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Results 1 to 16 of 16
  1. #1

    Default Mercruiser 4.3 Shifting and Stalling Problem

    I know this is going to sound convoluted, but I will do my best to explain. I have a 1996 Mercruiser 4.3 Gen+ mated to an Alpha One drive. I don't have any serial #'s handy. The ignition is what I believe to be Thunderbolt V, it has the ignition module mounted on the rear of the distributor and no knock sensor. The engine was a supposed reman installed in the spring of last year, due to a freeze and bust.

    I bought the boat last fall at a discount and knew when purchased it had/has a shifting issue. The boat is hard to get from forward to neutral on the water and will skip from reverse straight to forward most of the time. At the time of purchase I assumed it to be a bad lower shift cable, which did not bother me.

    I had the bellows, gimbal bearing, etc. done this spring as well as a new lower shift cable installed. Mechanic says shift cable is installed and adjusted correctly and my issue is something electrical (which is an area he doesn't know much about). After some investigation I found the green/white wire coming from the shift interrupt switch to be unhooked as well as 3 wires from the ignition module (2 green/white's and a red and white). I assume these wires were to go to the ignition sensor mounted within the distributor (red/w & gr/white) and the other green/white to the shift interrupt switch. All of the other wires coming from the module were connected and appear to be right compared to a wiring diagram.

    Upon further investigation I found what appears to be another ignition module mounted on the transom of the boat. It has gray, purple, wh/red & wh/green wire(s). The gray and purple were going to the - and + on the coil respectively and the red/wh and green/white wires were connected to the ignition sensor that is inside the distributor.

    When I unhooked the ignition module mounted on the transom from the ignition sensor, and hooked up the wires that were removed from the other ignition module the boat started and seemed to run fine and the shift interrupt switch worked properly, but the boat will only run until it gets up to operating temperature and then it shuts off, like the ignition has been grounded out. It will then restart and die again until it cools down.

    I have 12v at the coil with the key on, I have 12v from the red and white wire coming from the module with the key on. Unhooking the tach and unhooking the shift interrupt switch seems to make no difference. I know it isn't fuel because the boat runs perfect with the other module hooked up, but there is no wire coming from the module to hook up the shift switch. I ran a jumper from the shift switch to the - side of the coil and it will stall the engine when the switch is manually depressed, but for some reason will not work as it should on the water.

    Is the module mounted on the distributor bad and has someone installed the other module in an attempt to bypass it? If I can use the module that does not have the wire for the shift switch to hook into, how do I wire the shift switch where it will work correctly. I hope this isn't too confusing and I appreciate any advice or help. Thanks

  2. #2
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    5,617

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    Sounds like somebody has kluged a T-bolt IV module to the t-bolt V distributor because the t-bolt V module has developed a thermal issue...as you have found out, it doesn't work very well as done.

    I'd say you can verify the module (V version) fails when it is hot and either get another one, switch over to a new distributor, or fix the kluge to make the IV module work with the V distributor. The risk is you don't know if all the shift interrupter parts are correct or whether they were kluged too. Another factor is you aren't likely to find anybody that will work on it ... the interrupter just kills the ignition when the cable tension activates the switch...

  3. #3
    Join Date
    Jul 2008
    Location
    Northboro, Ma, USA
    Posts
    3,522

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    Here is the correct wiring.........maybe the "other" module is the knock sensor???

    if not see if this helps.

  4. #4

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    Welcome aboard !

    I think all you want to do is go boating, not fool around with the engine everyday.

    The shift int, micro switch gets hooked up one wire to a ground ( look right behind the engine there is the stud for it ) the other wire to the neg side of the dist. that simple understand ?

    Go to ebay look up hei dist, all in one unit with the coil built in for a 4.3l. You want the manual advance model not vacuum advance, understand ?

    Remove and install the hei unit, one wire in one wire out one wire to the tach. and hook the wire to the micro to the neg side. Understand so far.

    Go boating and when you get back and everything is working good you can make a anchor out of the t-bolt stuff.

    Side note you want the lowest rpm on a warm engine in gear at idle. 600-650 the lower the better to shift.

    Also the throttle handle might have broken off the tab that stops you at neutral, you might need a new one.

    Good luck post back !

  5. #5
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    7,442

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    I would tend to agree that the "other" module may be a rev-limitter.
    Look at the p/n, and do a search.


    Also, keep in mind that a final Shift Interrupt adjustment must be done while the boat is in the water so that prop thrust becomes part of the equation.
    No prop thrust, and the adjustment cannot be made accurately.



    .
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  6. #6
    Join Date
    Jun 2006
    Location
    Spotswood, NJ, USA
    Posts
    2,753

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    If this is fuel inj with a ecm the TBIV items wont work. TB IV used a ground, TB V uses 12v applied.

  7. #7
    Join Date
    Jun 2006
    Location
    Spotswood, NJ, USA
    Posts
    2,753

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    http://www.boatfix.com/merc/Servmanl/18/18E4R2.PDF anything look familiar. Could they have replaced the motor with one that went to a Bravo drive? They dont use a interupter circuit.

  8. #8

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    The setup I have matches pg. 5 of the boatfix document above, Alpha T-bolt V w/out knock sensor, and matches the diagram on up the thread, minus the knock sensor. The module mounted on the transom appears to be a T-bolt IV module (it looks like Merc part # 807829-1), but I am not sure this is the same exact one as I haven't verified the part number if it matters.

    My guess is as someone stated above, the t-bolt V module has an issue when the boat gets to operating temperature and someone has stuck the other module in there to get it to run. The boat will run great with the t-bolt iv module attached, but the shift switch will not work on the water, although it works when manually depressed. This is with the green/white from the switch jumped over the - side of the coil.

