93 3.0L Mercruiser Timing Stuck

[bigred95stang]

I just bought a 93 Baja 180 islander that maxes out the RPMs at about 2200 RPM. In the quest to find out whats wrong, I have downsized a prop (14.25x17) changed the plugs, wires, cap, rotor, fixed a vacuum leak, changed the oil, etc. Compression was all around 175. I finally got around to checking the timing (EST timing system) and set it (with the jumper wire in and the shift interlock unplugged) to 1 degree BTDC. Once I pulled the jumper and repluged the shift interlock back in, the timing did not move from 1 degree. I figured the ignition module was bad so replaced it. Timing is still stuck at 1 degree. If I rev the motor to 1500 it will move a couple of degrees to about 6-8 degrees but thats it. Timing is steady. I assume that I still have a bad ignition module but are they bad right out of the box that often?

 

[Don S]

Re: 93 3.0L Mercruiser Timing Stuck

Did you have the engine running when you put it in base timing mode and took it out of BT mode?

 

[bigred95stang]

Re: 93 3.0L Mercruiser Timing Stuck

I put it into base timing mode before I started it. When I checked it to see if it was adjusting timing, I restarted the motor after I took it out of base timing mode.

 

[Don S]

Re: 93 3.0L Mercruiser Timing Stuck

Here is the timing procedure from the OEM manual. Putting it into BT mode and taking it back out of BT mode should be done WITH the engine running.

Timing Procedure

IMPORTANT: Failure to follow the timing procedure
instructions will result in improper timing
causing performance problems and possible severe
engine damage.

1. Start engine and allow to reach operating temperature.
2. With engine running, install a jumper wire across
the two WHITE leads on the distributor using
(91-818812A1), or fabricate one using a 6 in. (150
mm) section of 16 gauge wire with two male bullet
terminal ends connected.
3. Bypass the shift interrupt switch by disconnecting
wires at shift interrupt switch. Temporarily join the
engine harness wires together.
IMPORTANT: Do not fail to reconnect these two
wires to the shift interrupt switch when timing
procedures are complete.
4. With timing light connected, check timing. Timing
should be 1? BTDC.
5. If required, loosen distributor hold down clamp
and rotate distributor to obtain specified timing.
6. Secure distributor hold down clamp, and recheck
timing as above.
7. Reconnect the two wires to the shift interrupt
switch. Remove jumper wire at distributor white
leads.
IMPORTANT: Be sure to remove jumper wire before
returning engine to service, otherwise timing
will not advance.
8. With timing light still connected, and engine at
IDLE, verify that timing did advance to 12? BTDC,
(plus or minus 2?). At 2400-2800 RPM maximum
(total) advance is obtained and should be 27?
BTDC (plus or minus 2?).

 

[rodbolt]

Re: 93 3.0L Mercruiser Timing Stuck

after following DonS's advice, yes I have seen failures out of the box.
some years back I had a 3.0 that would not advance,replaced the module and retested, it would actually start retarding to about 18* ATDC and the engine would all but stall.replaced it again, this time no advance, third module was a charm.
cant tell you why but the lack of advance on the EST in the 3.0 is something I have seen 8 or 9 times in the past 2 years or so, never saw it on a V application only on the 3.0.
dunno why
but do double check your method before scrapping the module.

 

[bigred95stang]

Re: 93 3.0L Mercruiser Timing Stuck

I just got back from the autoparts store (I know marine parts are different but thought what the heck) and had them check the orignal AC-Delco ignition module. They said it was fine. I also just double checked the wiring harness to make sure the two leads werent shorting together (they werent).

One quick question, when you bybass the shift interuptor, do you just unplug one wire or do you unplug both and then plug the two seperate wires together, in effect "closing" the circuit?

 

[Don S]

Re: 93 3.0L Mercruiser Timing Stuck

One quick question, when you bybass the shift interuptor, do you just unplug one wire or do you unplug both and then plug the two seperate wires together,

Have you even read and tried to understand the instructions I posted above?
Read step 3. Did it say just unplug one wire? No, it said unplug both wires and temporarily connect the harness ends together.

 

[bigred95stang]

Re: 93 3.0L Mercruiser Timing Stuck

Easy Don. I greatly appreciate your help but I didnt completely understand that step so I wanted clarification before I go put the boat in the water and do it wrong again.

 

[Don S]

Re: 93 3.0L Mercruiser Timing Stuck

You don't have to put the boat in the water to set the timing, doing it on muffs works fine and shows the same thing.

 

[bigred95stang]

Re: 93 3.0L Mercruiser Timing Stuck

We took it out to play today. When I connected the two shift wires the engine died. I had to advance the timing a bit to get it started again and finally got the timing adjusted. I can now get the RPMs up to 2600 but can easily cruise at 2000 RPM at 50% throttle. I plan on checking TDC and the timing mark sometime over the off season (I think today was our last day) to see if there is more there since from about 75% to 100% throttle there is only about 50 RPM change.

 

[bigred95stang]

Re: 93 3.0L Mercruiser Timing Stuck

I was able to visually check TDC today and from what I could tell each time it looked like the piston was TDC I was within two degrees on the damper so that checks out ok. I double checked my timing and it was spot on. I just wish I had an adjustable timing light to check exactly how far it was actually advancing. Thanks for the help so far!