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

[CHEWBAKA1973]

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.

Bad choice of words on my part.
So im told on the 704 remote the buzzer/alarm is in the key assembly. As i have tried the kill stitch test and grounding the pink wire to the engine block and briefly cranking the engine. I heard no buzzer/alarm. Is there a way to apply some voltage to the key/buzzer assembly to force this buzzer to work. Perhaps the installer hooked something up wrong? I would like to make 100% sure the buzzer is bad before spending $140 on a new key assembly because of a bad buzzer.
Thanks all for your help.

[CHEWBAKA1973]

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

i need to read what i type when im tired from troubleshooting before posting it. The switches CLOSED when they reach the proper temperature. And i did fix my earlier post.


You re correct again, pink wire on my engine. And the symptoms I originally described are exactly that, the engine retards and shakes like crazy down to about 2k RPM, after running at idle for a few mins it runs perfect again until that same retardation happens.

since I am only able to get this retardation to happen above 4000 RPMs and under load, i have no clue how I would be checking spark while underway.
I am thinking im going to fill up the tank and dropping the boat into the water this weekend and giving it another run, maybe it was a fluke.......

[ausnoelm]

seems to me you should stop chasing ghosts... fix the alarm, see if it is indeed over heating over 4,000 RPM, (which it probably is) fix that problem, go boating and enjoy your motor.

[CHEWBAKA1973]

seems to me you should stop chasing ghosts... fix the alarm, see if it is indeed over heating over 4,000 RPM, (which it probably is) fix that problem, go boating and enjoy your motor.

i plan on doing that this weekend. Some research looks promising that the PRV pressure relief valve may not be functioning properly.
so Ill be fixing hopefully the buzzer and looking there for my over heat problem.

[99yam40]

Bad choice of words on my part.
So im told on the 704 remote the buzzer/alarm is in the key assembly. As i have tried the kill stitch test and grounding the pink wire to the engine block and briefly cranking the engine. I heard no buzzer/alarm. Is there a way to apply some voltage to the key/buzzer assembly to force this buzzer to work. Perhaps the installer hooked something up wrong? I would like to make 100% sure the buzzer is bad before spending $140 on a new key assembly because of a bad buzzer.
Thanks all for your help.

the buzzer should have 12 V + to it when key is on, when grounding the pink the alarm should sound

[rodbolt17]

I think the buzzer,if bad, is about 36 dollars.
your describing a scale buildup in the water jackets.
this can and will cause false overheats.
RPM reduction will work even without the buzzer.
yellow wire from the ign switch supplies 12V to the buzzer.
the ground path is via the switch.

if it hasn't been done yes changing/cleaning the pressure control valve is a good idea.
its not your problem.

if you actually got the block and heads above 180*F it usually takes 10-20 minutes to cool off enough to open the thermoswitch.

scaling problems don't do that, the switch will open rapidly, typically 2-3 min or less.

[CHEWBAKA1973]

I think the buzzer,if bad, is about 36 dollars.
your describing a scale buildup in the water jackets.
this can and will cause false overheats.
RPM reduction will work even without the buzzer.
yellow wire from the ign switch supplies 12V to the buzzer.
the ground path is via the switch.

if it hasn't been done yes changing/cleaning the pressure control valve is a good idea.
its not your problem.

if you actually got the block and heads above 180*F it usually takes 10-20 minutes to cool off enough to open the thermoswitch.

scaling problems don't do that, the switch will open rapidly, typically 2-3 min or less.

Im told the buzzer in the 704 remote is in the ignition key assembly. I will work on that this weekend.
I did take the pcv apart and cleaned the housing best i could. I plan on replacing the grommet, plastic plunger and sping. Those are cheap enough.

What is a good way to clean the scaling in the water jackets ( those are where the thermostats are correct?)
Would something like salt away do the trick or is it a wire brush and elbow grease thing?

[rodbolt17]

the buzzer is mounted on the key switch bracket. wont be the first time I ever disconnected it and wire tied another buzzer in place.

IF its scale the only good method I ever saw was removing the head covers AND heads and manually scrape it.

