1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or what?

[rhillman75]

1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or what?

About 3 weeks ago I took it to my marina technician to have some late summer maintence done to it and he "swears" up and down that it is a Thunderbolt IV ignition that he put into "base timing" by grounding the purple/white wire (the wire was in the main harness with a female bullet connector) just to the left side of the MerCarb 2 barrel by the choke. My distributor does have the module mounted on the side and the arrestor cover does clearly state "Mercruiser 4.3LX Gen+". Does he really know or has he advanced or retarded the timing by 10 degrees? We have been experiencing rough idle, dieseling, and hard starting after almost EVERYTHING has been replaced. I know Don S. replied sometime ago with a picture of what looked to be exactly like my distributor but this marina is one of the BEST Mercury/Mercruiser authorized centers available within driving distance... so I do not know if I should doubt him or not. My engine specs are below in my profile.

 

[StevNimrod]

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

If it's got the shunt, I believe it is a TB V.

But...

If somebody has ever worked on it using the Seloc manual (which should be kept in the bathroom, for emergencies), then the wrong plugs might be in it. My neighbor has a 1997 4.3 and Seloc called out the wrong plugs (reach was about 1/4" shorter than the correct plug) - he had all the same issues you describe. What happens is that somebody puts in the wrong plugs, and as tune-ups are done, people replace plugs by matching up the old ones. He had many "certified" Mercruiser mechanics work on it and nobody caught it. It might be worth your pulling a plug and telling us what it is.

 

[John_S]

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

The grounding of the purple/white wire would indicate Thunderbolt V and that is what is suppose to be in a '96. I believe base mode initial timing is 10 degrees BTDC.

 

[TilliamWe]

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Does your arrestor cover also say "Digital Ignition"?

 

[Don S]

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

There wouldn't be a purple/white wire in the harness for him to ground if it was a TB4 igniiton.

 

[rhillman75]

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Okay... let's look at in this manner... I have seen first hand this purple/white wire with the bullet connector. I have also held it in my fingers with a light to further the colors are accurate and they are. If for some unknown reason the previous owner did change or replace the cover that states (Mercruiser 4.3LX Gen + Thunderbolt Ignition) would there be another way to find what the engine TRULY came with. I have never noticed if it said IV or not so I will try to verify that this evening. I know the marina said that when I brought it in in the spring having some issues of the dieseling and the idling he stated at that time it needed to be in base timing and that whoever had adjusted it before had it at 10 degrees off where it should have been. I am going to take pictures of the distributor hopefully tonight and get them posted. This is really wearing me thin... I just want to know what the hell it is and if it is set up wrong it could be the entire problem all along.

 

[Don S]

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Your engine serial number (0F821387) uses ignition control module PN 807829T1 that is for a TB5 ignition system, the parts program doesn't even list the TB4 as an option.
So, if you have a TB4, then somebody changed it and modified the wiring harness for the TB4, because there is no purple white wire on a TB4 ignition system. That purple/white wire comes out of the ignition module.

 

[John_S]

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

and a Thunderbolt IV module will not fit the thunderbolt V connector. Show us a clear picture, and we can make it 100% certain. Hate to see you loose any more sleep over this.

 

[rhillman75]

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

and a Thunderbolt IV module will not fit the thunderbolt V connector. Show us a clear picture, and we can make it 100% certain. Hate to see you loose any more sleep over this.

I should have pictures posted this evening around 9-10 p.m. Indiana time. Hopefully you guys have a your late night beer/coffee while you can figure this one out. At this point my marina tech is pretty pissed at me about questioning him and has kindly asked me to take my business elsewhere. Whatever happened to the days when you could ask for explanations considering I have paid him quite well over the years!

 

[Don S]

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

Re: 1996 Mercruiser 4.3LX "base timing" question! Is my marina technician wrong or w

At this point my marina tech is pretty pissed at me about questioning him and has kindly asked me to take my business elsewhere.

