1991 Yamaha 200 TXRP Speed Drop Activates

[pstephens46]

Doubt if anyone here has a service manual for that motor....maybe ONE does...

[99yam40]

I would think there would be specs for the sensor.
resistance at certain temps is my guess

[Doc Z....]

I would think there would be specs for the sensor.
resistance at certain temps is my guess

I have th luxury of being able to swap one from my good motors to test too.

[99yam40]

Are there any other ways to test it ??

you asked and I answered

[dray0151]

https://www.vansoutboardparts.com/se...a-shop-manuals

You might try here for a manual, not sure if this is your model or not but list a 1991 200P?

[Doc Z....]

you asked and I answered

You said resistance at temp was your guess.......I was not sure if that was definitive.

[Doc Z....]

https://www.vansoutboardparts.com/se...a-shop-manuals

You might try here for a manual, not sure if this is your model or not but list a 1991 200P?

Awesome....it is there....all 248 pages and it tells exactly how to check the thermo sensor and switch.

This whole manual is great to have........thanx.

[Doc Z....]

Update:

Tested the boat in the Hudson River and it ran perfect....no speed drop activation. This past weekend we went out to the Ocean and withing 4 miles of easy cruising.....2800 rpm the motor acted up.....speed drop activated and now the temp light flashed. The problem got worse as the weekend went on.

Came back and put it back in the Hudson River and it acted up immediately so here is what we did:

- Changed CDI box and it still acted up.
- Pulled both thermostats out and made sure water was coming out...it was.
- One side of the head was hotter though so we left that thermostat out and it ran fine.
- Went to drive back to the launch and the speed drop activated.
- Now.....pulled the thermocouple wires and it ran for an hour no problems.
- Plugged then in one at a time and found the bad one that activated the speed drop....it was on the same head the thermostat was bad
- The thermostat was brand new......***.
- I know the head was not overheating as after pulling the thermostat and running it the same hot area was now cool to the touch.

- I ordered new thermocouples to verify this fixes the problem.
- I will also install an actual temp guage.
- I will compression test the motor to make sure a head gasket is not blown.

Here is an update and it definitely would not be what would be expected:

- I put new thermocouples in the motor.
- It also compression tested fine.
- Went to the ocean and it ran flawlessly for 40 miles in calm water.
- When we hit rough water it suddenly went into speed drop mode.
- Unhooked the thermocouples - no change.
- Noticed the trim sensor going crazy so unhooked that - no change.
- Problem got progressively worse as we were testing.
- Then I noticed the Tach went out completely and did not come back on.
- So, I fiddled under the dash and found the connector to the key was loose.
- I pushed the connector back together and problem solved....ran 250 miles no issues.

My take is the connection was close enough to present an episodic problem that each time I made a change it appeared as if I fixed the problem. It turned out that it was the rough water that initiated the problem each time.

The key is in the circuit for the alarm that controls the speed drop function for both overheating and low oil and when it gets a bad ground or bad connection it will activate the speed drop..............I didn't get an alarm because the connection was bad.

[Doc Z....]

Well.....after the above finding the motor ran flawlessly for 250 miles then just like that started again:

Update 7-28-17:

We ran the boat in fairly calm water for 250 miles w/o issues but the next week after 16 miles the three light began flashing and the motor went into speed drop mode. When I turned the key off and back on it reset it but as soon as I put it in gear this time the 3 light flashed and the motor was limited.

We ran on one motor the rest of the way to Block. About 6 hours later I restarted the motor and it ran just fine all the way back home.

Summary of what has been done:
- CDI box changed.
- New thermocouple - same problem with them unhooked.
- New thermostats.
- New water pump.
- New fuel filters and spark plugs.
- Flushed the motor with Rydlyme.
- Checked connection under the dash at the key - initially this was an issue but not the last time.
- Compression test fine.
- Oil levels all fine when this starts.

The only difference in the boat is that I installed radar on its own battery with an isolator that allows that battery to charge but not get drawn upon by the starting battery. I put a yellow top optima in as a starting battery that load tests fine.

Could this be the alternator intermittently failing ??
When I bring the boat home the battery associated with that motor seems like it needs more of a charge than the one for the starboard motor. All my electronic run off the one on the starboard side but the Port side which is the problem motor has the 3rd battery on an isolator for the radar.

[rodbolt17]

3 bars flashing and an audible indicates either the CDI senses low battery voltage OR the engine oil tank is low yet the remote tank level I ok.
either one activates RPM reduction.
most older tachs have the overtemp visual on the speedometer.
both audibles should self test(sound) at key on.
a clogged remote tank filter can mimick you symptoms.

[Doc Z....]

3 bars flashing and an audible indicates either the CDI senses low battery voltage OR the engine oil tank is low yet the remote tank level I ok.
either one activates RPM reduction.
most older tachs have the overtemp visual on the speedometer.
both audibles should self test(sound) at key on.
a clogged remote tank filter can mimick you symptoms.

At key on both alarms test OK...but when I unhook the lanyard and crank the engine as recommended the good motor alarm tests OK but the other motor alarm does not go off when the key is put in the run position.

I am going to find out where the remote oil tank filter is and check that. It would just seem that that would not give me such an intermittent problem but would rather cause a constant problem.

Even though the battery tests fine I am going to replace it.

[rodbolt17]

port ket to on=port alarm sounds.
stbd key on =stbd alarm sounds.
pull the stop lanyard and turn the key to start and it should crank and sound the alarm.

[Doc Z....]

port ket to on=port alarm sounds.
stbd key on =stbd alarm sounds.
pull the stop lanyard and turn the key to start and it should crank and sound the alarm.

port ket to on=port alarm sounds.
stbd key on =stbd alarm sounds.

The above works fine but only the stbd sounds the alarm after cranking with the lanyard pulled..........the port key does NOT (this is the problem motor).

[rodbolt17]

have you tested the switch wires going to the port stop circuits?
make sure they are all plugged in, you can also test for spark while cranking with the lanyard removed, should not have any.
could be a wire not connected.

[Doc Z....]

have you tested the switch wires going to the port stop circuits?
make sure they are all plugged in, you can also test for spark while cranking with the lanyard removed, should not have any.
could be a wire not connected.

No spark with the lanyard disconnected.

I am going to look for a wiring diagram to figure out which wires are responsible for the port circuits.......it's a mess under the dash.