2003 Yamaha 90 won’t rev past 2000 RPM

[Apalacio1]

Ok, so I have a 2003 Yamaha 90 2 stroke. I have always had prom Lena with the motor and have had it looked at by several people. I have had the carbs rebuild a few times and has some minor electrical problems resolved. Lately when I take the boat out it will intermittently work and not work. Mostly not. I took it out last weekend and the second I had the chance to go fast it stops at 2000 rpm and the engine pretty much sounds like it’s vibrating to death and doesn’t wanna go any higher. But I stopped the boat and ate lunch for about 20 min, turned the boat back on and it stopped working once again. After I turned the boat off after running while it was working for a while, it again stopped going past 2000 rpm. I was told the problem was the rectifier and cdi box, but I replace them with pre-owned ones and the problem persists exactly the same.(I understand the parts I put in May be faulty but it’s unlikely that the problem stays exactly the same). I would like to know if you guys know the voltages I chills be looking for from the cdi and rectifier and whatever else I can test that may be faulty. Thanks

[99yam40]

do you have gauges and alarm system on this motor/boat?
if so are they functioning as they should?

sounds like the motor is going into RPM reduction due to overheat or low oil signal going to the CDI
That limits RPM to 2000

[Apalacio1]

Yea it does have an alarm system. Not 100% sure it’s functioning but I have had the alarm go off in the past. Since my outboard is oil injected and has an oil reservoir i have had a feeling in the past that the sensor on the tank is bad and may be sending a bad signal. Is it possible to just disconnect that as long as I know there is oil in the tank? But then again since I do have an alarm, it has not gone off when this has occurred so may not be this. (Also for the gauges I have simple mechanical tach and speedo)

[Apalacio1]

What I was told before I put the pre-owned cdi in, is that once the engine gets hot, the cdi starts acting up. But after I put this pre owned one in , it started acting up 5 minutes after starting it. So, I’m starting to question wether or not it is truly the cdi.

[99yam40]

I would test the buzzer and alarm system
troubleshooting to find the problem and fixing it is way better than bypassing safety systems

On some motor you can pull the man overboard switch and then try to start the motor to see if the buzzer sounds

disconnecting the wires to the overheat switches and shorting the wire or grounding the signal wire should set the alarm with the key in on position

draining the oil tank and then turning on the key switch might give the low oil signal

Some motors need to be running for a set time period before activating the safety, but I do not think a 2003 90 would be one of those

sounds to me more like an overheat condition happening

test the buzzer and the switches
pull the switches and test in a pot of water as you heat the water and monitor the temp and switch operation

[Apalacio1]

Update: I just drained the oil tank and turned key to on position. No alarm sounding. In the past when the alarm has gone off for whatever reason I do remember turning the key to this position and it would still be sounding until it was safe to run again. So I think either the alarm is bad or the oil sensor is bad. I also have had the alarm randomly go off in the past, In ex: the boat was sitting for about an hour and I came to start it and the alarm instantly went off.

update 2: alarm doesn’t function but I can see that the float for the oil is working because the alarm does make a slight noise when I move the float up and down.

[99yam40]

so , time to check for overheat
did you try pulling the man overboard kill switch and turn key to start to see if that could get the buzzer to sound?

[Apalacio1]

This boat from as long as I can remember does not sound the alarm with the kill switch unplugged. The thermostat seems to be ok also. Not sure exactly how to test without getting it warmed up though. All o did was test the wires and ground them together and it makes the alarm go off.

[99yam40]

Did you try to start the motor with the kill switch pulled to see if the buzzer sounds?
the motor should turn over, but not start, and I believe should sound the buzzer

so now you are saying you tested the overheat alarm and the buzzer does work??

[Apalacio1]

The issue is the buzzer technically does not work. When I tested it by touching the two thermostat wires together, the buzzer makes the faintest sound it could possibly make but you can still hear it. I do not believe o would hear it while cranking the engine and I don’t remember the buzzer ever going off whilst cranking the engine without the kill switch.

[99yam40]

fix the alarm so you know when something is calling for PRM reduction mode.

in the past while the buzzer worked, did you try to start the motor with the kill switch pulled to see if the alarm sounded?

you say it never did, but not many people try that on purpose, maybe by accident some time