How to make a timing shunt?

[TimayZ]

I found this in a search but the pic used as a diagram was no longer visable.
Does anyone know how to make one So I can set my base timing withouth buying one? Have a diagram or a good explination on how to do it?
What I gather so far is jumper the two white wires and disconnect something. Can you help make this a little more clear?
I have a new merc 4.3l with the Denso box.
Thanks!

 

[Don S]

Re: How to make a timing shunt?

I have a new merc 4.3l with the Denso box.

What they H*** is a Denso box?

Got a year, better yet a serial number for this Merc 4.3L?

 

[TimayZ]

Re: How to make a timing shunt?

2006 4.3l mercruiser OW388974. Denso is the name brand on the ignition box sorry.
I know I have warranty.... It's just not worth it to me to drive an hour+ to let someone work on it that I'm sure will not do a better job them myself.(wish I knew a merc mechanic I could trus around here) It has had "run on" since day 1. I just installed the NGK-TR6 plugs(one range colder) and trying to set the timing before I take it out and try it. Figure'd I'd give it a try. With 0 hous on it I doubt it's carboned up. Fuel is 93 octane. Idle set at 650 once it settles in. It still run's on after you let it idle for a while. Every now and again will will not "run on" if you let it idle for literally 2-3 min. It backfires a little once and a while when you floor it to pull up a skier. I think the timing is just off. Boat now has 15 hours on it. The backfiring just started and the hesitation started last weekend. Runs great for the most part, fires right up everytime with just a turn of the key. Bilg blower it always on when i'm not moving.
It's right on 10* before TDC with everything hooked up. I just wonder if it will be off if shunted. (say it happens to be advanced) so then when I nail it to take off the timing curve is off so it bacfires or hesitates here and there. Sounds like a plan to me atleast. HAhah

 

[Silvertip]

Re: How to make a timing shunt?

This is a warranty issue for the dealer. If the dealer sees that you've been screwing with it you can kiss the warranty good by. Put the original plugs back in and make the trip.

 

[Don S]

Re: How to make a timing shunt?

You have a Thunderbolt V ignition system, that "Denso box" is called an ignition module.
There really isn't any shunt you need to set it into base timing, what you do need is a service manual that explains how to set it up. IF you plan on doing your own maintenance, you better get an OEM manual for your engine.
Your problem sounds more like a lean idle mixture than a timing problem.
Here is the process from the merc manual you need.

 

[Haut Medoc]

Re: How to make a timing shunt?

You would be insane not to take it back to the dealer & let them fix it!
I would follow Silvertips advice, even if Don S. is right....
I would not risk voiding the warranty!......JK

 

[cobra 3.0]

Re: How to make a timing shunt?

93 octane? Was it timed for 93 octane? I don't think so. Going down to a lower octane may improve your situation.

 

[bruceb58]

Re: How to make a timing shunt?

Why would you say that? Lower octane would make matters much worse.

One more thing...you don't need to time for higher octane anymore. The knock sensor takes care of that for you which wouldn't be in effect at idle anyway.

93 octane? Was it timed for 93 octane? I don't think so. Going down to a lower octane may improve your situation.

 

[TimayZ]

Re: How to make a timing shunt?

93 octane burns slower and cooler. That's why I tried it out before I did anything else. It made no change. And the NGK TR^ plugs I installed are mercruiser recommended.
Well I grounded the wire and the base timing was @ 8*BTDC That's only 2* off. So I set it for 10 as recommended. That done, plugs swapped AND the throttle cable adjusted. (It was a little lose and would not let the idle screw bottom out sometimes.)
We will see what the change was.
Thanks for the help!!! I needed some specifics as to how to get it into base timing mode. Thanks DonS. Way different then the last 4.3l timing adjustment in my old 1992 Bravada. LOL That I just unplugged a connector under the passenger seat.

I know most of you wont understand about the warranty and not taking a day off work to drive 60miles to the dealer. I'm a mechanic in the Air Force and on my own 10 sec LS1 Drag car, fully confident I can do any of the needed adjustments.
I am also very anal when it's my equipment, the thought of some back woods mechanic in arkansas working on my SeaRay turns my stomach. I know he wouldn't be as careful as I would.(even if he did happen to be good) I never take anything I own into a dealer unless it major work I can not perform. I have also never been denied ANY warranty work on anything I have ever owned because I did my own minor maintenance. I have never even been asked for "proof" I did the maint. Al-tho I do keep a history of it all with receipts.

 

[kbetts]

Re: How to make a timing shunt?

I agree with Silvertip, take it back to the dealer. Messing with the timing doesn't sound like "minor maintenance" when it's an 06.

 

[bjcsc]

Re: How to make a timing shunt?

