1999 yamaha 90tlrx RPMs

[99scout]

I just bought this boat and so far i have replaced all fuel parts from gas tank to carbs.new water fuel seperator and motor fuel filter..cleaned carbs and tuned..useing 87 octane 10% ethanol but gas has been treated with sta-bil ethanol treatment and ringfree from yamaha.....motorwill run fine all day until the long trip back...i will be running any where from 2500 to 5500 RPMs and then after 20 mins or so the RPMs will gradually drop and steady out at 2000...the water pump is new and working great along with the thermostat....the problem is not from over heating either.....it has great compression on all cylinders...when it does it, it will run the rest of the way right at 2000 RPMs and never miss a beat and does not sound the alarm.....this always happens in 2 foot or bigger waves when the motor is under a load....i am almost thinking that a coil is getting hot and shutting down but i think that it would stall at an idle...idles fine and will rev if i give it gas by hand at the carbs.....local shop said that the high side of the stator could be bad but why would it run all day just fine and then start acting up on the way home....prior to the motor acting up it runs strong and tip top... any thoughts

 

[jeffersondodson561]

Re: 1999 yamaha 90tlrx RPMs

Does your alarm work, if you ground the pink wire to the block with the key on do you hear an alarm? Pink wire is on the head.

 

[BaileysBoat]

Re: 1999 yamaha 90tlrx RPMs

Does your alarm work, if you ground the pink wire to the block with the key on do you hear an alarm? Pink wire is on the head.

Agreed, running in limp in mode.

 

[99scout]

Re: 1999 yamaha 90tlrx RPMs

so if the buzzer works and i replace the thermostat and it still does not fix it.....then what would you think it is? im sending my wife to get a thermostat and gasket and i will check the buzzer this afternoon(im at work right now)

 

[99scout]

Re: 1999 yamaha 90tlrx RPMs

and if it were running in limp mode would i be able to pop the throttle at the carbs and it rev all the way up...because i can and it will sit there and idle just fine

 

[axolotl]

Re: 1999 yamaha 90tlrx RPMs

Hmm, not a straight forward one.
My mind goes to limp mode, even though you mention no alarm sounding.
So either you have a burnt buzzer, or the ECU just goes into limp mode without any real reason.
Check again temps and oil level and cross your fingers its something cheap.
By the way, you can reset the limp mode by switcing off the motor...

 

[99scout]

Re: 1999 yamaha 90tlrx RPMs

Im at work right now but i walked my wife through checking the buzzer and with the key on and the pink wire grounded to the head bolts there is no sound coming from the buzzer....now what do i do.....where can i get a new buzzer....another question....how would one go about cleaning the water jackets without disassembaling the motor....somebody said to use muratic acid and fluss the motor a couple times letting it sit for 45 minutes in between flushes.....and then on the final time flush with clean hose water for a good amout of time to ensure that all traces of the muratic accid are gone....any thoughts

 

[robert graham]

Re: 1999 yamaha 90tlrx RPMs

If your motor has the automatic oiling system, then that can also trip the alarm/safe mode.

 

[99scout]

Re: 1999 yamaha 90tlrx RPMs

my m otor supposedly does not have an auto oiling system....i mix the oil right with the gas in the gas tank....i think the model is a c90tlrx

 

[robert graham]

Re: 1999 yamaha 90tlrx RPMs

Same exact year and model as my motor. The alarm circuit is very easy to check, just remove and ground that pink wire with key switch on and alarm buzzer should sound. If it's not overheating and going into safe mode, then I don't know what it is, but I'd be very interested to find out what it turns out to be. Good Luck!

 

[99scout]

Re: 1999 yamaha 90tlrx RPMs

what is the difference between the 90tlrx and th c90tlrx...does the c just mean "commercial"....somebody said that to me and they said that is the reason why my motor does not have a oil injection system...that is why i have to mix my oil and gas in the tank....anyone with more input...what is the proper name for the buzzer or alarm so i can order one...is it the thermo temp switch??????....i still am wondering if it is from the thermostat because when it does this i can still put my bare hand right on the cylinder head cover(cover with the spark plugs) and it barely has even warmth to it...not hot just barely warm and the pisser water is just barely warm...

