Old Style Cutoff on newer ignition

[Sergi]

Hi there,
I have a small problem with the cut off circuit. The fact is that when I bought the boat, the engine harness was missing and the only one I had at hand was a Volvo one. Then, as the swift plate was also missing, I got a used one.

That plate it's the old style, so the switch is all times open, except when going out of gear that shorts to ground.

The engine runs nice, and I find the volvo harness so nice, but it has no cut off provision. So I'm struggling on how to wire that swift interrupt with the Volvo harness. that system uses the newer square coils and thunderbolt ignition with EST module, but only uses one connector to the distributor (from the coil)

I been through some wiring diagrams and answers about that but didn't match my electrical system (newer ign with normally open switch)
Thanks in advance.

 

[alldodge]

Hi there,
I have a small problem with the cut off circuit. The fact is that when I bought the boat, the engine harness was missing and the only one I had at hand was a Volvo one. Then, as the swift plate was also missing, I got a used one.

That plate it's the old style, so the switch is all times open, except when going out of gear that shorts to ground.

The engine runs nice, and I find the volvo harness so nice, but it has no cut off provision. So I'm struggling on how to wire that swift interrupt with the Volvo harness. that system uses the newer square coils and thunderbolt ignition with EST module, but only uses one connector to the distributor (from the coil)

I been through some wiring diagrams and answers about that but didn't match my electrical system (newer ign with normally open switch)
Thanks in advance.

If your trying to wire up a shift interrupter "switch", the you want your switch to be Normally Open (NO) contacts. The switch will be open all the time except when going out of gear. The TB ignition should have two wires, Wht/Red and Wht/Grn. You run another wire from the Wht/Grn wire to one side of the interrupter switch. The other side of the switch goes to ground

 

[midcarolina]

Only thing I can think to do is first remove the grounding terminal block connected to the shift interrupt switch........add a 12v coil normal closed relay, have the shift interrupt energize the relay's coil opening the contact momentarily killing power to coil.

There is of coarse more than one way to go about the wiring.........but you are going to have to add a relay...

 

[achris]

What engine is this? We have no idea if we're dealing with a Thunderbolt IV or V or a 3 litre EST or DIS...

Chris.......

 

[Sergi]

What engine is this? We have no idea if we're dealing with a Thunderbolt IV or V or a 3 litre EST or DIS...

Chris.......

Your right Chris. I'm sorry. This is a 4.3L v6 pre vortec. Don't know what version of the thunderbolt has, but it has the EST module, although it's working without advance control (plugged).
That engine was a recent replacement for the boat I took off, and it's obvious to me that it was a retrofitted EFI engine. It's the last model that had the fake vortec valve covers. when I rebuilt it, IIRC I dated to be from @ 97's 98's. The last with angled intake manifold. It has the balancer.

@AllDodge & @midcarolina, I've got so different approaches there. I must admit that I thought about the relay solution but I was concerned about adding another fail prone element there.
The coil has two connector. The one that bridges the distro has red and black wires, and the other has grey and a really big purple one, but the two of them go to the engine harness. That purple its not going to the distro.

Yesterday I read something really useful here. It explained that the coil receives from the distro a pulsed ground and if I give it a continuous ground it will stall the engine. As easy as locating the negative at the coil.
But I'm wondering about why they replaced that system for the positive cutout. I suppose it may have to do with the charge-discharge duties of the coil. If I supply a continuous ground, the coil may give all it's load until it's voltage stalls. But then it may delay for being at full load.

Perhaps I'm talking nonsense.

 

[alldodge]

Your right Chris. I'm sorry. This is a 4.3L v6 pre vortec. Don't know what version of the thunderbolt has, but it has the EST module, although it's working without advance control (plugged).
That engine was a recent replacement for the boat I took off, and it's obvious to me that it was a retrofitted EFI engine. It's the last model that had the fake vortec valve covers. when I rebuilt it, IIRC I dated to be from @ 97's 98's. The last with angled intake manifold. It has the balancer.

@AllDodge & @midcarolina, I've got so different approaches there. I must admit that I thought about the relay solution but I was concerned about adding another fail prone element there.
The coil has two connector. The one that bridges the distro has red and black wires, and the other has grey and a really big purple one, but the two of them go to the engine harness. That purple its not going to the distro.

Yesterday I read something really useful here. It explained that the coil receives from the distro a pulsed ground and if I give it a continuous ground it will stall the engine. As easy as locating the negative at the coil.
But I'm wondering about why they replaced that system for the positive cutout. I suppose it may have to do with the charge-discharge duties of the coil. If I supply a continuous ground, the coil may give all it's load until it's voltage stalls. But then it may delay for being at full load.

Perhaps I'm talking nonsense.

Sounds like you have the Delco EST distributer setup. Of this is the case you would use the purple wire which is going to the coil and break the connection during shifting out of gear. It would take a Normally Closed (NC) switch and would remove power to the coil when shifting out of gear. The current going to the coil is not much and a relay would not be needed.

 

[midcarolina]

Sounds like you have the Delco EST distributer setup. Of this is the case you would use the purple wire which is going to the coil and break the connection during shifting out of gear. It would take a Normally Closed (NC) switch and would remove power to the coil when shifting out of gear. The current going to the coil is not much and a relay would not be needed.

Since the op has the old style N/O switch is why I recommended adding a relay in earlier post, he is going to have to install a N/C relay to break the power to coil......... or do a search for a normally closed micro switch with the same switching lever to replace the existing one.

 

[alldodge]

Since the op has the old style N/O switch is why I recommended adding a relay in earlier post, he is going to have to install a N/C relay to break the power to coil......... or do a search for a normally closed micro switch with the same switching lever to replace the existing one.

Agree, that's why I said

It would take a Normally Closed (NC) switch

Were all on the same page

 

[Sergi]

The hard part is finding that switch in less than three days.
Will the continuous ground to black wire do while I find this switch?

 

[alldodge]

The hard part is finding that switch in less than three days.
Will the continuous ground to black wire do while I find this switch?

I would say No, a ground would not work. You could either install a relay as midcarolina mentioned, or put in a push button switch which you would press from the helm. The relay is linked below and would also require a connector which could be obtained at most auto parts stores. The hand operated push button switch would have issues because your finger may not be fast enough to switch and disengage before the engine died. You need to break the 12V going to the coil "IF" I you do have an EST distributer

http://www.iboats.com/Merc-Shrouded...9724484--session_id.087994220--view_id.803044

 

[midcarolina]

go to about any auto parts store get a spdt relay it will have 5 terminals.... 2 are for the coil and the other three will be 1 common 1 normally open and 1 normally closed....
you can wire the shift interrupt to energize the relay coil using either the hot or ground to the relay coil ( which ever suites you ) then run your hot for your ignition coil through the normally closed contacts of the relay...........
when the shift interrup closes it energizes the coil of the relay opening the normally closed contacts of the relay..........

I would draw you a diagram but I really stink at drawing...............My artistic skills would likely confuse you.


I almost forgot..... get the relay with male spade terminals makes connecting easier.........

 

[Sergi]

No, please. Do not make any diagrams. :lol:
Don't worry, I may have plenty of relays at the garage. I'm sort of Jeeps fanatic and you know how it goes with them. Always a work on. I think I even have some of them sealed, for diving purposes. :lol:

Thank you very much, midcarolina and AllDodge. I'll tell you how it goes.