it does advance its not going into base mode

 

[zero lash]

I have and it does advance.

 

[dubs283]

Have you checked what the full advance is?

That system should hit full advance by 2500 rpm or sooner

 

[zero lash]

No I haven't. Does it need to be about 19 degrees of timing at 2500?

 

[alldodge]

Check your DLC connector and see that pin A is Black/White and B is White/Black
Pin A goes to Ground and B goes to J1-7 on the ECM

The EST and ECM can provide a total of 27 degrees, which includes base timing