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WIring for tach

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Seanfish

Member
I have a tach installed on the boat. Why it was never wired in, I have no clue.

Images attached, it's an 8pin connector, and I have no idea what connector(s) I need to make it functional.

1985 Evinrude 70hp with the standard OMC control box throttle.

trying to get pics to upload...not sure if I need a certain post count first

6B37D77E-18EF-4750-A70F-A17067DE8B26.jpg
 
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That looks like the back side of a tach that has system check. On the face, are there places where it says "HOT", 'Low oil', 'CHK ENG', and 'NO OIL'? If so, I'm not sure the year of your engine is directly compatible with that 8-pin harness. You should be able to look up the pin-out on that tach, get an 8-pin harness, and then wire that in directly to your control box. There should be a tach connection on your box but my guess is it's a 3-wire setup which i think would be BLACK (ground), GREY (tach pulse), and PURPLE (12V). You might have a blue wire in that connector which would be for back lighting of the gauge face.

Something like this harness probably plugs into your control box.
https://www.marineengine.com/newparts/part_details.php?pnum=OMC0174732

Hopefully someone else has the pin diagram for your tach. If you get that info you can adapt the tach to work with your controls.

KJ
 
kevinj said:
That looks like the back side of a tach that has system check. On the face, are there places where it says "HOT", 'Low oil', 'CHK ENG', and 'NO OIL'? If so, I'm not sure the year of your engine is directly compatible with that 8-pin harness. You should be able to look up the pin-out on that tach, get an 8-pin harness, and then wire that in directly to your control box. There should be a tach connection on your box but my guess is it's a 3-wire setup which i think would be BLACK (ground), GREY (tach pulse), and PURPLE (12V). You might have a blue wire in that connector which would be for back lighting of the gauge face.

Something like this harness probably plugs into your control box.
https://www.marineengine.com/newparts/part_details.php?pnum=OMC0174732

Hopefully someone else has the pin diagram for your tach. If you get that info you can adapt the tach to work with your controls.

KJ
Click to expand...


Boat is rigged with 1985 Evinrude 70hp. I may have just figured out that I need an adapter to go from the binnacle to the tach. You are correct it is in fact a system check gauge. It appears I am simply missing the 3 wire connector from binnacle to the gauge.

No idea where to find that 3 pin connector to the 8pin connector on the gauge cable if its even made. I'm also not opposed to making one if I can find the right connectors and pin outs. Obviously I know the system checks wont work, but a tach is something I'd really really like to have on my boat. If anyone can point me in the right direction it would be greatly appreciated.
 
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I found the pinout after some searching, and it appears I only need pins 1 (+12V), 2 (Ground), & 3 (Tach signal) as I am not concerned with the actual system check functions given this is a 1985 motor.

I *THINK* this should work by simply using only pins 1/2/3 and connecting them. If not, please correct me if I'm wrong before I spend an unnecessary $50

https://www.marineengine.com/newparts/part_details.php?pnum=OMC0174732

https://www.amazon.com/Deutsch-8-pin-Pigtail-16AWG-Certified/dp/B07G5LGWN4/ref=asc_df_B07G5LGWN4/?tag=hyprod-20&linkCode=df0&hvadid=309807586683&hvpos=1o1&hvnetw=g&hvrand=4024888101505322605&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1015153&hvtargid=pla-597760993644&psc=1
 
Yes, I believe those should be the only 3 wires you need. The harness for your control box will also fit up to any generic 6-pulse tach if the one you have happens to not work.
 
I appreciate the verification. Main reason for connecting this is two fold.

1) IMO, it's the most important gauge on a boat with an outboard.
2) I want to make sure I'm propped right on my 18ft single engine cat. which is a whole different animal altogether. But I cant calculate slip numbers without a tach.
 
Seanfish said:
I appreciate the verification. Main reason for connecting this is two fold.

1) IMO, it's the most important gauge on a boat with an outboard.
2) I want to make sure I'm propped right on my 18ft single engine cat. which is a whole different animal altogether. But I cant calculate slip numbers without a tach.
Click to expand...

Understood and in agreement. If that tachometer proves to be incompatible, get one that is... the end alternative result is usually quite expensive. :(
 
Seanfish said:
I appreciate the verification. Main reason for connecting this is two fold.

1) IMO, it's the most important gauge on a boat with an outboard.
2) I want to make sure I'm propped right on my 18ft single engine cat. which is a whole different animal altogether. But I cant calculate slip numbers without a tach.
Click to expand...

Good plan on the tach. I think there are 2 gauges that are vitally important:
#1 Tach
#2 Water pressure Gauge

Over the Independence Holiday I was down at my dock and watched one of the lake patrol boats get towed in. It had an Etec 90HP that was locked up tight. The head officer took the hood off and could not even touch the flywheel without roasting his fingers because it was flaming hot. My guess is the kid driving the boat either drove it with something covering the water intake ports or the water pump was shot. Either way there was no water pressure gauge on the dash so he couldn't see if anything was going on. Also, he probably ignored any warning horns so the engine got massively overheated and is most likely junk.

Moral of the story.....water pressure is your friend.
 
Water pressure is important. Water pump gets done every other year on every boat I've owned. Cheap insurance. Along with turn around and look at hte damn thing every once in a while. Mine is an open boat with a clear view of the tell tale, so it's not difficult for me.

Had a Suzuki DT40 impeller fall apart while flushing it at home in a trash can full of water. If you cant hear the overheat alarm, something is wrong with you. Shut it down within about 10seconds. Let cool, fired back up, and realized I had no water pump. Shut down and replaced, and zero damage to motor. Those alarms are there for good reason and if you listen to them, you can often get away with a simple fix rather than a complete overhaul. I am fairly certain the E-tec you mentioned above, is now destined for the outboard graveyard.

Edit >> Do I have a water pressure signal coming out of my engine?
 
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