Engine Overheat buzzer

[TopNotch]

Just wondering if it is possible to get a false warning from the buzzer?<br /><br />All my gauges say everything is in check, Water temp, and water pressure is normal (6psi idle/12 WOT). No excessive steam when the buzzer is going off. The pisser is cold.<br /><br />(The buzzer goes off as if it were getting hot when im up over 3500 rpm, then i idle down and the buzzer stops, its not always off like theres a permanent short)<br /><br />FYI: its a 1986 Evinrude V6-150hp. THANKS IN ADVANCE!

 

[Solittle]

Re: Engine Overheat buzzer

I won't bore you with my long tale of woe but I'm fighting a simular problem with one of my 1987 OMC V4s. I have 10lbs of pressure at idle - 20 at WOT (pressure guages mounted on inside of transom)- - - real strong teltale - - - heads are cool - - - and the horn goes off after it gets up on a plane - - and stays on. Pulled the heads & have one cylinder with clear signs of detonation (possible water injestion) or ring failure.<br /><br />For you - I would suggest replacing impeller & Tstats even if you think they are OK.

 

[sparkroost]

Re: Engine Overheat buzzer

Top, sounds like your impellor is gone. 12lbs @WOT is too low. I think 20-30 is more like it.<br /><br />It's possible that your water temp sensor location and your surface head temp switch are entirely different locations. It is possible that the cylinder that has the switch in it(the one that set's off the buzzer) has the problem. Too lean a condition in that cylinder will cause much higher temps.

 

[DIRTPOORE96]

Re: Engine Overheat buzzer

HI TOPNOTCH, IT SOUNDS LIKE YOUR FUEL DELIVERY SYSTEM IS THE PROBLEM. CHECK THE FUEL LINES & HOSE CLAMPS FOR AIR LEAKAGE. CHECK THE FUEL FILTER ON THE BACK OF THE MOTOR, THE O-RING & GASKET COULD BE LEAKING IN SOME AIR. IT CAUSES THE MOTOR TO RUN LEAN & HOT. WHEN YOU BACK OFF THE THROTTLE YOU ARE GETTING LESS AIR & THE ALARM STOPS. WHEN YOU INCREASE THROTTLE IT SUCKS MORE AIR & SOUNDS ALARM FOR FUEL RESTRICTION OR OVERHEATING. THATS WHERE I WOULD LOOK. (DIRTPOORE96)

 

[TopNotch]

Re: Engine Overheat buzzer

All good suggestions! Alittle more information.<br /><br />1. I replaced the water pump last season in july.<br />2. I replaced the entire fuel line/filter/all carborator lines... Every fuel line inside the cowling 2 seasons ago. (I have seen a air leak in my fuel line and the trouble it caused, didnt overheat, but lost power at high rpms, and fixed it in a hurry)<br />3. The water pressure gauge, I dont feel as being 100%. Its new this year, but i was using it as a baseline reading, and there has been no change in normal psi. (its one of those "tap in to the pisser" gauges and run a hose up to the dash)<br />4. The temp sensor is mounted next to the stock heat warning, making contact with the head.<br /><br />Ive seen my engine overheat last year when the water pump went. And it was a similar circumstance however now there is no steam, the head feels okay. I think im going to pull the thermostats. Check all the fuel lines, clean the carbs, And put alittle extra oil in (I run the 100:1 AMSoil at 75:1). Give it a test and see what happens.<br /><br />How about those laser thermometers, If i shoot each cylinder and get a reading, it should tell me which cylinder is running hot? how much do they cost? My engine should run at 143 degrees F right? Anymore suggestions?

 

[ob]

Re: Engine Overheat buzzer

TopNotch ,You say in your first post that the buzzer "isn't always off ,like there's a permanent short." Two questions.<br /><br />1- Did this engine have VRO originally?<br />2- If you are now mixing your own fuel ,are the vro alarms disconnected?<br /><br />If the temp sensor has never been replaced on you 86' model engine ,I would recommend installing a new one.<br /><br />I'd also scrap the Amsoil at 75:1 and use the recommended TCW-3 at 50:1.

 

[TopNotch]

Re: Engine Overheat buzzer

(((What i meant was the buzzer comes on and off when i increase throttle and then idle back, repectively)))<br /><br />Yeah VRO warning harness has always been disconnected. The temp sensors are definitly original equipment. But it looks like the sensors (2) are epoxy'ed into a small holes on either side the head. As for the AMSoil, I love the AMSoil though, it smells so nice compared to regular 2-cycle oil.<br /><br />Got a question about the oil, I usually mix in a "gas caddy" (~30 gallons). I have a 50 gallon internal tank. This time around i just tossed in the oil, and paid extra to get gas at the local gas dock... If it didnt mix well to start and I burned off alot of extra oil.. Could I be running really low-mix gas now???? and thats what kickin off the overheat, as i now have less than a 1/4 tank left?

