2005 mercury 4 stroke efi 30hp alarm

[KOBELKA2277]

hello, I have the above motor. After 5 minutes of driving at full speed the motor alarms. A steady alarm. after slowing to idle it goes away after a minute. I changed the water pump impeller and the thermostat but it still does it. any ideas?

[oldrock]

seems this is a problem with alot of owners. I have a 2001 50hp 2 stroke and experiencing the same thing. No answer but I changed the impeller and get strong stream. Also when alarm goes off, I checked the water stream coming out and it was only slightly warm. IF my compression checks out ok, I am going to change out the sensor and see if that might be it. Also I read on another thread that changing out the fuel line connector might be it.

[oldrock]

so did you find the solution to your problem? If so, what did you do?

hello, I have the above motor. After 5 minutes of driving at full speed the motor alarms. A steady alarm. after slowing to idle it goes away after a minute. I changed the water pump impeller and the thermostat but it still does it. any ideas?

[Dunaruna]

There are 5 possible causes for a continuous alarm, overheating is just one of them.

While the alarm is going is there a good stream from the pee hole?

[oldrock]

what are the 5 causes? I'm still trying to sort out my alarm issue. My engine runs great and idles smooth, etc. but when I run at higher RPMs, after a couple minutes, I get the continuous alarm. Stream is strong and does not feel hot at all when alarm is going off. I can drop to idle speed and within about 15 seconds alarm stops. I've changed the impeller and the hose/bulb/connector using genuine merc parts. Didn't make any difference. THinking next thing to try is the thermostat although I am just guessing.

[Florida Fisheagle]

Dunaruna, Mine does not show any signs of over heating, no steam and the engine is not hot when you pull off the cover, but it has never had a good stream from the pee hole. Could water in the fuel be causing this?

[Dunaruna]

The pee should be steady, strong and warm to touch (not hot or cold). If the stream is not strong, you can back flush the pee hole with garden hose pressure in the hope of dislodging any foreign material. If that fails, thermostat and pump check.

The 5 alarm conditions are (continuous alarm) -

Overheating (see above)

Low oil pressure (revs will be limited to 2000)

Over-revving

Battery voltage out of range

Coolant sensor failure

The alarm has set a code, need to get the codes read by merc. Until then we can only speculate.

[Dunaruna]

Dunaruna, Mine does not show any signs of over heating, no steam and the engine is not hot when you pull off the cover, but it has never had a good stream from the pee hole. Could water in the fuel be causing this?

Water in the fuel will cause misfire, rough running and no start. But not overheating.

[KOBELKA2277]

Hi again,
I have found out that I can run no problem 3/4 throttle it only alarms on full tilt and only alarms after 10-15 minutes
I have changed the impeller, excellent flow warm to the touch, still alarms.
I have changed the thermosstat and it still alarms.
It cant be the oil pressure as it does not limit the rpms
Battery seems good
It doesnt over rev as I have the same engine on a duplicate boat with the same prop and have no issues.
If I wanted to swap a coolant sensor from another engine would that be hard to do? Where and what would it look like. Thanks
We will figure it out one way or another

[honestcharlie56]

just throwing it out, maybe oil and filter, but seriously it sounds like and over rev, get a prob with a higher pitch and see if it goes away, most boat stores will let you "test" a prop, or at least the store i work at does, if you were overheating you would know it pretty quick.

[Martian]

It doesnt over rev as I have the same engine on a duplicate boat with the same prop and have no issues.
r

Doesn't over-rev because your other boat has the same prop? Thats a maybe.

What is the recommended load range for you motor/prop combination.

Martian

[KOBELKA2277]

Hi,
Not a mabye. Im saying I have two identicle boats with 2 identicle props on 2 identicle outboards with identicle loads...Me. One has the alarm, one doesn't. It cant be over revving. I just wondered if anyone knew where the coolant sensor is and I would swap one for the other and see if the problem switches motors.
Thanks

[KOBELKA2277]

Hi There,
Thank you for all your help. I recently checked out the prop on the boat in question and even though it was the same make and pitch as the identicle other boat the prop wasnt the same . I switched props and the problem went to the other boat. Apparently the problem prop was causing the rpms to be too low causing the overheat alarm problem. A new prop and the problem went away.
Again thanks to everyone.
Dave

[Craigcat]

I know I should start a thread, but am in a BIG hurry to get help! I need a factory Service Manual for a 2006 30HP EFI. Its running in limp mode!

[Mr. Florida]

My 25 HP Bigfoot 4 stroke is doing this very same thing. I have changed impellers, T-stat, temp sensor and ECM, did a backflush through the t-stat hole. Still does it. I may change the prop (13P) as he did as it will not make it to 5500 rpm, like it used to.

KOBELKA2277, do you have a tach on your boats?