TOPIC: '67 500 Thunderbolt with no instrumentation

I've got a '67 500 Thunderbolt with no instrumentation. I believe the controls are a later model than the engine. There are wires coming out of the control- Brown, black, purple, tan/blue stripe, and gray. The are not connected to anything. There is a harness that is plugged into the motor and everything works fine.

Can I get a tach and temp on this motor? Are the wires from the control of any use to me in this? I've included photos for reference.

Thank you.

Hi,
In 1967, there were manual, starter, and electric model Merc 500s. Both the starter and electric models are electric starting, but the starter models do not have a charging system and in 1967 used a magneto ignition. If you have an electric model which has breaker-less CD ignition, the tachometer installation will be much easier. I am unsure if the adaptor harness your motor appears to be equipped with (to allow use of the very recent remote control box) allows for the tachometer feed with the new control. This can be checked simply by checking the gray wire at the remote control for connection (using a VOA meter) with the brown wire originally attached to the (4) terminal side of the ignition module inside the motor's cowlings. If so, the gray wire is the tachometer sender wire. The black is ground, and the purple is 12 volts when the ignition key is in the "on" position. The easiest would be a modern tachometer which reads a 12 pole alternator charging system. The gray, purple, and black are the three connections needed for operation at the tachometer. Inside the motor cowlings, the brown wire should be removed from the (4) terminal side of the ignition module, and then connected at the charging system rectifier to either of the yellow wires (do not connect to the red wire terminal). This will yield a functioning tachometer if the charging system is working properly.

Regards,
Joe
www.fergusonpoolemarine.com

When you say, "There are wires coming out of the control- Brown, black, purple, tan/blue stripe, and gray."
Don't mistake this 'brown' wire for the brown wire Joe is referencing.
I would have to hike out to the shop to positively identify just what 'your' brown wire is for (I think it is actually tan) and I can't make the hike right now.
The tan/blue is the engine temp wire for later model motors that your controller/harness originally came with and there is no place for this wire to go on your 500.
The purple is accessory 12v when the key is 'ON' and can be used for more than on motor related instrument on the dash.
Because of the vsriety of ignitions used on the 500 a few pictures would be helpful.
Bear in mind that this forum can only handle relatively small pictures (850X600+/-) but I have seen very large pixs post - just don't know the secret.
Thom

Ferguson_Poole wrote:

Hi,
In 1967, there were manual, starter, and electric model Merc 500s. Both the starter and electric models are electric starting, but the starter models do not have a charging system and in 1967 used a magneto ignition. If you have an electric model which has breaker-less CD ignition, the tachometer installation will be much easier. I am unsure if the adaptor harness your motor appears to be equipped with (to allow use of the very recent remote control box) allows for the tachometer feed with the new control. This can be checked simply by checking the gray wire at the remote control for connection (using a VOA meter) with the brown wire originally attached to the (4) terminal side of the ignition module inside the motor's cowlings. If so, the gray wire is the tachometer sender wire. The black is ground, and the purple is 12 volts when the ignition key is in the "on" position. The easiest would be a modern tachometer which reads a 12 pole alternator charging system. The gray, purple, and black are the three connections needed for operation at the tachometer. Inside the motor cowlings, the brown wire should be removed from the (4) terminal side of the ignition module, and then connected at the charging system rectifier to either of the yellow wires (do not connect to the red wire terminal). This will yield a functioning tachometer if the charging system is working properly.

Regards,
Joe
www.fergusonpoolemarine.com

Thank you all for your replies. Perhaps the attached imaged from under the cowel will help determine what type of ignition I have and exatly which wires to tap. The images are: Cowel plate, port side, port side top, port side bottom, and starboard side

Your control appears to have a trim/tilt switch (rocker switch) in the handle. If so, the wires under the key are probably for the switch.

Hi,
I would suggest that you call me, or e-mail a contact phone number. I believe that I can talk you through this more accurately, and surely faster than trying to write down my thoughts.

Regards,
Joe
(770) 597-5992 Cell (free minutes after 9 PM Eastern)
This email address is being protected from spambots. You need JavaScript enabled to view it.
www.fergusonpoolemarine.com

I will do that soon. Meanwhile than you to everyone, you are a great help!