Adjusting maximum advance timing at high RPM

[hezzy602]

Boat-1985 4.3 GM262ci MCM205 4bbl

My Thunderbolt ignition system took a dump on me so I installed the Delco Voyager EST Marine Electronic distributor kit. I have my base timing set at -4 based off of their charts, which I am assuming means 4 degrees before top dead center, 4 degrees to the left of the zero mark on the tab mounted above the wheel. I am questioning that because the chart they give me, i am the only engine set for a negative number, all the other motors state 8,10,12,2. I cant be the only motor that calls for timing before top dead center...... a lil confused. It doesn't seem to run as smooth as other settings that i was playing with. For example when I give it a lil throttle from idle it hesitates for a split second. Their charts state that my max advanced timing should be 20 at 4600 rpm.

Is the only way to check max advanced timing is in the water? Do I really need those fancy adjustable timing lights or will my basic one work?

And why does it seem to run smoother on different base timing settings?

Just wanted to see your guys input before i called their office.

 

[achris]

Re: Adjusting maximum advance timing at high RPM

I've always found that using the Voyager dissy is a bit hit and miss. Some work fine, most don't. The best option is to replace the TB-IV module with a new one. I understand it's quite a bit more expensive, and Merc need shooting for that, but it's the only way to keep the ignition system performing the way it should.

OK... that all said, you have the Voyager unit and you need to make it work. You could spend the money and buy one of those nice 'fancy' advance timing lights (I have one and LOVE it), or just buy a timing tape and put it on the balancer. The end result will be the same. The other thing you need is the advance curve for that engine. It's in the Merc service bulletins, and the service-manual. I have already uploaded it, so I have posted it here for you....

As you can see, the maximum timing should be 14 degrees (plus initial advance), and at 2500rpm....

Chris......

 

[hezzy602]

Re: Adjusting maximum advance timing at high RPM

Thanks a lot for the info.
So what this and you are telling me that this new kit doesnt change any of timing......
WHy in the example it is saying 22 degrees for total advance.
WHy do you think the manufacture would spec for 4btdc idle timming and 20 for advanced......

 

[achris]

Re: Adjusting maximum advance timing at high RPM

MERCRUISER specify 8BTDC and a total module advance of 14 degrees, at 2500rpm (that's where the 22 degrees comes from). What the Voyager dissy specifies has nothing to do with the specs Mercruiser call out (but it should. And this has been the problem with the Voyager dissys all along. They say they are a direct replacement, but they are most definitely NOT! The wiring is different, and advance curves are different.) If you want it to run the way it did with the Thunderbolt system, set it up the same way, AS PER MERC'S SPEC, not Voyager's. If the Voyager dissy can't or won't set up the same, take it back and get a refund, and buy a TB-IV module. If it can't set up the same as the unit it says it replaces, you have grounds for a refund.

Chris......

BTW, what part of the Thunderbolt system died? (and how did you test it?)

 

[Bondo]

Re: Adjusting maximum advance timing at high RPM

Thanks a lot for the info.
So what this and you are telling me that this new kit doesnt change any of timing......
WHy in the example it is saying 22 degrees for total advance.
WHy do you think the manufacture would spec for 4btdc idle timming and 20 for advanced......

Ayuh,... Try it at 2? for the 22? total timin',...

It may well run at 24?, without detonation,... Testin' will tell ya,...

 

[dan t.]

Re: Adjusting maximum advance timing at high RPM

The Voyager (tbi truck distributor under another name) has 22 degrees of advance so "0" would give you 22 total or as Bondo says try it at 2 for a total of 24. It should be fine, just listen for ping under load. You can set these up at total when reved up to 3000 rpm, just dont hook up the bypass, rev it to 3000 and set it to 24 degrees .

 

[hezzy602]

Re: Adjusting maximum advance timing at high RPM

The Voyager (tbi truck distributor under another name) has 22 degrees of advance so "0" would give you 22 total or as Bondo says try it at 2 for a total of 24. It should be fine, just listen for ping under load. You can set these up at total when reved up to 3000 rpm, just dont hook up the bypass, rev it to 3000 and set it to 24 degrees .

Thanks for the info