1985 90HP Yamaha and a 2000 90hp yamaha

[Dog12345]

I had a 1985 90 Yamaha, purchased it new....... My son wanted to start fishing so we just got through restoring boat completely. Then we found out the motor had a burnt bottom piston. So my local repair shop had a 2000 model he offered to me instead on a new one. So I purchased it.

One problem I had was the trim gauge harness on the 2000 model is different than the 1985. So I cut the plug off the 2000 and wired in the wires from the gauge. Now I am having trouble getting the gauge to measure the motor movement accurately. Basically the gauge only swing through about half the range on the gauge.

I am also wounding what to connect the gray wire to?

The original gauge worked on the 1985 motor. Why is it not working properly on the 2000 model?

[Dog12345]

Any information would be GREAT if you guys have anything. I am thinking the old 1985 gauge is not compatible with a 2000 model? does that have any merit?

[99yam40]

Boscoe need to respond on this

[walleye1]

Gray is over heat

[Dog12345]

Does the Gray connect to anything? If so what or where?

[Rossy299]

Im pretty sure you can buy a converter cable or you will need the digital multifunction tachometer gauge with trim on it. Im not sure what exact date they changed to digital but it was sometime around then. And then they changed again in like 2006 (i think)

[Dog12345]

Thanks Rossy299,

That sound correct. I have been messing around with it till I want to shoot it. I will look into a new gauge.

[Rossy299]

I have a feeling you may need the dual fuse lead from the hand control to the gauge aswell. As your one will be the single fuse with no power output?

[Dog12345]

Been doing a bunch of reading tonight. It looks like my gauge and wiring are to old to go in this motor. Now I am looking at close to two hundred dollars for wiring and a multi gauge. The problem is this motor is not oil injected so a multi gauge is a waist. I just need a trim gauge alone. Don't seem to have them available.

[Rossy299]

Yeah ive been through a similar problem and it took alot of time to sort out what parts I needed. I think theres a good chance the trim sender on the motor doesnt work anyway as there known for it. I know 02 70hp doesn't work.
Does the old tachometer work? Maybe you can get a aftermarket single trim gauge

[99yam40]

I really do not understand what the need for a trim gauge is.
you trim the motor for the load, water conditions, and speed that day