TimayZ: Something seems funny to me. If you were reading 10&deg without the shunt and 8&deg with it, and now with the change, you have 10&deg shunted and 12&deg without it at idle, correct? The reason this seems odd, and I could be way off, is that for my ignition the base timing with the shunt is 6&deg . Without the shunt it is (and is supposed to be) 11&deg at idle, i.e. +5. Does your manual give you check points for your advance? Eg. for me I should (and do) see 17&deg &plusmn 1&deg at 1600rpm. Just seems odd...

 

[TimayZ]

Re: How to make a timing shunt?

You are correct.
I am in the process of getting a manual. Is your ignition the same setup as mine?
I set it to 10 on the base timing as recommended. (again I don't have a detailed service manual as of yet) You are right it was at 8. Are you sure your setup is the same as mine? If your talking about thesetup in your sig.

 

[DHPMARINE]

Re: How to make a timing shunt?

Actually,since you have a new boat,I would put it back to stock and let the dealer handle it.You did buy the boat 60 miles from the dealer. So the trip is yours.Also tell him you did this.

I realize you didn't list what motor you have,exactly,but if it has a carburetor,you might only need a cable adjustment.

DHP

 

[Don S]

Re: How to make a timing shunt?

Come on guys, Setting the timing and adjusting the carb is not that big a deal for anyone that understands how engines and ignition systems work. There are people on this board that have to be shown where the distributor or carb is so they can adjust the timing and mixture.
I gave him the details on setting the timing propely. It was a full page out of the Merc service manual. The flame arrestor has a decal on it that gives the proper spec. Which is 10° BTDC at idle rpm (650rpm) as he mentioned he set it.
The process of putting it in base timing mode when adjusting the carb and idle speed is to prevent the module from changing the timing during the adjustment process.
If he has the idle mixture and speed set and the timing is correct and everything works, there is no reason what-so-ever that a dealer would void his warrany.
I see his point about not wanting to make the 60 mile (one way) trip twice just to get the timing checked and reset.

DHP, he gave his serial number. For me that was all I needed to see what he had, and I did ask for his SN.

 

[TimayZ]

Re: How to make a timing shunt?

I'm not going to repeat myself over and over.
I told you all what my feelings were on the warranty issue. I have been nice and respected you all over and over as you tell me to take it in. Thanks for the advice. Now please respect me back and let it be. You not going to get me to just drop it and take it in untill I know I tried what I wanted to try. If your a mechanic at all you know the next guy who cares about his eqipment and has set timing before, can do this procedure.
I asked a question, got an answer for it and thanked Don S.
All is well! Dont worry be happy. LOL

 

[bjcsc]

Re: How to make a timing shunt?

TimayZ: I doubt my ignition is the same as yours, but I would think the advance would be similar so I was just asking. I don't know any specifics about your ignition, but I have experienced module failures on both my boat and on my Jeep (HEI). On my boat ignition, the failure was no advance and on my Jeep it was weird/erratic advance. Maybe Don S. has access to the check points for your specific ignition. I only brought it up because the module function is something else you can check pretty easily before you hit the water. BTW, I would have checked/reset the timing myself, too...

 

[bruceb58]

Re: How to make a timing shunt?

Going back to one of your original problems...the hesitation and backfiring you get(backfire through the carb I assume) is a lean condition. Although the accelerator pump is supposed to help, I have found just jamming the throttle forward causes to much of a lean condition even for the accelerator pump to handle.

I don't think this is a timing issue at all. You are right in the ballpark timing wise.

Letting it idle for 2-3 min without run on is your clue...it is temp related. You can lower the cylinder temp slightly by richening up your idle a bit and see how that works.

What do the plugs look like after running? How about after idling? Do they all seem to be pretty normal color?

 

[TimayZ]

Re: How to make a timing shunt?

The plugs looked great when I swapped them however, I have not pulled a plug out on the water right after use. I know that is the only way to see if i'm lean or not for sure. Or install an o2 sensor/EGT guage and I dont see myself doing that. I agree 2* does not seem like anywhere near enough to cause a backfire problem. (yes through the carb) It's rare the boat does this however I dont see it as "normal". I also think they are both the same problem. The plugs must be getting to hot and glowing. I hope to have already solved this problem by #1 getting the colder plugs #3 getting the idle cable set so it can idle down to 650 all the time now v/s every once and a while and #3 the couple * of timing will help some.
It does run a little warm on eng temp from what I see on everyone else's boat at around 180*. But then again most cars run 180-210 and they dont have run-on problems...Also the warmer the engine the better for combustion. Unless your not feeding it enough fuel of course.
Ill be out of town this weekend so it will be next week sometime before I can get to it. Hopefully by then ill have a detailed manual and some time to take the boat out to do some testing. I just want to make sure I didnt fix it before I turn up the fuel.
Thanks for all the help.