mjb

I have a '97 502 MPI. I want to check/set my base timing with a timing light. I thought all I had to do was ground out the ecm with a jumper wire to put it in base timing mode. There is a grey wire with a female bullet connection cliped to the inside of the ecm box. I was told that this is the wire I need to ground. Is it really that simple...I have read a lot of threads on OSO that seem to say I need a scan tool to set my base timing. If I can just use a jumper wire, will it go into base timing mode right away or do I have to rev the engine. Thanks for the help.

mjb

Come on guys- I thought this was an easy question. Surely someone has set MPI timing before. I want to set my timing tomorrow morning and don't want to screw anything up. Look'in for a little help. thanks-

JaayTeee

I don't have my manual handy here at work

Do a "search", I know it's been discussed here before.

You don't have to use the scan tool to do it.

articfriends

iTrader: (1)

I bought the merc timing tool,local marina had it,i think it was 12$ or something. I just unplug timing terminal(mine mounts ahead of computer to a plastic holder and has 2 wires). Warm boat up first,plug tool in,bring motor up around 1000 rpm's and aim the light. I been told you can jumper the timing portal with a paper clip or a wire,my boats already in storage or i'd go look and give you the wire color,Smitty

mjb

Thanks Smitty-

jdnca1

Don't know the MPI motor (maybe its the same) but on the 500EFI you jump pins A & B on the DTC connector for base timing...set to 8 degrees and you're done.

blownboat

Yup, jump a and b on a mpi,bring rpms to 1000, otherwise it jumps all over.

mjb

That seems simple enough...jump A and B. What is the single grey wire for??? Inside of the Metal ECM box, the is a small metal clip on the side of the box. It holds a grey wire with a single pin female bullet type connection. It was obviously put there by the factory for some type of easy service or calibration. I had one mechanic tell me to simply ground this wire to set timing but that sounds different than jumping between pins A and B. I've looked in the Mercruiser servise manual but they don't seem to make reference to this wire.

tssteph

Did this work for you? I have to do the same thing and don't want to buy a scan tool for my 350 mpi motors if I don't have to.

Brian