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

[CHEWBAKA1973]

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

another great idea! this is why i love posting my engine problems on this forum. Thank you all for your help so far, all i need to do is find the time to do this trouble shooting.

Can you recommend a good service manual for my engine??

[ausnoelm]

There is only one service manual, the GENUINE one, do not buy the generic manuals, or the cheap Ebay copy CD's, spend the money and buy the proper one, it will be worth it, and hopefully after Rodbolts post, you will forget the limp mode business forever.

[CHEWBAKA1973]

There is only one service manual, the GENUINE one, do not buy the generic manuals, or the cheap Ebay copy CD's, spend the money and buy the proper one, it will be worth it, and hopefully after Rodbolts post, you will forget the limp mode business forever.

Don't get me wrong. I never doubted you. I guess the way i described the symptoms and my choice of words were wrong. When the fault occurs the engine runs at 2000 rpms and sounds like its running on half the cylinders.

[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?

I tried that alarm test. Pulled the lanyard and cranked the engine. No buzz no sound. With the lanyard removed does the ignition still allow the engine to crank? Btw I have a 704 remote con*****er. Looking at the wire harness i do not see anything resembling a buzzer. It seems I have several problems going on here.

[Speedcop]

Hi CHEWBAKA1973
If I can chip in here, I have 130 Yamaha (which is more or less the same as the 115) and I had all sorts of problems with RPM reduction, alarms going off, etc etc.
On advice from many learned folk on the forum, I cleaned carbs, fitted fuel pump kit checked oil reservoirs, etc. My problem turned out to be the electrical feed from the battery! I had fitted a “kill switch” or battery isolator, and the thing was corroded and rusted inside! I replaced this, cleaned my battery connections on both ends and PRESTO problem solved!!
Take a look at my threads on the forum. Go to the members list, find my user name “Speedcop” and read through my posts and the answers from the experts. You may pick up some brilliant advice from Rodbolt and the guys.
Good luck!
Dennis.

[CHEWBAKA1973]

Thx speed cop i did look over your info. Was able to find the service manual for my engine.

I finally had a chance to look into this issue. I pulled bother thermostats and did the suspension test in water. Both opened as the specs specify. I did see some corrosion in both thermostat housing. I ll try to attach some pictures. So since I believe the thermostats are functioning do i verify the thermo switches are in spec?

[99yam40]

it is always good to know if they are working in spec, then if the temp alarm goes off you know there is a real problem

[ausnoelm]

I tried that alarm test. Pulled the lanyard and cranked the engine. No buzz no sound. With the lanyard removed does the ignition still allow the engine to crank? Btw I have a 704 remote con*****er. Looking at the wire harness i do not see anything resembling a buzzer. It seems I have several problems going on here.

I hate to sound cranky, but the more you "FIDDLE" the more faults you are likely to find, because you are causing them, be thorough and be methodical in your trouble shooting, do not jump from place to place pulling things to bits to "test", after all, we/you really don't know for sure what the fault is yet.

[CHEWBAKA1973]

I hate to sound cranky, but the more you "FIDDLE" the more faults you are likely to find, because you are causing them, be thorough and be methodical in your trouble shooting, do not jump from place to place pulling things to bits to "test", after all, we/you really don't know for sure what the fault is yet.

I am all open to suggestions. Thermostat test was simple enough but it doesn't seem to be the issue. Faulty thermo switch could be my next test, unless someone else has any other ideas.
I did find out with the 704 con*****er the buzzer is in the ignition key switch.

[ausnoelm]

read Rodbolts test with the lanyard removed very carefully, then re-read your results.

[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

Buzzer dont seem to work.
Thermostats work within spec as do the thermo switches. Both switches CLOSED!!! at 87.2 degs C.
So this is not an overheat issue.

[CHEWBAKA1973]

read Rodbolts test with the lanyard removed very carefully, then re-read your results.

I'll try that next. Or should I say I'll try it again

[Speedcop]

Overheating query

Have you checked and cleaned your electrical connections?
Battery - both ends? Bad or rusted connections can cause the same symptoms. ie. RPM reduction and alarm.

[99yam40]

I tried that alarm test. Pulled the lanyard and cranked the engine. No buzz no sound. With the lanyard removed does the ignition still allow the engine to crank? Btw I have a 704 remote con*****er. Looking at the wire harness i do not see anything resembling a buzzer. It seems I have several problems going on here.

the kill switch pulled will allow the starter to turn the motor , but it will not fire up. It grounds the ignition keeping plugs from sparking and should set off the buzzer. You need to get the alarm working It will help your troubleshooting and it is good to have things working as they should/

Are you sure they opened at that temp or did they close?

When the over temperature switch closes it grounds the pink wire(I believe that is it color on your motor) the alarm buzzer should sound and I believe the timing is retarded to limit the RPM to about 2 K. You can disconnect the pink wire and ground to block to test with key on. If you disconnect the pink wires one at a time while the RPM reduction is present you can find which one is setting it off if that is the problem

Not sure why Rod says there is no limp( safty) mode, maybe just the wrong word.

If the switches work in spec as they should and you are getting an RPM reduction, you need to find out if the timing is changing or if there are cylinders not sparking as you have said in the past.

Could be you are loosing spark on some cylinders due to a coil or wire heating up and not functioning as it should

[rodbolt17]

its not a "limp" mode.
its a forced RPM reduction by misfireing cylinders to alert the operator that catastrophic failure may occur.

first thing is fix the audible alarm.