High Temp Alarm 1998 225HP EFI

[bajabum]

After running for about 45 minutes at both idle and on plane, the high temp alarm (according to visual indicator) sounds intermittently. The temperature gauge indicates 140 degrees, the same as the other engine. If the engine is turned off and the ignition turned back on again (engine not started yet), the alarm sounds consistently at 2 second intervals with alternating high temp and low oil warning lights indicated. If engine is then started, the intermittent high temp alarm situation occurs again. The engine also seems to have only about 60% of it's power when attempting to get on a plane after the engine gets in this mode. After engine is off for an hour, the engine is still in this mode.

 

[KCLOST]

Re: High Temp Alarm 1998 225HP EFI

An intermittent alarm, "beep,beep,beep" is an indication of an oil injection problem...Not an overheat condition.

 

[rodbolt]

Re: High Temp Alarm 1998 225HP EFI

hello<br /> the ECM has detected a fault with the alarm system.<br /> the beep beep then oil visual then hot visual. the last time I fought that problem was on a carbed version. turned out the stbd temp leads were to close to the high tension plug wire and would trigger a malfuntion alarm occasionally.<br /> rerouted the wires and the problem went away.if it persists it will be time to take it to some one with a good electronics background and a knowledge of the merc alarms.<br /> good luck and keep posting

 

[bajabum]

Re: High Temp Alarm 1998 225HP EFI

Thanks for the input guys. KLOST, when you say oil injection problem, are you referring to the injection pump itself, or something related to the float switch in the oil tank? I don't think my engine directly monitors the oil injector pump. I guess when this happens again, I can disconnect the oil tank float switch (after verifying the oil tank is full, of course) and see if the problem goes away. <br /><br />rodbolt, I'll check the routing of the coolant temp sensor wires. I already tried swapping the coolant sensors between the engines and the problem stays with the engine.<br /><br />Thanks again.

 

[KCLOST]

Re: High Temp Alarm 1998 225HP EFI

It could be either... The pump or the float...<br /><br />I believe your engine uses comparing voltage from the #4 coil to ensure the pump is working. But I'm not really sure on that...<br /><br />Maybe someone else can jump in and help!!!!

 

[bajabum]

Re: High Temp Alarm 1998 225HP EFI

I'm now suspecting an intermittent short in the coolant temp sensor harness that leads to one of the ECM's. I simulated this situation by grounding the coolant temp sensor input to the ECM's and the failure symptom matches: alternating hi temp & low oil visual alarms when ignition is turned on followed by hi temp alarm when engine is turned on. I checked the routing of all wires as suggested and it's identical to the good engine. When the intermittent temp alarm sounded on the water, I disconnected the oil tank sensor for a short while and the problem continued to occur. At this point I have swapped coolant temp sensor, MAP sensor and air temp sensor between engines and the problem continues to occur. I am considering swapping ignition and fuel ECM's between engines also. I have pulled off all connectors between coolant temp sensor and ECM's and they all look OK with plenty of dielectric grease on ECM connector pins.<br /><br />Does anyone have additional information on the oil pump sensing that was mentioned earlier? I haven't been able to find any documentation on this.<br /><br />Thanks

 

[bajabum]

Re: High Temp Alarm 1998 225HP EFI

My apologies for not updating the results of this troubleshooting project sooner. After several more weeks of intermittent alarm problems I discovered that when the cowling was in place, one of the wires in the harness was chafing against the engine block and had exposed a tiny portion of bare wire causing a short. This would only happen when the cowling was in place and the alarm condition would go way when the cowling was removed for troubleshooting. The problem was fixed by routing the harness properly and supporting it with cable ties after repairing the wire.<br /><br />Thanks for all the input on this problem.

 

[jfuentes1015]

Re: High Temp Alarm 1998 225HP EFI

The temp gauge on my 225 efi merc, always shows at 220, however the engine is not hot at all, already replaced gauge, and thermostats, what could be happenning?