Merc. 3.0 timing stuck, Please Help

[Redphone107]

So I have been working on a vibration issue with the mercruiser 3.0 in our 2004 Maxum 1800 MX. I tried to set the timing. I went through the proper steps of attaching the jumper and bypassing the shift interrupt. I set the timing to 2 degrees ATDC (as the directions show for my model). the boat ran like crap and when I went through the proper steps to exit base timing, the motor did not advance back to 12 BTDC. Sooo, I set the timing (not in base timing) to 12 BTDC. The boat ran fine near idle, but vibrated under load at higher speeds.

Here's my problem:

I took it out on the lake today with my brother. He drove and I held the timing light to the motor. At idle, we had 12 BTDC. We tested at 2500 RPMs in neutral and 2500 RPMs in gear while driving the boat. The result was that the timing never advanced to the 25-27 degree BTDC that it should have. The timing remained at 12 BTDC while driving. I hope I am making sense here. No matter what we did, the timing never changed. It seems like the motor is stuck in base timing, meaning, whatever you set it at, it stays there and will not advance at all. I think this is why the boat is vibrating at higher RPMs: The lack of advance from idle at 12 BTDC to 25-27 BTDC at 2500-2800 BTDC.

Does this mean that the distributor is bad? Is there an electrical issue? Is there a ignition issue? Thanks, I'm just trying to figure out why the timing will not change at all.

Again, thanks for all the help.

[mmwjr]

First the jumper that should be installed is not to bypass the shift interrupt switch but to set the ECM into base timing mode. Are you sure you did this properly?

Timing advance is controlled by the ECM and yours seems like it's stuck in base mode. Also there are mechanical weights in the distributor that can stick but for you age boat I doubt this is the case plus you are not seeing an electronic advance from the ECM.

Just sounds like the jumper is still in place.

When did it last run good and what happened since then?

[Redphone107]

We just bought the boat 2 months ago and it has had a motor vibration since then. My wife thinks it's in my head, but I know motors and this one vibrates. I actually had two broken starter bolts and a broken power steering pump bracket.

I went through the procedures Monday at home with ears on the drive. What I figured out was that whatever I set it at (in what I thought was base timing) would remain and not advance or retard after removing the jumper. So, I took it to the lake yesterday to check the timing under load and had the same results. No advancing or retarding from 12 degrees BTDC.

And you are right. The motor acts like the jumper is still in place.

I posted to another forum and someone mentioned that the ignition module could be bad. I cross referenced on the internet this morning and Orielly's Auto Parts is having one delivered for pickup this afternoon. I am going to change that on the distributor and attempt to set the timing afterward. Is there something else that could be the problem? Thanks for your advice.

[mmwjr]

Regarding the vibration did you verify all 4 cylinders are firing? Compression test for health of each cylinder.

[doandaa]

Redline, I have the exact same problem with my 3.0: Ignition is stuck in base mode after disconnecting by pass switch ground and disconnecting the two white wires. Tried another ignition module and had the same results. Did you get your problem fixed? What did you do to get your 3.0 out of base mode? Thanks

[Redphone107]

Old thread I know, but I fixed the timing issue last year by changing the control module. It worked fine and the timing is good.

[mmwjr]

Glad you fixed it and thanks for the follow up.