[CHEWBAKA1973]

yellow wire from the ign switch supplies 12V to the buzzer.
the ground path is via the switch.
i

The switch you are referring to is the thermo switch at the motor correct? Any idea what color the ground wire to the buzzer would be coming from the switch?

[99yam40]

http://www.yamahaoutboardparts.com/f...g-th19434.html

Good read on this thread on his 115

[CHEWBAKA1973]

http://www.yamahaoutboardparts.com/f...g-th19434.html

Good read on this thread on his 115

Thx for posting the link. I will pull the t stay covers off and re take some pictures. Mine wasn't nearly as bad as this guy's and im not sure if it is calcium deposits or salt or something else.

[boscoe99]

Here are some diagrams with respect to your motor and a 704 key switch that might help with situational awareness.

Note that some motors will go into a false RPM reduction mode if electrical power is irratic to the CDI. Check your battery cable connections at both ends for cleanliness and tightness. Also, check any other cables that may be connected from the battery cable posts on the motor to anywhere else on the motor. Look at the 20 amp fuse and make sure it and the terminals that it attaches to are clean and tight.

Maybe disconnect and reconnect the connectors running to the CDI to try and scrub off any corrosion that there may be on the terminals within the connectors. Not saying this is your problem but these checks are simple, don't take much time and are free. They might not help but they won't hurt.

[TownsendsFJR1300]

Do you flush the engine with fresh water when done (I'm assuming your using it in salt water (Tampa Bay)? Preferably on the muffs?

My neigbors 200, 2 stroke had what turned out to be an overheat issue.

Engine hit approx 3,800 RPM, then shut down RPM's. His buzzer worked but you could barely hear it (he couldn't). Always pissed well, installed new water pump, one thermostat was sticking. Got the RPM's higher (about 4,000) but the engine still did the same, just at a higher RPM.

Eventually pulled the heads, the corrosion, next to the cylinders and on the head and in the water jacket was really bad..(He was one NOT to flush often). The salt build up was about 4" deep, especially on the lower water jackets. I honestly don't know how that engine ran as 90% of the water to the lower cylinders was closed off due to salt (SW Florida)...

After much scraping, picking, etc, it was re-assembled and ran like new. Full throttle , no problem!!!

[CHEWBAKA1973]

I think the buzzer,if bad, is about 36 dollars.
your describing a scale buildup in the water jackets.
this can and will cause false overheats.
RPM reduction will work even without the buzzer.
yellow wire from the ign switch supplies 12V to the buzzer.
the ground path is via the switch.

if it hasn't been done yes changing/cleaning the pressure control valve is a good idea.
its not your problem.

if you actually got the block and heads above 180*F it usually takes 10-20 minutes to cool off enough to open the thermoswitch.

scaling problems don't do that, the switch will open rapidly, typically 2-3 min or less.

Turns out previous owner which also installed the engine on my boat neglected to install the warning buzzer. I went to Yamaha parts dealer and purchased one. It was closer to $60. Anyway that problem is solved. I verified the buzzer works by shorting one if the thermo switche wires and turning the ignition on. Buzzzzzzzz.

[CHEWBAKA1973]

Here are some diagrams with respect to your motor and a 704 key switch that might help with situational awareness.

Note that some motors will go into a false RPM reduction mode if electrical power is irratic to the CDI. Check your battery cable connections at both ends for cleanliness and tightness. Also, check any other cables that may be connected from the battery cable posts on the motor to anywhere else on the motor. Look at the 20 amp fuse and make sure it and the terminals that it attaches to are clean and tight.

Maybe disconnect and reconnect the connectors running to the CDI to try and scrub off any corrosion that there may be on the terminals within the connectors. Not saying this is your problem but these checks are simple, don't take much time and are free. They might not help but they won't hurt.

Thank u for these schematics. They were very helpful. Buzzer fixed. Now on to the possible overheat or bad electrical connection problem.
I did purchase a new popet valve assembly. Yamaha redesigned the plunger part of it. It no longer fits into the grommet but it has a dome like end to deal against the grommet seal.