overheat after open throttle??

[oxbeast1210]

1989 Evinrude tracker xp pro 150 hp model : te150slcem

thanks to your guys help ive been able to get me outboard almost to the point that it works just right. The issue I'm having now is that my overheat alarms goes off after Ive been at open throttle seems to be fine while at wot but as soon as i start to throttle back my overheat alarms sounds i also noticed that the water coming from the tale tale alternates between really hot and to about the temperature of the water in the river about every 15 seconds. SO far i have replaced both poppet valves ,both overheat sensors and wiring, both thermostats , and cleaned out both of the water jacket passages which seems to have helped some but my alarm is still sounding Tuesday i will be taking it in to get the water pump replaced i was told by the last owner that he replaced them about 3 months ago but i want to make sure a new one is in there and in there right . I also have an issue with my tachometer the first ten minutes i am in the water it works great but after that it just shoots down to 0 and stays there i don't know if it could possibly be related to the overheat but i figure the more in for the better help i can get
please if you have any thoughts on what else it could be please let me know

thank you

 

[emdsapmgr]

Re: overheat after open throttle??

You can also get a constant horn if the vacuum switch on that engine senses 7.0 inches of vacuum. You need to determine if the horn is related to either of the head temp switches (true overheat) or if it relates to the vacuum switch (fuel restriction.) I'd temporarily disconnect the one, then the other head temp switch and see if you still get a horn. Then check the vacuum switch. Also, could be a defective horn.... A laser temp gun will easily attest to the true head temp when running. The tach is driven by the alternator pulse signals that come from the rectifier/regulator. Possible it quits working when it the engine heats up to normal operating temps. You may see that the voltmeter in the boat is only reading normal battery voltage (12.5 volts) when the engine is warmed up. If the rectifier/regulator is working properly, you should see 13+ volts after run for a while.

 

[oxbeast1210]

Re: overheat after open throttle??

Ok thank you i will try what you advised by disconnecting the alarm senders one at a time wish i would had thought of that last night ill try it after i get the new water pump installed I'm scared to make the alarm go off again because of the fear that it might be overheating and that i will cause damage
i also ordered a laser thermometer seems like a must to take with me every time lastly where is the vacuum switch that you are talking about?
o yeah also do you know if it is normal for the tale tale to alternate between really hot water and cool every 15 seconds or so?
thanks again

 

[emdsapmgr]

Re: overheat after open throttle??

The vacuum switch is on the port side of the engine, aft of the starter on the side of the engine. Possible the variance in the telltale temp is as a result of the thermostats cycling open and closed. Those stats act like a water restrictor at idle and may temporarily close to keep water in the block to insure it runs warm enough, considering the usually cool/cold water coming into the block from the lake.

 

[oxbeast1210]

Re: overheat after open throttle??

ok that makes sense but if the motor is overheating should the stats be closing and opening would they not just stay open ? This is making me think more and more that it is a fuel restriction issue like you had stated. I found a pretty bad kink (i know shame on me) in the fuel house after the squeeze bulb i did not notice it since i was not really looking for fuel issues at the time i was sure it was an overheat. could that kink have been causing the alarm to go off? . Anyway I have ordered a laser thermometer and will be changing the water pump tomorrow what temperature should my outboard be running at at open throttle i cant find it in the clymer manual that i have . lastly I want to thank you for helping me out I am in the military and have a hard time catching up on my outboards maintenance when i am home, your help makes such a huge difference in what i can get done !!

thank you! and i mean that!

 

[emdsapmgr]

Re: overheat after open throttle??

Sounds like you may have found your problem. Sometimes it is the simple things that cause problems. Thanks for all your efforts in the Service!