    When cool the t-bolt V module seems to be fine and the interrupter switch stumbles the engine as it should, but almost as soon as the boat hits 150-160 degrees its like somebody turned the lights off and she shuts down. I'm assuming the module has to have a fault due to the fact it runs fine with the other one hooked up. Thanks for the advice on the distributor, unless something pops up that I am missing here that is probably the route I will go. Is the Delco Voyager EST kit the best choice for this engine? Thanks again. Also this is a carb engine to clarify the question in a post above.

  9. #9
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
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    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    Quote Originally Posted by Lego View Post
    1. My guess is as someone stated above, the t-bolt V module has an issue when the boat gets to operating temperature and someone has stuck the other module in there to get it to run. The boat will run great with the t-bolt iv module attached, but the shift switch will not work on the water, although it works when manually depressed. This is with the green/white from the switch jumped over the - side of the coil.


    2. Is the Delco Voyager EST kit the best choice for this engine?
    1. No offense, but do you understand the purpose of the SI (shift interrupt) regarding Dog Clutch gear engagement?

      The reason for the boat being in the water, is to create the shift cable resistance (while trying to separate the Dog Teeth against prop thrust), of which operates the micro switch cam lever arm.
      Operating the micro switch by hand will not tell you much, other than that the switch itself is working.

    2. It would be a good choice over that of the Merc TB system, IMO.
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  10. #10

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    Quote Originally Posted by RicardoMarine View Post
    1. No offense, but do you understand the purpose of the SI (shift interrupt) regarding Dog Clutch gear engagement?

      The reason for the boat being in the water, is to create the shift cable resistance (while trying to separate the Dog Teeth against prop thrust), of which operates the micro switch cam lever arm.
      Operating the micro switch by hand will not tell you much, other than that the switch itself is working.
    2. It would be a good choice over that of the Merc TB system, IMO.
    Just to clarify what I am trying to say about the shift switch, with the T-bolt V module connected the boat shifts fine while in the water with the switch wired into the module as it should be, it just won't run very long. With the T-bolt IV module connected and the shift switch jumpered to the - side of the coil the boat will not or will with great difficulty shift from gear into neutral while on the water, although I can depress the switch manually and it does stumble the engine. So the switch in theory is working while wired this way but for some reason not working while shifting. Not exactly sure why it will work when connected to one module and will work manually (only) when connected to the other.

  11. #11
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    Mar 2009
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    Portland, Oregon,
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    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    Quote Originally Posted by Lego View Post
    With the T-bolt IV module connected and the shift switch jumpered to the - side of the coil the boat will not or will with great difficulty shift from gear into neutral while on the water, although I can depress the switch manually and it does stumble the engine. So the switch in theory is working while wired this way but for some reason not working while shifting. Not exactly sure why it will work when connected to one module and will work manually (only) when connected to the other.
    That is rather strange.
    It would appear to be logical that if the micro switch does indeed stumble the ignition, that the micro switch adjustment (as per the cam lever arm) is not correct.

    Under normal conditions (with the SI working correctly), shifts are to be made quickly and decisively as to not completely kill the ignition.
    All of this takes place within a micro-second or two.... and the Dog Clutch teeth are now able to disengage with ease.

    A slow shift will stumble the ignition for too long a duration.

    Again, the resistance of the Dog Teeth (via the cable) is what operates the cam lever arm. Actually, it's the outer cable jacket that operates the cam lever.

    Basically, the SI will either stumble the ignition, or it will not stumble the ignition.
    Usually an adjustment between the micro switch arm and the cam lever will correct this.

    I'm not sure what else to suggest.




    .
    Last edited by RicardoMarine; 06-26-2013 at 11:53 AM.
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  12. #12
    Join Date
    Jul 2008
    Location
    Northboro, Ma, USA
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    3,522

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    Most likely with the interuptor switch wired to one module and then jumped to the other location it may not be seeing a clean short to ground....

    What ever the case either replace the correct module or the whole ignition assembly with a one piece unit as suggested........

  13. #13
    Join Date
    Jul 2008
    Location
    Northboro, Ma, USA
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    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    The reality is you can eliminate the TB V unit if it is bad, Wire in the TB IV Unit.

    They do the same thing just packaged differently...........See if that works and solves all problems...
    Last edited by kghost; 06-26-2013 at 02:07 PM.

  14. #14

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    Quote Originally Posted by kghost View Post
    The reality is you can eliminate the TB V unit if it is bad, Wire in the TB IV Unit.

    They do the same thing just packaged differently...........See if that works and solves all problems...
    I may have found a known good TB V module here locally that a guy will let me swap into my boat to see if that is the problem. If I can't do that, regarding using the TV IV module, would the green and white wire from the shift switch simply splice into the green and white connection (where the module connects to the ignition sensor at the distributor). The TB V module has a dedicated wire for this, the TB IV module does not. Thanks again for all the help.

  15. #15
    Join Date
    Jul 2008
    Location
    Northboro, Ma, USA
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    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    The TB IV green w white was connected at the distr to a screw.
    So the second green w white was attached at the stud and then it went
    To the interuptor switch.
    The TBV as you said had a dedicated green w white wire.
    So when connecting the green w white wire you would need to
    splice a length of green w white to that connection.

    Black is ground. Purple goes to coil +. Grey goes to coil -
    White w red to dist white w red and white w green goes to
    dist white w green and shift interupter switch.

  16. #16

    Default Re: Mercruiser 4.3 Shifting and Stalling Problem

    Ok Lego i wish you luck in all your endeavors.

    Let us know when you get tired of messing with the boat and if you have questions about the new system you buy.

    Delco is a good choice. Manual advance not vacuum.

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