Hot light 98 50hp 2cycle uhhhhg!!!

[Seanmarty93]

I hope someone can help me. I keep getting the hot light and buzzer on my Johnson outboard. I recently bought the boat from a friend who was frustrated with the boat as he said after a couple of trips to the shop, it was deemed "fixed" but when he got on the lake it would hit about 1/4 throttle then fall on its face. I knew it had a problem when i bought it but it had good compression so i rolled the dice. Thanks to this site, i was able to figure out it was stuck in S.L.O.W. I took the water pump apart and found 2 of the three cogs had broken off the impeller and were laying inside of the waterpump housing. I bought a repair kit and replaced all components of the water pump. I pulled the thermostat and noticed a couple of small chunks of rubber from the impeller in the t-stat housing. I removed them and put the new thermostat in. Now, when I start the motor, I immediately get the hot light and buzzer. When I hit WOT the light goes out. I can run WOT with no issues, but once I throttle down, the warning light and buzzer alarm again. What's confusing me the most, is if my boat sits overnight and is completely cool, I can back the boat into the water, not start, but just barely engage the starter, and immediately the hot light and buzzer sound off. How can it be hot if i haven't even started the motor? I did however, remove my thermostat, made my own fittings that allowed me to hook my hose into the thermostat housing with a tight seal, removed the lower unit, and backflushed the motor for several minutes. I also "pinched" the hose by folding it in half, then quickly straightening it to give the water some extra pressure or surging action. However nothing came out. You could pressure wash a mud truck with the water coming out of the tell tail when the motor is running. The motor doesn't feel overly hot to the touch when the hot light comes on after throttling down, and, why is it buzzing hot before the motor has even started? I unplugged the temperature sensor to see if that would make a difference and it didn't. I also pulled the temperature sensor and got no continuity between sensor end and the end of the wire, so i assume the sensor is not "stuck on". So what could be causing the hot light and buzzer to continue to alarm? Is there another sensor I'm not aware of that could be shorting out? I'm extremely confused. Especially since it shows hot before the motor even runs. ( and Im not talking about how all four lights come on when you first turn the key on...lol) any input or advice would be GREATLY appreciated!!!!! I'm at the point where I'm ready to tear the motor apart to make sure there is no impeller pieces clogging a water passage. I just want to rule everything else out before I do that!!!!!!!

 

[ondarvr]

Those System Check tach's had issues with the alarms sounding for no reason, mine did the same thing, turn on the key and you get a constant over heat alarm. If the rest of your cooling system is working correctly the only solution is a new tach.

 

[Seanmarty93]

Thanks for the response. My hot light doesnt stay on. It comes on along with buzzer everytime i start the motor. Buzzer sounds for about 10 seconds then stops, but light remains on. Then, when i take off at WOT it remains on for about 10 seconds then goes off until i throttle back down. Then both light and buzzer come back on. It makes me think the motor is getting sufficent water supply at higher rpms, and that I may have a piece of rubber from impeller clogging a passage somewhere. What's confusing me is why the alarm sounds immediately when started cold. Also, i unplugged the temp sensor to see if alarm still sounds and it does. So do you feel im safe to assume the warning system is faulty, or is there another sensor that Im not aware of that would trigger alarm. Very confusing.......Thanks again!!!

 

[Seanmarty93]

Also......wouldn't/shouldn't the S.L.O.W. kick in if motor was truely warm as it was doing before i repaired water pump? Just another piece of the puzzle that is confusing me.

 

[Seanmarty93]

Anyone have any other suggestions or experience the same problem?

 

[ondarvr]

You may have a couple things going on.

There is a different system that bypasses the thermostats at higher RPM's, so running hot at low RPM's and not at higher RPM's is very possible, The thermostat controled portion could be plugged or have another problem.

Those tachs have issues that can be random, they don't supply reliable information once they start to fail, so buzzers, lights, RPM's, oil level, etc can be inaccurate. The buzzer should only sound for a couple of seconds when you turn it on, this is to audibly show that it still works, no other reason, if it stays on for 10 seconds something is wrong with it. I had 2 of them go bad.

The only way to tell is to actually test the motor with other gauges.

 

[oldboat1]

might start with an infrared temp. gun -- check temp at the top of the head and get a number for a benchmark (or numbers -- at idle and at higher rpms.) It sure sounds like the gauge -- can't speak specifically to that motor, but had a much older Evinrude that did something similar after its only overheating episode. It was the switch. I was a little uncertain of it, and went instead to a replacement OMC gauge with a cylinder head contact sensor.

 

[Seanmarty93]

Thanks everybody for your input. I really do appreciate your time and knowledge. I will pick up a heat sensor gun. I believe harbor freight has one for fairly cheap. I really feel as if its a faulty tach the more i research it. I just wanted to make certain there wasnt more than one sensor that would trip the hot warning. The fact it gives the hot warning before the engine is started raises my suspicions the most that it really is not overheating. The only thing that makes me worry is the way the alatm sounds after coming off W.O.T.. Thanks again fellas!!!!!

 

[jakedaawg]

Do you know any one with a "known good" system check guage? Plug it in and see. I might also suggest checking the tan wire for intermittant shorts to ground by isolating sections of the tan wire and ohming to a ground while wiggleing and pulling gently. After all the bad compression readings on here lately I would be careful about trusting an HF temp gun.

 

[Seanmarty93]

Buddy says he has temp gun. So ill try that. I dont know anyone with good gauge i could try. But once again i feel like it almost has to be a bad gauge because as siin as you start the motor up it immediately buzzes and hot light comes on. The motor hasn't even began to get warm. Does anyone know if there's any other sensirs on that motor, besides the temp. sensor/switch that causes the alarm and hot light to come on? Thanks!!!!

 

[oldboat1]

temp gun can also be useful for troubleshooting electricals, btw. Shorts are hot spots. Need some benchmark tests, then look for changes.

 

[ondarvr]

Pull the high temp sensor out of the motor and test it on the stove in a pan of hot water. See at what temp it makes contact. The thermostat opens at about 140*, the sensor makes contact much higher than this (sorry I can't remeber the exact temps for each right now), so if it makes contact at lower than 140 the sensor could be bad, if not it should be the gauge. Use a digital multi meter and test for continuity. Follow the tan wires to the sensor on the head.

 

[tblshur]

just a comment, dosent the vro , if it has one , sound the same alarm ?:joyous:

 

[ondarvr]

just a comment, dosent the vro , if it has one , sound the same alarm ?:joyous:

Yes, but it isn't constant.

 

[Seanmarty93]

Thanks for the replies fellas. What is a VRO? Thanks!!

 

[ondarvr]

VRO, is the oiling system, do you pre mix, or is there an oil tank? The alarm will beep if the oil level is low in the tank, or if it senses no oil flow.