1998 yamaha 115 hp false rpm causing rpm reducer to kick in?

[CHEWBAKA1973]

Yep, sounds like a temp issue. 4000 rpm sounds like the trigger point where I assume the temp exceeds parameters and it tries to save the engine from damage and drops it to 2000. I would replace thermostats as they are designed to open at a certain temp, maybe 4000 rpm it reaches that temp but fails to open some or at all. Good to do and fairly cheap and easy as well. Try to get a used tach or borrow one to see if it does the same thing as your current tach.

So there are 2 thermostats for my engine, and also two thermo switches. whats the likelihood that one of the switches is causing this false limp mode?

[ausnoelm]

Can someone tell me how this is anything at all to do with "limp mode" you are still tunnel visioned about this.

[CHEWBAKA1973]

Can someone tell me how this is anything at all to do with "limp mode" you are still tunnel visioned about this.

the way the engine is acting, 4000 rpms it drops down to max 2000 rpms until i let it idle or shut off the engine. isnt that how the limp mode works?

perhaps the RPM spiking issue and the way the engine is behaving over 4000 rpms are two completely separate issues and I just assumed they were related.

What do you think is going on?

BTW, I talked to the local Yamaha parts dealer, they seem to think it may be thermostat, poppet valve related. he suggested to remove the thermostats, drop them into boiling water to see if the open/close freely.

[rodbolt17]

quick test of the alarm.
pull the stop lanyard and crank it.
if it sounds your good if it does not fix that FIRST.

get over the limp mode sheet.
find a real tech.

do you understand what a thermo switch is?

[CHEWBAKA1973]

quick test of the alarm.
pull the stop lanyard and crank it.
if it sounds your good if it does not fix that FIRST.

get over the limp mode sheet.
find a real tech.

do you understand what a thermo switch is?

Thx ill try that test.
Looks like i may have to. Any harm in replacing thermostats and trying to see if thats my problem. Yes I know what the thermo switch is. It's what triggers the engine to alarm and go into limp mode if it overheats.
Silly question. Where would this alarm/buzzer be located??

[ausnoelm]

You seem to have a couple of things going on (or not going on) and this limp mode has got you fixated, first off you have to make sure your alarm works, then see if it IS over heating, of course it won't hurt to replace the thermostats, but it also won't help if they are OK. Trouble shoot before throwing parts at it.

[CHEWBAKA1973]

You seem to have a couple of things going on (or not going on) and this limp mode has got you fixated, first off you have to make sure your alarm works, then see if it IS over heating, of course it won't hurt to replace the thermostats, but it also won't help if they are OK. Trouble shoot before throwing parts at it.

Agreed 100%. But where do i start. All i have to go on right now are the symptoms that i described above already.
I am totally open to troubleshooting suggestions. Thx

[Seacraft12]

Troubleshooting: test alarm when kill switch is pulled. If it makes a noise, good. If not, replace it. Pull tstats and do the boiling water thing, if they open there good, if not replace them

[99yam40]

make sure buzzer works
make sure temp switches work in spec
make sure stats work in spec

A pot of water and something to measure the water temp while heating it is simple.
need a meter to look at switch, but stats just need your eyes

[CHEWBAKA1973]

make sure buzzer works
make sure temp switches work in spec
make sure stats work in spec

A pot of water and something to measure the water temp while heating it is simple.
need a meter to look at switch, but stats just need your eyes

Great. What re the specs?
Tried looking up the part number for my 1998 C115TLRW and wouldn't ya know it my year is the only year that does not have a buzzer listed. ????????

[rodbolt17]

depends on the control box.
703 side mount the buzzer is in the box.
704 binnacle mount the buzzer is on the key switch assy.

thermo SWITCH.
its ON or OFF.
OPEN or CLOSED.

there is NO limp mode.

[CHEWBAKA1973]

depends on the control box.
703 side mount the buzzer is in the box.
704 binnacle mount the buzzer is on the key switch assy.

thermo SWITCH.
its ON or OFF.
OPEN or CLOSED.

there is NO limp mode.

Good info thx. What is the spec for thermo switch to open? Is it testable or just replaceable?

[rodbolt17]

switch closed 183-194 *F
switch open 140-165*F.

[CHEWBAKA1973]

switch closed 183-194 *F
switch open 140-165*F.

great thx, any specs on the thermostats?

[99yam40]

your life will be a lot easier if you get a service manual for your motor so you can look things up if you want to work on it

Procedures and specs are all in there so you do not have to spend days trying to find some with the info you need that will post on your thread