 

[robert graham]

Re: 1999 yamaha 90tlrx RPMs

The C model has no oil injection and was sold as a "basic" model without much extra equipment, which is fine with me, since I prefer the simplicity and trouble-free nature of premix, just one less system to go wrong. The thermo/temp switch is on the right top front of your cylinder head(looking from the back of your motor), a black rubber thing held in with a small metal clip and a bolt. The overheat buzzer is located inside your remote control unit and should be tested to be sure it works, but from all indications it doesn't sound like an overheat problem to me. Maybe electrical?
Like I mentioned your motor is exactly like mine and I'm real interested to know what this problem is. We've got some great experts on here that hopefully can solve this. Good Luck!

 

[jeffersondodson561]

Re: 1999 yamaha 90tlrx RPMs

If your having trouble in choppy seas I would inspect the float in the oil tank, look for all pink wires on the engine and inspect carefully, if one of these wires is grounding against the block this could be a problem. You should have the alarm working though if it is not.

 

[99scout]

Re: 1999 yamaha 90tlrx RPMs

i do NOT have a oil injection system so that cannot be it and i did test the buzzer/alarm and it is NOT working.....now i dont know what to do.....i will probably replace the buzzer and thermostat and try it again

 

[robert graham]

Re: 1999 yamaha 90tlrx RPMs

So maybe 2 problems, a bad buzzer and an overheat? You grounded the pink wire on a bare metal area with the ignition switch on? Wonder if that thermo-switch could be bad?

 

[jeffersondodson561]

Re: 1999 yamaha 90tlrx RPMs

So you have to premix your oil? It may have had oil injection and someone removed it, I looked at your model and it shows in the service manual, having oil injection. They made models without but make sure it was not removed. You may have some high speed winding issue, or on this particular model a pulser coil is used to trigger 2 cylinders and the crankshaft position sensor controls the third. Need DVA, but and ohm test may show a short to ground.

 

[99scout]

Re: 1999 yamaha 90tlrx RPMs

Buzzer does work!!...some good news......but that means that it is not overheating right?..........so now what should i check? and yes i pre mix my gas and 2 stroke oil directly into the gas tank

 

[jeffersondodson561]

Re: 1999 yamaha 90tlrx RPMs

You potentially could have a bad buzzer but I would check it first, if you take it out of the head and bring some water to a boil and attach meter leads to each end of the sender. If you see continuity across the meter the switch is working, it is a bi metal switch so it expands to complete the circuit at a certain temperature, I believe 160. But you could be overheating still. I would pull the thermostat and check the pressure relief valve. Maybe sand could be blocking?

 

[robert graham]

Re: 1999 yamaha 90tlrx RPMs

Maybe the ECU is putting motor in RPM reduction mode by mistake? I'm very interested to find out about this, but I have no idea how to test for that type ECU error. Good Luck!

 

[99yam40]

Re: 1999 yamaha 90tlrx RPMs

my m otor supposedly does not have an auto oiling system....i mix the oil right with the gas in the gas tank....i think the model is a c90tlrx

Have you made sure this is a c90tlr?
It makes a difference and it is a good idea to let everyone know for sure if it is, as they can quit mentioning oil levels.
You can monitor the timing with a timing light while problem is happening to see if it is going into a safe mode, as that restricts the advancing of the timing. Easy to tell if that is the problem.

Sounds more like a fuel problem to me, but the timing light attached to the different plugs will also show it you are dropping spark on one or more plugs when the problem is occurring.

Fuel supply is easy to test with a fuel pressure/vacuum gauge and a clear piece of tubing placed temporarily into line between pump and carbs will show if you are sucking air into the system. look in the frequently asked questions part of the forum for a good post on testing fuel system.

Could be water or trash in carb bowls plugging jets when hitting ruff water and vibration moves stuff around, this can be happening in the tank also.

If you have a service manual and the proper test equipment you can monitor the inputs and outputs of the CDI to make sure there is not a problem with electronic parts if you see it dropping spark on any cylinders.
I do not think this motor has an ECU just the CDI unit on it, and not sure if it has a low and high speed charge coils. But the manual will tell all that needs to be tested.