1998 115hp limp mode?

[Apparition]

I have a 1998 115hp with oil inject. It will not operate above 2000rpm in forward but appears normal in reverse. There is no warning buzzer sounding. Oil level in engine tank is full. Disconnecting both pink wires at temperature sensors does not change anything. Could this be low oil sensor? Is there something else that I should try? Thank you for the help!!!

[Jason2tpa]

What do you mean "not operate"? As your throttling up in forward gear the engine cuts off at 2k? Boggs down sounding like its flooding? I have the same year and hp (S115TLRW) and had a similar issue. Check out my recent thread:

http://www.yamahaoutboardparts.com/f...h26554-p5.html

About halfway through the 4 page thread you'll see where I found out why my engine was bogging down at 3k. You might be experiencing the same issue. If so it's an easy fix: the ignition choke solenoid is stuck in the activated position. When you're starting the engine and push the key in it activates the choke solenoid, which closes the carb flaps allowing a rich mix to help starting. If the solenoid is stuck in the activated position your carb choke flaps are remaining closed. As you throttle up to accelerate your not getting air into the carbs, thus not allowing you to accelerate.

[ausnoelm]

Doesn't make a lot of sense that it's OK in reverse, are you sure of that?

[Apparition]

Does not make sense to me either. At around 2000 it bogs down and will not go above 2100 or 2200. I unplugged the temp sensors and it powered off the trailer just fine. I shifted to forward and it bogged down again at 1900 to 2000. I shifted to reverse and hit 4100 pushing a wall of water. I removed the silencer/cover and nothing changed so it should not be the choke. I would like to take the boat to Florida in three weeks and there is no way I will get a repair shop to look at it in time.

Is there a sensor that tells the CPU if it is in forward or reverse?

[Jason2tpa]

And what position is the ignition choke solenoid? Engaged or disengaged?

[Apparition]

The choke solenoid attaches to the silencer and I let it hang after I took the silencer off so I think the choke would have to be open. Also when the choke was connected, I could hear it click so it must have been working.

[ausnoelm]

I kind of think when in reverse it is not operating long enough to bog down, the motor doesn't know whether it's in reverse or forward.

[Jason2tpa]

Assuming your boat is in between 16-21ft, as you're approaching 2k rpms you are not just bumped into forward gear, but nearly on plane. Which is when I believe the high speed jets kick in. The elder statesmen on this forum boscoe, rodbolt, or townsend can confirm that. And assuming temp and oil sensors are properly functioning since you're not getting an alarm, then the signs/symptoms you've described sound related to fuel. Double check the articulating arm of the ignition choke solenoid. First make sure it's connected to the carb choke, then make sure the O-ring is in place, which secures the ignition choke solenoid to the carb choke.

Another suggestion is to take the boat to wherever you launch, back the boat into the water submersing the lower half of the lower unit. Keep your trailer straps on the boat, including the bow winch hook. Remove the cowling and silencer. Start engine and put it in forward gear, slowly bringing rpms up to 2k. Pay close to attention to carb and jets. And oh yah, make sure your parking brake is on lol.

The choke solenoid attaches to the silencer and I let it hang after I took the silencer off so I think the choke would have to be open. Also when the choke was connected, I could hear it click so it must have been working.

[TownsendsFJR1300]

I'm puzzled by what's happening actually.

Couple things, has the boat been sitting awhile with untreated ethanol? IE varnishing/ clogging the jets?

Can you pull the float bowl drain screws and catch what comes out in say a super clean tuna fish can (and inspect). A pump or two of the primer to flush wouldn't hurt. Look for any debris, loose crap, etc...

And to add to the post above, not a bad idea to keep the boat secured to the trailer, back just far enough to keep the engine "wet", and stick it in forward (we want LOAD on the engine).

Trim up as needed and see if you can get any more RPM's out of forward.

The main jets (in the carbs) are working (or should be) but that doesn't explain why you ARE getting higher RPM's with load in reverse..

Not mentioned yet is the water pump. How old is it? Can you, with the engine in the water, run the engine in neutral, (and in gear) at the magic 2000 RPM and higher?

If its not going into a limp mode of some sort (false low oil alert), I'd be leaning towards clogged jets, mains specifically.

One of the other members would know how to bypass or check the oil / overheat limp mode, once they chime in...

[99yam40]

reverse does not take as much load as forward, so less fuel is needed. kind of like reeving in neutral
That is my thoughts anyway

[Apparition]

Thank you for the help!! Into will clean and inspect the carbs tomorrow night.

[TownsendsFJR1300]

reverse does not take as much load as forward, so less fuel is needed. kind of like reeving in neutral
That is my thoughts anyway

Thinking about it, I agree ^^.

If Rodbolt or Boscoe could advise re the limp mode would be very helpful.

[rodbolt17]

first test spark and compression
then verify the alarm works.
turn the key on and ground one of the pink overheat leads from the engine side of the bullet to ground.
if the horn does not work repair that before anything.

the RPM reduction is rather violent,makes the motor shake a lot.

DO NOT ASSUME anything.
trouble shoot in a practicle logical pattern.

[Jason2tpa]

Reading this causes me to think I should be routinely testing my alarms. Best to do this when the motor is running good verses testing when experiencing a problem.

So rodbolt, if you have the time perhaps you could provide us with the procedure for testing overheat and oil alarms...alarms that sound the horn.

first test spark and compression
then verify the alarm works.
turn the key on and ground one of the pink overheat leads from the engine side of the bullet to ground.
if the horn does not work repair that before anything.

the RPM reduction is rather violent,makes the motor shake a lot.

DO NOT ASSUME anything.
trouble shoot in a practicle logical pattern.

[boscoe99]

There are only three events that will set an warning alarm on 99% of all Yams and put a motor into RPM reduction mode.

(1) over temperature on two strokes and four strokes
(2) low oil pressure on four strokes and
(3) low oil quantity on two strokes that use oil an oil injection system.

The alarm (a warning buzzer/horn) will sound in the event of either of the above conditions. To hear the horn in a number of Yams simply pull the kill switch and crank the motor.

To test the over temperature system on 99% of all Yams simply disconnect the pink wire and the black wire connected to the thermoswitch. Then connect the black wire to the pink wire on the engine side harness and start the motor. Wait up to a minute or so. You should hear the horn. If you have certain Yamaha tachometers (or maybe lights on the motor or on the dash) the lights will illuminate or an icon will flash. So, with the horn you know there is a problem. With the light or icon you will know what the problem is related to.

To test the low oil quantity system in an oil injected two stroke simply drain the oil from the main engine mounted tank. Start the motor. The horn will be sounding indicating there is a problem. If you have certain Yamaha tachometers (or maybe lights on the motor or on the dash) the lights will illuminate or an icon will flash. So, with the horn you know there is a problem. With the light or icon you will know what the problem is related to. Refill the oil tank.

Four strokes use two types of low oil pressure sensing systems. One is a switch that opens to note low oil pressure. The other is a sensor that changes values with oil pressure and it lets the ECU know when the pressure is too low. To test the system in a Yam that uses a switch simply disconnect the wire to the switch and then connect the wire to the engine block. Wait a while. Maybe run the motor to 1500 RPM or so. The horn should eventually sound.

To test a sensor takes a resistor of a certain value. This test should be done by a trained Yamaha mechanic for 99% of Yamaha owners.