Marine Wiring Articles on...Tachometer
Thank you for all of the boat wiring expertise that you provide.
Here’s my issue:
The dash mounted tachometer (see photo) needle(s) wander (drifts) around. I read that his could be caused by a bad ground. It could also be from poor signal connection.
Do you have any information on how the instrument is wired to the signal source. And what is the signal source?
On EFI engines, the tach signal comes from ECM. On carb engines, the signal comes from the distributor. Both use a gray wire and it runs through the boat’s engine harness, through the main engine connector, and up to your boat’s instrument panel. Some boat builders use a gray/red as the second engine tach signal to help reduce confusion. I would check all connection points of the gray tach signal wire for each engine.
Your best bet to help cure the drift, is to run a new, clean ground wire from the tachometer back to your ground bus or engine negative stud. You can remove the existing ground (black) wire on the back of your gauge and tie it up to prevent it from an accidental short.
Hope this helps,
I have a question regarding boat wiring from an engine to the instrument panel.
I have a 1985 Ebbtide Catalina with a Mercuiser 350. It blew up on me, so I pulled it and found a new (08) Volvo 5.7 GI to put back in its place. I got a crazy good deal on the motor so I couldn’t turn it down.
Now the problem is that I need to connect into the 14 pin plug and 2 other smaller ones that I guess communicate to the gauges. I have all of the gauges from the boat that the new motor came out of so I was wondering if the Engine to Instrument panel wiring kit would work for me? I am going to redo the dash with the new gauges anyway. The only one that is missing is the tilt/trim.
The boat the motor/gauges/thrust controller came out of was a ’08 Glastron Cuddy Cabin, (not sure about the length).
I really appreciate any kind of help I can get on this. I really want to get out to the lake this year!
Your engine harness boat wiring colors are
- Black – Ground
- Red/purple – Ignition power in
- Purple – Ignition power to engine
- Yellow/red – engine start
- Tan – water temperature
- Gray – tachometer
- Lt blue – oil pressure
- Pink – fuel sender
- Brown/white – trim position
- Red/white – trim power in
- Blue/white – trim up
- Green/white – trim down
Also, here is a list of the standard boat wiring colors used on the rest of your boat.
Hope this helps,
I am currently beginning my first boat wiring project, a total rewire of a small Owens cruiser from the late ’60s.
Here’s my problem:
The old wiring runs behind the original paneling and headliner. I could try dismantling everything to remove and replace the wires, but am concerned about damaging any of the woodwork. It’s old. It’s gorgeous. It would be a bitch to replace.
I don’t mind leaving the old wiring in place and just running a new harness, but that still leaves the problem of installing the new wires without causing any damage.
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My name is Thomas.
I just picked up a set of Lenco trim tabs and the directions say to connect the retractor wire (orange) to the engine tach signal. On my boat that’s the negative side of the ignition coil.
Is this what they mean? Or does it go somewhere else?
If you want to use the retractor function of your Lenco tabs, you will need to connect the orange wire to the negative side of your coil.
I believe that the retractor function of the Lenco tabs will work by simple connecting the orange wire to your switched ignition wire, but this might explain why Lenco doesn’t seem to publish this anymore.
Thank you for all your help. I found that info.
By the by, following the suggestion on your web site, I got a boat wiring harness and a marine electrical panel from EzAcDc. It all works perfectly!
The EzAcDc boat wiring was easy to install and modify to my particular needs. I set it up independant of the ignition so the panel is live so long as at least one of the batteries is switched on.
However I am thinking that I want another automatic bilge pump, my third, unfused & wired direct – bypassing the main switch so it will pump any time and unattended while I’m ashore goofing off.
Any thoughts on that?
Thanks again for this awesome resorce!
You will want to have circuit protection for your third pump. All new bilge pumps have their fuse size stamped on them.
To wire this new pump correctly, install your fuse/breaker as close as possible to the battery. You will have two wires leaving your fuse. One goes directly to your auto float switch and the other to your manual bilge pump switch. The wires leaving your float switch and your manual switch are connected together (usually near the bilge pump) to provide two different ways to turn on the pump. Attach your bilge pump ground to your battery negative or a ground buss.
Sadly your trim tab link didn’t work. Pitty, as I like to know all I can about any given thing.
So conecting to the tach wont disrupt the tach reading? Is one way better than the other?
Sorry about that.
As for the trim tab installation, connecting the retractor wire to the coil will not disrupt the tach reading.
Have a great day,
I have a question in regards to wiring my boat tachometer. I have a 1973 135Hp Johnson outboard V4 on a 1970 Glastron and the tachometer is not working simply because it’s not connected to the rest of the boat wiring.
So where do I start..? I’ll run all new wires, but to what? And how many wire leads will I need? Do I wire it into the throttle box, if so, to the ignition switch and how or do I have to run a set of wires to the motor directly?
All the required wires should already be at your ignition switch/throttle box.
- Purple – Switched power from Key switch – Connect to B+ on your tachometer
- Gray – Tach signal – Connect to the S on your tachometer
- Black – Gauge ground – connect to the (-) on your tachometer
Hope this helps,
Thank you kindly; you’re really prompt and it’s appreciated. I can’t wait to get back under the dash and look for those contacts on the tach.
Funny, I just had to replace my throttle cables last weekend (it snapped just past the no wake zone; not good, however we couldn’t dare tell our 4 and 5 year old boys that the party was over. They were so excited to be on the boat for their first time, so we came up with a plan; my wife steered as I sat in the back with the motor and cables pushing and pulling on them until we got it down pretty good and off we went to finish out the fishing adventure; had a great day anyway) and I had the throttle box completely apart. And so at the same time you just solved the two dangling wire mystery from below my throttle box.
I look forward to opening the throttle box back open and hooking it up right and actually seeing the tach operable. I’ll keep you posted and if I run into any other problems or question I’ll reach out again; great website…
Thank you again Kevin and sorry for that long story, but I couldn’t help it we are first time boaters and having a ball.