Mercruiser 3.0 timing stuck at 12 BTDC, Please help.

[Redphone107]

So I have been working on a vibration issue with the mercruiser 3.0 in our 2004 Maxum 1800. 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.

 

[boatman37]

i'm new to boat engines so let somebody else verify first. i have never had the distributor cap off of mine yet sooooo...on a non computer controlled car engine there are mechanical weights in the distributor that advance the timing as RPM increases. there is also a vacuum advance. if this is how a boat engine is set up then i would start with looking to make sure the weights are freed up.

can anyone confirm this?

 

[flyman219]

I'll bet you have a burned out ignition module. This is what controls the advance. The control module is under the distributor cap. Napa has one for about $100 TP 59 I believe and there's the Delco D1965A at about $70 and of course the Mercruiser OEM. Be sure to cross reference your motor's module to be sure these may match before you buy one.

If the timing is not moving up in advance with the RPM's I'm sure your module is toast.

Mike

 

[RaceCarRich]

I was thinking module also. I'm told some places can actually test your module but not sure where.

'04 should not have mechanical or vacuum advance, only electronic in the module.

 

[flyman219]

Napa should have been able to test mine but they didn't have the right cable set for my unit. Check your local Napa and see if they have the right cable set.

Mike

 

[Redphone107]

Thanks guys. That is great info. I cross referenced the 811637T (which my model calls for) with Napa and Oreillys and have one (a BWD CBE121) coming to the store today. Along with that, I going to replace the cap and rotor. Plugs I have done previously. I will install tonight and reset the timing with the correct procedure. I will post back on what happens. Thanks for all the help!

 

[flyman219]

Be sure to put a smear of the heat transfer paste (NOT DIAELECTRIC GREASE!) on the bottom of the module before you install it in the distributor. This will save the module. You need this or you will overheat the new module and destroy it. You may get a small serving of this paste with the module, use it. If not buy some at the parts store before you leave.


Mike

 

[Redphone107]

Cool. Thanks for that. I will make sure there is some in the box or buy some.

 

[Redphone107]

Good news. It worked well. I changed the ignition module and fired it up. The vibration was less and I could tell that the timing was advancing to where it should. Got a total of 25 Degrees BTDC at 2,500 RPMs. Motor ran smooth. Compression tested all cylinders except #4 because of the sleeve issue. 110-120 on all three. The boat seems to run really good. Thanks!