1994 Yamaha 115HP 2 Stroke Alarm at high rpms

[ezzrider]

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

Try the link here for your manual. It may be the 115S if it is a 94. It may have better info than one of the aftermarket ones. As stated you might want to start looking at blocked water passages but if this is a freshwater engine they re not as bad as saltwater use. To bad gauges don't work that would help some too. Not a 2 stroke user but just because an oil tank has oil it may not be getting enough through to the engine at rpm's. the manual also has a couple of pages on troubleshooting.

Thanks. I was able to download the service manual from this link.

[ezzrider]

What is the downside to just taking out the thermostats at least for testing or flushing before putting in new thermostats?

[TownsendsFJR1300]

What is the downside to just taking out the thermostats at least for testing or flushing before putting in new thermostats?

There is no down side. I'd personally do so you can see if it's not opening fully, stuck, etc... If it never opens fully, you KNOW you found the issue or at least part of it..

IE testing the t-stats in hot water, not running the engine

[99yam40]

If you mean to remove and run the motor without them in place, the stats help keep the motor temp where it should be so that it will burn the fuel properly.

plus they restrict the water flow some to help make sure all of the water is circulated evenly as it was designed.
without them in place there will be cold and hot spots

[zenoahphobic]

If you run the engine without replacing the plates temporarily, you can compare the water flowing of each of them to determine if a particular bank has a restriction by only replacing one at any time. Downside is water will be pouring out onto and down inside. Don't run like this for long as said above you may make the engine hot and cold in places, and your alarm may not sound because of the increased flow of water.

If you run with both plates back in place, similarly the alarm may not go off because of the increased flow. If no alarm will mean nothing.

To check your thermostats place them into boiling water and observe the rate and amount of opening, if very little you have found the culprit.

If things look reasonable as you say, you may have some other obstruction, such as sand, weed etc. that may have occurred recently, and/or has worn your pump.

[ezzrider]

I replaced both thermostats. I initially removed both and ran the engine. I got no alarms but was running at high idle. After replacing the thermostats with new ones I ran again at idle with no issues. Seemed to have a stronger water jet out of the pee hole. Was interesting to me as was recommended here in this thread when I put the engine down in a large trash can filled with water I got no alarm but when I tried the same thing with ear muffs as water on high from the hose I got an alarm. I tried to replace the water pump impeller also but could not get the lower unit to break free. All the bolts were out and I used a rubber mallet and hit around the sealing area but no go. I just could not get it to break free. Going to put back in water and test tomorrow and see if the new thermostats made a difference. Unfortunately with one of the thermostats I got a leak at the cover even though I installed a new gasket. I took back off and looked ok but still leaked a little. I am going to get and use some RTV High Temp in morning. My gauges actually light up but I can't see anything on them so they are getting power. They are the original Yamaha Gauges. Probably the sun has faded them over the years to the point of too much distortion. If I get an alarm again tomorrow in water an going to need to figure out how to break the lower unit free. Has been sitting in fresh water.

[99yam40]

man if the drive shaft is rusted into the crank you will have major problems.
It is a very good idea to pull the lower often and clean /grease up shafts and bolts to keep this from happening

[panasonic]

You said you had changed the water pump a year ago? If so the lower unit shouldn't be stuck to bad. Are you sure you have all the bolts out. There is probably one under the trim tab. Check your manual make sure you got them all.

[ezzrider]

You said you had changed the water pump a year ago? If so the lower unit shouldn't be stuck to bad. Are you sure you have all the bolts out. There is probably one under the trim tab. Check your manual make sure you got them all.

Yep I forgot the bolt under the trim tab and I took the trim tab off! Dang.