Basically, it doesn't make one bit of difference what he calls it, if he wants to call it a TB4, let him. As long as he puts it in base timing mode like you would a TB5, who cares what he calls it.
Your problem is this. If he doesn't know that a TB4 ignition doesn't need to be put into base timing mode, what else is he just guessing at?
I assume he is NOT a certified Mercruiser dealer.

 

[rhillman75]

Houston... I think we have SOLVED the issue! Pictures included!

Houston... I think we have SOLVED the issue! Pictures included!

This thread is for Bondo-o, Don S, and imported_john. I finally got a chance to get my hands back on the distributor tonight to take pictures of it as well as the motor cover. I do not know if this is a T4 or T5 ignition so i will let you deliberate from here! Pictures are included of everything I thought you needed to help me solve this rahter long dilemma. All I need to know is if it is T4 or T5, should the wire be grounded (purple/white), does it need to be grounded to adjust all 3 (3 meaning= timing, idle mixture, idle speed). I also need to know if the idle needs adjusted in the water in forward detent. I know its alot to ask for but I am so sick of reading this Clymer manual and with all the members that have chimed in with yes and no concerning the T4/T5 question...I would like to hear it from you guys. Thanks for ALL your help!

 

[Don S]

Re: Houston... I think we have SOLVED the issue! Pictures included!

Re: Houston... I think we have SOLVED the issue! Pictures included!

I merged the two posts together, as this last one is nothing more than a continuation of the original post.

It is a TB5 distributor, and stop using knee pads (aka clymers) as service manuals.
Download the correct manual free here. http://www.4shared.com/document/TcnPb3wU/Service_Manual_18.html

The drive manual is here http://www.4shared.com/document/dPQUcyn_/Service_Manual_14.html

Look in the engine manual at the ignition section. Then you will know what you have.

 

[John_S]

Re: Houston... I think we have SOLVED the issue! Pictures included!

Re: Houston... I think we have SOLVED the issue! Pictures included!

Yes, it is T5,

Yes, it needs to be in base mode, for idle speed, idle mixture, and initial timing. The SM Don linked to should provide all the details you need.

 

[rhillman75]

Re: Houston... I think we have SOLVED the issue! Pictures included!

Re: Houston... I think we have SOLVED the issue! Pictures included!

I am looking at the service manual and on page 5B-10 (final idle speed & mixture setting) it does not state whether to put it into "base" timing. I have scrolled up and down and read and re-read... and unless it's hidden in there I do NOT see where it states to put it into "base" timing to adjust the idle speed and idle mixture. I don't know... I may be blind but I do not see where it states to ground ANYTHING!

 

[Don S]

Re: Houston... I think we have SOLVED the issue! Pictures included!

Re: Houston... I think we have SOLVED the issue! Pictures included!

Try page 4B-10

The manual if for TB4 and TB5.

You have to understand, these manuals were meant for Mercruiser trained techs that read bulletins and get the proper training.
Your shop would have received this service bulletin back in 94. Then, you would remember that for the next XX number of years.
It's still going on today on the TB5.

 

[John_S]

Re: Houston... I think we have SOLVED the issue! Pictures included!

Re: Houston... I think we have SOLVED the issue! Pictures included!

I'd be curious to know if your base timing was off. It sounded like your mechanic was doing the correct procedure, just calling T4 instead of T5.

 

[rhillman75]

Re: Houston... I think we have SOLVED the issue! Pictures included!

Re: Houston... I think we have SOLVED the issue! Pictures included!

I'd be curious to know if your base timing was off. It sounded like your mechanic was doing the correct procedure, just calling T4 instead of T5.

