1994 Mercruiser 5.7 timing issue- no purple/white wire

[dhrmx5]

Hi. Cant find a white/purple or purple/white wire to put the TBV ign into timing mode. The only wires laying on top of engine are the shift interrupter and the purple wire that services the coil (and I presume excites alt) and goes forward to the kill switch on the dash. It does run on top of engine towards the fuel pump area but does not connect to anything that I can see. I am using it to energize a relay for power to the electric fuel pump I installed (original was mechanical). I replaced the cracked engine with one out of a 93 Suburban which is why I had to install the electric pump. Boat runs out great and easily pulls to 5K rpm (I guessed at the timing setting) so it isn't a runability issue. Just want to get the timing right. Boat is a 94 Reinell 19BRXL with 5.7. Original engine serial number represents what I am running. Only longblock was changed.

 

[dhrmx5]

Upon further study it looks like the boat has TBIV ignition. I can't seem to find the timing info online.

 

[nola mike]

Upon further study it looks like the boat has TBIV ignition. I can't seem to find the timing info online.

No base timing mode on TB IV, just set it at idle.

 

[dhrmx5]

No base timing mode on TB IV, just set it at idle.

Thanks for the reply. I had thought the TBIV was a big module but this website showed me it was a small one with the same plug I had seen already. I wasn't sure if I still needed a wire to set the base timing. Thanks

 

[Jeepmike]

Just to ask a follow up, when your setting the timing on the thunderbolt IV do you just put the line at the big notch in the V? Because mine is a little before that

 

[dhrmx5]

Just to ask a follow up, when your setting the timing on the thunderbolt IV do you just put the line at the big notch in the V? Because mine is a little before that

If you look at the timing marks on the front of the engine you can see the number for each pointer. The numbers get bigger as you go counter clockwise. Deepest notch is 0, on the right end of the marks. So 4 marks (peaks) counter clockwise should be 8 degrees before top dead center

 

[dhrmx5]

 

[Jeepmike]

Hmmm yours looks like mine. Good to know. Thanks. How's mine look?

 

[Jeepmike]

Closer pic

 

[Scott06]

Closer pic

Looks like you are at Two degrees btdc

 

[dhrmx5]

Closer pic

Sorry forgot to respond. Scott06 is correct. When you bump your timing the rpms will likely increase. reset idle and check timing again.

 

[Jeepmike]

Sorry forgot to respond. Scott06 is correct. When you bump your timing the rpms will likely increase. reset idle and check timing again.

Don't I have to retard it 6°? I would have thought the rpms would drop no?

 

[Scott06]

Don't I have to retard it 6°? I would have thought the rpms would drop no?

Im pretty sure you need to advance it 6 degrees to 8 degrees before. Your crank shaft will be turning clockwise viewed from front of engine.

 

[dhrmx5]

Don't I have to retard it 6°? I would have thought the rpms would drop no?

The scale shows BeforeTopDeadCenter also known as BTDC. You should set it for 6-8 degress BTDC, depending on the quality of the fuel you run.

 

[dhrmx5]

In response #6 I mistakenly used the word peaks when I meant marks. Each mark is 2 degrees.