2007 Yamaha 90 2-stroke going into Limp/Safe Mode

[hppants]

(I did search before I posted - found a similar thread for an '87 90, but my problem is different, thus a new thread)

Greetings:

I am the original owner of a 2007 90TLR (90 2-stroke) outboard. The motor has approx 750 hours on it, and has been well maintained. It has good compression (120 in each hole), spark plugs are new, fuel pump is only a few months old (Yamaha F/P), and the water pump is about 1 year old (complete Yamaha pump, per my usual service practices).

Not always, but every once in a while, after the motor has been running at 4,000-ish rpm for at least 5 minutes, the motor will go into limp mode, whereby it won't take any throttle much past 2000 rpm. When that happens, I simply run it at fast idel chugging along for a couple of minutes, and then with no rhyme or reason, I start trying it. At some point shortly thereafter, I can throttle up and the motor will run normally.

I am still running the oil injection and the tank is full of oil.

The tattle tale is pissing a heavy stream as normal.

When it goes into limp mode, I do NOT hear a horn at the remote control box.

Any ideas on where to start? I'm more of a parts changer, admittedly, than a mechanic. The experts here might have to dumb it down for me. I do know enough not to get over my head.

Thanks in advance for any assistance.

 

[boscoe]

First and foremost, it is not a limp mode. It is not a safe mode. The motor is trying to save itself when the operator does not shut it down immediately upon hearing the warning horn.

Start with fixing the horn. Pull the kill switch. Crank the motor. The horn should sound. If not, find and fix that problem.

I would start by adding a Yamaha tachometer (or led lights) that will tell you why the motor is doing what it is doing. Low oil, over temperature, or the CDI is thinking that is so even if it is not.