Overheat alarm, but no heat

[EVMIII]

I have a 1989 Johnson 225 (Ser # G7461562) pushing a 25' Wellcraft 248 Offshore. Periodically while running, the alarm sounds and the engine responds by reducing RPM. The motor never stalls, but vibrates excessively above 2000 RPM. Talking to some local folks, I believe this alarm is the overheat alarm. That being said, the engine is not running hot. I can place my hand on both head covers without concern. The engine is pumping water at a steady rate (don't have a pressure gauge but it is consistently steady). I've seen outboards overheat and run hot, that is not my problem. I have the auto oil pump (think its called a VRO) disconnected and mix the oil as I fuel the tank. I know that there was originally an alarm atached to it to warn for pump failure. It does not demonstrate this symptom on any kind of regular pattern. It has happened twice, once after running approximately 5 hours and once after running 2 hours. The engine was not hot on either occasion. I shut the motor down and fished for a few minutes and it started back up and ran fine. I have taken the boat out several other times with out a problem under identical circumstance. I believe I have a faulty sensor or alarm somewhere, but have no idea how to diagnos the problem. Any ideas on where to start? All ideas will be appreciate.

 

[12Footer]

Re: Overheat alarm, but no heat

I would suspect the sender, or the wire from it is grounding to ship ground somewhere.<br />Unfortunately, being an intermittant problem, your guess is as good as mine, and the only way to be sure, is to change it out. It will show continuity to ground when it senses heat, otherwise it should show no continuity.

 

[Joe Reeves]

Re: Overheat alarm, but no heat

Guard Bum..... The 225hp Evinrude/Johnson engine (as well as some other OMC V/6 engines) incorporate a fuel restriction warning via a vaccum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.<br /><br />The fact that your engine is not overheating, and that the rpms drop drastically would indicate that your engine is starving for fuel. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures your problem. Let us know.

 

[DIRTPOORE96]

Re: Overheat alarm, but no heat

HI GUARD BUM,<br />YOU COULD BE HAVING A FUEL PROBLEM LIKE JOE SAID. I HAVE RUDY'S ALSO & THIS SAME THING HAPPENED TO ONE OF MINE. THE O-RING & GASKET ON THE MOTOR FUEL FILTER WERE DAMAGED & LEAKING AIR INTO THE CARBS. THIS CAUSES A LEAN CONDITION & THE ALARM SOUNDS AT HIGH RPM'S, BUT AS SOON AS YOU DROP BELOW 2000 RPM'S THE ALARM STOPS. I WOULD CHECK THE O-RING & GASKET TO MAKE SURE THEY ARE SEATED CORRECTLY. THEN MAKE SURE THE PRIMER BALL IS PUMPED UP & NO GAS IS LEAKING OUT THE FILTER. GIVE IT A TRY, IT MIGHT JUST STOP THE PROBLEM.

 

[EVMIII]

Re: Overheat alarm, but no heat

Thanks for the input all. Talked to my local outboard guy and he said it is a water pressure problem. He saw it run (but didn't have a pressure gauge with him) and said I clearly does not have enough pressure and the problem would only occur at higher RPMs. He also said the alarm was the same as the overheat (no water, more heat makes sense). I have a steady flow from the pee hole, but it is does not seem to be very high pressure and the pressure doesn't appear to increase with RPMs. In any case, I am changing the water pump and all components this S aturday. Ordered a high output 35PSI replacement and hope it does the trick. Does this sound like a feasible explanation? It is the easiest to fix and probably needs to be done regardless. I'll let you know if it helps. Thanks again for the info.

 

[seahorse5]

Re: Overheat alarm, but no heat

There is not a 35psi replacement pump kit. Your motor needs the 5001594 kit. There is a 5001595 kit used on the '91 and later motors with the split-line gearcase that would give more pressure in your motor, but is not recommended because it would not fill the midsection with water due to the housing design difference.<br /><br />Your motor could have sticking thermostat housings, if they are white, replace them ASAP. It could also have a kinked hose in the water valve at the throttle arm. You can also have the same symptoms if the blocking diode in the wiring harness shorts, then any type of alarm will put the motor in SLOW mode. There is a bulletin about that from years ago.

 

[EVMIII]

Re: Overheat alarm, but no heat

Seahorse,<br /><br />May be wrong about the PSI, thought the dealer said 35 PSI. Just replaced both thermostats. No detectable kinks in the waterline. Can you tell me more about the blocking diode in the wiring harness? How do I isolate it and check it? Also, do you know where I can get the service bulleten you mentioned? Any help will be appreciated?

 

[Don Smith]

Re: Overheat alarm, but no heat

Hey Guard Bum, I live over in Mobile and we have been having an algi problem. It seems this thing grows on the inside of the water jacket and insulates the walls. It would feel cold to the touch on the outside but hot on the inside. Check the output temp of the water, if it's cold. it's not carrying the heat out of the engine. Did you see any mossy type groth on the thermostats?

 

[EVMIII]

Re: Overheat alarm, but no heat

Don,<br /><br />No growth in the thermostats, just corrsion. Changing the water pump tommorrow afternoon and putting the boat back in the water Saturday. I'll give it a good test this weekend. We don't seem to be having an algea problem (any more than normal) in Biloxi. I keep my boat in the water in Biloxi Bay and haven't had any problems yet. I pull the boat about once a month an wash the bottom off, but no real growth on it. Thanks for the reply. Maybe I'll see you on the water.

 

[EVMIII]

Re: Overheat alarm, but no heat

Thanks for the responses. Changed the water pump on Saturday and found damage on existing base plate and a slipped o ring. Replaced water pump and all parts (including impeller) and ran the boat Saturday and Sunday for 5 hours each with out a problem. It appears my problem was water pressure related (my local mechanic advised the low waer pressure alarm was the same as the overheat). In any case, I am back in the water. Thanks again for the info.

 

[clanton]

Re: Overheat alarm, but no heat

This engine does not have a factory installed low water presssure alarm. The overheat sensor is only sensor in a working system that will set S.L.O.W and reduce the rpms. Great that you found the problem. The blocking diode is located 24 1/2 inches from large red connector in engine wiring harness.