New Yamaha round multi-gauge Install issues

[firefighter1968]

The back story :
I purchased a 2006 Yamaha f115 four stroke which was a tiller model that I swapped over and am making into a front/remote control unit. After purchased all wiring, controls, etc I’ve encountered issues with the tach gauge.

The tach gauge shows full trim with the top bar blinking. Despite playing with the trim sender at the engine I can’t get that gauge to change. In addition to the blinking trim it also intermittently shows the water in fuel warning light.

I checked ohm output at the trim sender and it seems to be working. Started at about 94 ohms down to 0. I checked ohms at the connection behind the tach gauge and the white/red wire has a proper ohm output also but only when I ground it to the boat( if that makes sense ).

im not a technician by any means. Any thoughts out there from anyone ?

[firefighter1968]

Secondary question to this one.....
neither buttons on the gauge do anything. No matter if I hold them for four seconds , push both at same time, etc. I tried a couple used gauges and now have a brand new one. They all behaved exactly the same. Any chance something is installed incorrectly?

[fairdeal]

We can probably help you work it out -
but Yamaha has made numerous changes over the years
to the gauges, to the wire colors,
so it can be confusing until we all get on the same page.


First - is this a round, black, Yamaha tach, with digital display -
and a bunch of individual wires coming out of a rubber plug on the back?

then, are there two 4-wire plugs? or only one?

where is this white/red wire ?
does it come out of the back of the tach?
or is it in the harness that the tach plug connects to?

your measured trim sender ohm range seems off -
but lets let that go for now

[firefighter1968]

Firstly yes this is a round black Yamaha gauge. The model is 6y5-8350t-00

Coming out of the back is a large group of wires as follows

Pink, grey, orange, and black with white , go to a female four
pin

White with red, blue with white, green with red, green with white go to Male four pin connector

The remaining wires are singles : yellow, red, black, green, And blue


the trim harness running to the motor has these colours:

female four pin connector: green with red, solid green, blue with white, and white with red

male four pin connector : orange, grey , black , pink

[fairdeal]

very good.

Ok - Yamaha makes the same tach suitable for use on many/most models they have ever made -
as a result, there are "more wires than you need" -
of the 8 wires in the 2 4-pin plugs,
only 3 are used, to perform 3 functions
(and yourengine only has one 4-position plug to connect to the tach)

At the tach end, the wires used to communicate with the engine are:

pink - trim position
green w/white - overheat indicator
green w/red - low oil pressure indicator

One or more of those mate with a different color
when they connect with the harness plug -

and then, at the engine, the colors of the harness wires
mate with different colors of the engine plug -

whose wire colors are:

pink - trim position
pink w/ black - overheat indicator
pink w/ white - low oil pressure indicator


Also -there are settings dipswitches inside the back of the tach,
which - if it is a 'used' gauge - may need to be changed:

[firefighter1968]

Thx for the great description. As of right now I have the motor wired up correct based on what your saying. I have the dip switches correct (up, down, up). I’m leaning towards a bad trim sending unit maybe.

what I still don’t understand is why my gauge doesnt allow me to select and scroll through the settings etc. They are very basic units with only two buttons but I still can’t do anything with those buttons.

[fairdeal]

gauge doesn't allow me to select and scroll through the settings etc. They are very basic units with only two buttons but I still cant do anything with those buttons.

they don't do much:

- select whether you see 'total hours' , 'trip hours', or no hours display
- reset the 'trip hours' to zero

"total hours" on that model gauge is
"total hours that the gauge was connected to a running engine"
NOT the actual hours stored in the engine ECM

so until a new gauge has been installed,
and the engine run for more than 60 minutes,
both total and trip is zero

[fairdeal]

re the trim sender:

with the engine fully up (arm of the sender fully up)
the sender resistance is high - should be >250

so with the sender disconnected (can't get higher resistance than that!)
the gauge should be flashing 'full up'

when the engine is fully down - arm of the sender fully wound against its spring -
the resistance is low - approaching zero ohms

if you short the pink wire to ground,
the gauge should read full down


Also - on a 2006 or newer motor -
there is a pink wire 'jumper' on the engine harness,
in the front of the engine pan.
Originally wrapped in yellow tape.
For your gauge, those pink jumper wires should not be connected.
If for some reason a previous owner changed it -
that will mess up your trim gauge reading.

[firefighter1968]

Update.

I just figured out that the trim wiring harness provided to me was wrong. Not plug and play as I was told. I “jumped” the wire they was carrying the signal from the trim sender over to the pink wire behind the gauge and bingo I got a reading. I never would have figured that out without you telling me that. I’ll use your latest info to navigate through the rest. I hope this is the end of this saga.

thank you very much fairdeal. !!!!