V6 Idle Stabilizer Module

[MaggieRose]

I just finished rebuilding my 150 HP Offshore. Linc and Synched her, set max and idle timing ran fuel pump, lube injector tests and also tested the lube alert module system.

Sea tested her Monday for the first time with a three hour run around the islands of Boston Harbor varying speeds never hitting WOT, occassionally bumping 3/4 speed. I figure a couple more days like this and this baby should be broke in good. One question though..

I have seen posts on this site recommending the removal of the Idle Stabilizer Module on Merc V-6 engines and capping the leads. Any comments?

 

[j_martin]

Re: V6 Idle Stabilizer Module

What that module does is lower the bias voltage on the switchboxes to advance the timing a few degrees if the idle speed goes below the set point. (methinks 700 rpm) If it also has the advance function, it advances the timing from 19 degrees to about 23 degrees at 5000 rpm, then retards it to 17 degrees at 5500.

If the engine is in decent tune, idle stabilization should not be needed. The high speed junk is just that, junk to protect the holder of the warrantee insurance.

Further, if it dies shorted and pulls bias to 0, that will advance the engine to over 30 degrees, and usually instantly grenade it at WOT.

The usual recommendation is to remove it (might as well just take it completely off) and set initial WOT timing to 23 degrees, and idle to where it runs right.

hope it helps
John

 

[hkeiner]

Re: V6 Idle Stabilizer Module

J-Martin,​

I read your comments and it got me thinking that perhaps I should remove the idle stabilizer from my 1996 150HP V6 motor. The motor runs fine and my first inclination would be to leave the motor alone. However, your caution that a failure of the stabilizer could cause "the engine to grenade" caught my serious attention. So that I get the new timing adjustment correct if I remove the stabilizer, I wanted to confirm my understanding of your instructions on setting the MAXIMUM timing.​

The link and sync specs for MAXIMUM timing adjustment with stabilizer installed are 21 degrees @ CRANKING speed (when cranking the motor with the starter) and 19 degrees at WOT (when running the motor at full throttle on the water). I understand that the 2 degree difference between CRANKING and WOT timing spec is due to the inherent nature of the ignition system.​

You suggested to "set initial WOT timing to 23 degrees", which is 4 degrees higher than the 19 degrees spec at WOT. According to this, if I set the MAXIMUM timing at CRANKING speed, the timing should be set 4 degrees higher than the 21 degree spec, which would be 25 degrees at CRANKING speed. Have I got this right? Alternatively, did your use of the term "initial WOT timing" mean MAXIMUM timing at CRANKING speed, which would be 23 degrees at CRANKING speed? I ask because MAXIMUM timing is initally set at CRANKING speed and then later confirmed at WOT.​

I hate to hijack this thread but your comments may be helpful to many other boaters with stabilizer units still on their motors. I don't want to remove the idle stabilizer from a motor that is running fine and then incorrectly reset the MAXIMUM timing (because of my misunderstanding) causing the motor to grenade. That would be sad...​

Thanks in advance for any confirmation and peace of mind that you can offer.​

 

[MaggieRose]

Re: V6 Idle Stabilizer Module

GOOD questions, also had me wondering. I have read numerous posts on retarding WOT timing an additional 2 degrees to compensate for the ethanol that is now gasoline. Will setting WOT timing at 23 degrees BTDC cover this?