 

[sparkroost]

Re: Engine Overheat buzzer

you can try this test to check for lean condition. Take boat to water. Warm up. Get on plane, w ait for buzzer to come on. Turn keyswitch off leaving throttle alone. Remove all spark plugs and look at color and wetness.<br /><br />This might give you an indication of a lean condition in a particular cylinder.<br /><br />What is baffling is that your sensor are located at near the same location. I know the temp switch is located in a recessed hole in the head, which might make a difference.<br /><br />Have you tried to run it on muffs, hold hand on head and rev up to 2000.. and wait for your brain to tell you to remove your hand?<br /><br />You can also remove the temp switch and put in hot water with thermometer with the wires connected to a multimeter. You could see then at what temp the switch is closing. <br /><br />Just curious, what does your surface temp gauge indicate at over 3500 and under?

 

[TopNotch]

Re: Engine Overheat buzzer

Haha this is the funny part... It shows COLD at 4000 rpm, when the buzzer comes on I ease off the throttle, (buzzer shuts off within 5 seconds) I keep it at idle for alittle bit and watch the temp come up to the first line above COLD and then the temp slowly decreases back to the COLD line.<br /><br />I installed my an aftermarket (teleflex gauge) temp sending unit on one of the head bolts next to the embedded heat sensor. The head is just hot enough where I can put my hand on it, and leave it there for a few seconds before it gets alittle too uncomftable to it leave there. Thats 143 deg F right?<br /><br />Hypotheotically speaking, if one of the cylinders were running lean, would that mean a clogged hi-speed jet in the carb or something else????<br /><br />(I dont think this is the case as i acheive my max normal WOT of 5200rpm)

 

[sparkroost]

Re: Engine Overheat buzzer

hmmm... sounds like the temp switch is faulty or your sending location for the teflex is not working.<br /><br />Lean cylinder runs hotter and with more power(well up to a certian point, then falls off. You could be on the verge for 1 cylinder.)<br /><br />My surface head temp is 115-123(port/starboard). Water temp is a little less than that. Running wide open I might see 140 but for short bursts of 6000rpm I see no more than 130-135. 210-220 deg will start to evaporate spit in 2 seconds. I can hold hand on heads at idle indefinatly.<br /><br />You run this in salt? You may have buildup in the head covers.<br /><br />Another thing I thought of. I have a water temp gauge. When I shut down the engine the gauge goes up to 140-150 deg. Then as time passes it will go down all the way. All the water leaks out the block and the surface temp goes up. Does your gauge do this?

 

[TopNotch]

Re: Engine Overheat buzzer

Yeah ive never cleaned the water jacket and i do run in salt, and keep it on a mooring... so i dont get to flush it out everytime i use it.<br /><br />What would cause a lean cylinder?

 

[TopNotch]

Re: Engine Overheat buzzer

^bump^

 

[sparkroost]

Re: Engine Overheat buzzer

Did ya check heads, plugs or verify that your temp switch is working properly?

 

[Dhadley]

Re: Engine Overheat buzzer

Thats a fuel restriction warning.<br /><br />Clogged vent, crimped line, too small line, anti-siphon valve bad etc. Check the entire fuel delivery system.<br /><br />Good luck!

 

[ob]

Re: Engine Overheat buzzer

I tried going there Dhadley and he says the VRO harness is unplugged.I give up on this one.

 

[sparkroost]

Re: Engine Overheat buzzer

u da man DH and OB! I was wondering though..doesn't the VRO give a different warning tone for oil vs. the constant beep for heat?

 

[ob]

Re: Engine Overheat buzzer

Sparkroost,The earlier VROs were three wire and the alarms were as follows<br /><br />* constant steady tone - overheat<br />* tone every 40 secs. - low oil in reservoir<br />* rapid short tones - no oil from vro <br /><br />The later ones were 4 wire VROs and the alarms remained the same except for the addition of the fuel restriction alarm which was also a constant steady tone and the overheat alarm was introduced with the S.L.O.W. feature which limited rpms when a overheat was detected.

 

[sparkroost]

Re: Engine Overheat buzzer

Thanks! the only way to differentiate between heat and fuel restriction is it going into S.L.O.W.?

 

[Dhadley]

Re: Engine Overheat buzzer

The give-away is when the horn shuts off as soon (within 5 seconds) as you reduce throttle.<br /><br />If the motor was truly hot it wouldnt cool down that quickly.

 

[MadeCoolCom]

Re: Engine Overheat buzzer

You always rewire the buzzer compelty