Yamaha 2003 90hp 2 stroke overheat?

I have had a couple of issues with my 2003 motor recently. I thought the battery was dead since it would not turn the starter when the switch was engage but a new battery and cleaning the connections made no difference.

I finally got it to turn over and it started right up. I decided after playing with the switch that it appeared to be an intermittent problem and most likely an issue in the ignition switch. I replaced the switch yesterday and thought my problems were behind me.

I took it to the lake this afternoon and after running the engine for about 10 minutes I was cursing down the lake at about 3000 rpm when the temp light and horn came on. I brought it back to idle and checked to see that water was flowing out of the cooling overflow, it was.

I cut the engine off and pondered the situation, then decided to check the switch to see if anything was shorting out or loose since the temp warning light and buzzer are in the wiring bundle that I pulled on yesterday while changing the switch. I found no problem and the light/buzzer continued to come on as soon as I turned the switch on....even without starting the motor.

After about 20 minutes I decided to limp it back to the dock. I made it back fine with no indication of the motor heating...other than the warning system. I trailered the boat home about 10 minutes from the lake and when I tried the motor at the house the alarm was silent. I started it with water hooked to the intake and ran it for 30 minutes at various rpm's with no over temp alarms. I started and stopped it several times and never got the alarm again.

This motor probably has less than 100 hours on it, I bought it new and it has always been stored on a trailer and only run in fresh water. I checked the intakes and found no indication of blockage. Water comes out the outflow normally and the water felt cool the whole time it was running.

Any suggestions on what to check or how to be sure if it is an indicator fault or actually a heat issue?

Thanks,
Forest

Re: Yamaha 90 2 stroke overheat?

if it was a heat issue, the water coming from the tell tail would have been very hot, and the motor should have gone into slow, or protect mode . I would recheck the wire and make sure I did it right and nothing is shorting to ecah other. next time pull the cowling off and see if the heads are hot. if so cooling problem, if not, wiring problem.

Re: Yamaha 90 2 stroke overheat?

You need to understand how your cooling system works, firstly the water out the tell tail can be cool and the motor overheat, the tell tail indicates that water is pumping, however if the thermostat and or thermostat bypass valve doesnt open the water will not circulate through the power head and it will over heat despite water flow out of the tale tail.

Re: Yamaha 90 2 stroke overheat?

Thanks for the reply. I was thinking the tell tail was not a good temp indicator based on research I have done on the web. I ran the engine again on the trailer with the water hose connected and still no sign of overheat. I am really wondering if there is a way to check to see if there is really a heat problem?

The head gets hot but not untouchable. I can lay my hand on it for about 30 seconds before it gets uncomfortable to the touch. I wish there was a temp guage on the motor but not sure if there is a an easy way to add the heat probe and install one....any suggestions.

How about a hand held infrared heat sensor. Any idea what temp the heads should read when warmed up?

On the other hand the thermostat and bypass valve looks simple to change, maybe that should be my next move?

Re: Yamaha 90 2 stroke overheat?

Normal operating temp is between 140-165 degrees. Alarm will come on between 183-195 degrees.

Re: Yamaha 90 2 stroke overheat?

Thanks for the replies. I put the boat back in the lake on Thursday and in about 10 minutes the heat alarm was going again. I pulled it out of the lake and took the water pump out on Friday afternoon. A couple of the vains were in pieces and some rubber scraps were mostly blocking the water tube coming out of the pump.

Disassemble was a snap and I will be replacing the pump as soon as I can get the parts.

Forest

Re: Yamaha 90 2 stroke overheat?

New water pump impeller was installed and I have been to the lake twice with no more heat warnings. Thanks for the help