Now I kind of feel like a jackass... considering the timing was dead on! Now I am just trying to figure out the idle rpm as I am thinking the throttle cable is shot. My wife and I took it out and ran it until it got to normal tep. Then I shut it off (dieseled for about 2 seconds) considering it was idling about 1,000 rpm. I grounded the negative terminal on the bat and sent the other end of the wire to the purple/white wire. I started it and let it run about 15-20 seconds and just by watching the the throttle cable I notice that if you engage the nuetral button and got the rpms up to about 2,000 rpm then brought it back to neutral... the cable was very slow at bringing the arm back to idle position in fact I had to wiggle it to get the rpms down to get the idle screw to hit the stop. Then I pulled the throttle cable off at the adjustment end and turned it away from the carb to take some slop out but it did not produce that much of an improvement. I noticed the only way to get the idle back down to 700 rpm was to actually wiggle it after the commander was brought back to neutral position. Either way... the only way to really get the idle back down naturally is to assist the cable by wiggling it a tad while its connected or adjust the barrel away from the carb but that seems to put negative tension on the cable. Right now the line up points are even at the carb and about 1/4 pass the attachment point on the motor. With it in this way it is easier to bring the motor down but a pain in the *** to get it to restart when cold. Sound like a new cable is coming?

 

[John_S]

Re: Houston... I think we have SOLVED the issue! Pictures included!

Re: Houston... I think we have SOLVED the issue! Pictures included!

Now I kind of feel like a jackass... considering the timing was dead on! Now I am just trying to figure out the idle rpm as I am thinking the throttle cable is shot. My wife and I took it out and ran it until it got to normal tep. Then I shut it off (dieseled for about 2 seconds) considering it was idling about 1,000 rpm. I grounded the negative terminal on the bat and sent the other end of the wire to the purple/white wire. I started it and let it run about 15-20 seconds and just by watching the the throttle cable I notice that if you engage the nuetral button and got the rpms up to about 2,000 rpm then brought it back to neutral... the cable was very slow at bringing the arm back to idle position in fact I had to wiggle it to get the rpms down to get the idle screw to hit the stop. Then I pulled the throttle cable off at the adjustment end and turned it away from the carb to take some slop out but it did not produce that much of an improvement. I noticed the only way to get the idle back down to 700 rpm was to actually wiggle it after the commander was brought back to neutral position. Either way... the only way to really get the idle back down naturally is to assist the cable by wiggling it a tad while its connected or adjust the barrel away from the carb but that seems to put negative tension on the cable. Right now the line up points are even at the carb and about 1/4 pass the attachment point on the motor. With it in this way it is easier to bring the motor down but a pain in the *** to get it to restart when cold. Sound like a new cable is coming?

I believe the idle mixture and idle speed are set with cable disconnected, but check your specific service manual.

Make sure thottle shaft is not worn/binding.

Throttle cable should have some spring preload in it. An old style throttle spring attached to throttle lever, would probably help.

Is your choke set-up correctly for your cold starts?

 

[rhillman75]

Re: Houston... I think we have SOLVED the issue! Pictures included!

Re: Houston... I think we have SOLVED the issue! Pictures included!

I believe the idle mixture and idle speed are set with cable disconnected, but check your specific service manual.

Make sure thottle shaft is not worn/binding.

Throttle cable should have some spring preload in it. An old style throttle spring attached to throttle lever, would probably help.

Is your choke set-up correctly for your cold starts?

So my next question (concerning the throttle cable adjustment) is... if I have the cable attached to the carb and then I pull the cable barrel toward the carb to "pre-load" then line it up and put it in the bracket, or is it... it if I have the cable attached to the carb and then I push the cable barrel away from the carb to "pre-load" then line it up and put it in the bracket? If it is pulled toward the carb and line it up with the bracket and I push the throttle commander to the detent position forward the motor starts and goes to about 3,500 rpm (that's bad to me), but if I push it away from the carb and go about 1/4 inch past the bracket then I hook it up and start the motor... it idles somewhat fine, but it takes a little time (about 20 seconds) for the idle to come down while the cable "relaxes". I think the spring in the cable is TOAST!