Mercury 40 HP 4 stroke alarm

G

grcarter

Cadet
Joined
Mar 30, 2011
Messages
9
Hi There, I have a 2004 Mercury 40 HP 4 stroker. After about 3-4 minutes at WOT I get an alarm followed by a rev limiter......I go to neutral and can apply SOME throttle but if I open it up again it will shut it down...The pee stream is strong...and only warm.
From what I can tell this may be a low oil pressure alarm?? The oil level is fine and it looks clean. Perhaps the wrong weight??

The engine is fitted with a 15 P prop. Just changed to it...runs about 5400 at WOT....is this an issue???

I live in Charleston, SC...the water temp is 88 and the ambient as you all may know is in the high 90's...
Any thoughts???
 
M

Maxz695

Guest
Re: Mercury 40 HP 4 stroke alarm

is the alarm a beep beep beep or a long BEEEEEEEEEEEEEEP? This will let someone know weather it,s the oil alarm or the temp alarm. Float sensors in the oil tank are notorious for going bad and may be the problem. I have an Oil injection pump from a 1997 oil injected 40 HP 4 cylinder Message me if it comes to that. Cheap. As Stated in My PM check the shaft on the oil pump if it turns out to be the oil alarm
 
G

grcarter

Cadet
Joined
Mar 30, 2011
Messages
9
Re: Mercury 40 HP 4 stroke alarm

Thanks for the reply.
The alarm is a BEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEP...solid tone.
This is a 4 stroke.
I have read that this engine has 3 alarms.
1.Temp
2.low oil pressure. (with rev cut)
3.something else.....
SO...with the associated rev limit while the alarm is sounding...I thought it was the low oil pressure..??

What do you think??

This think runs Perfect except for this alarm ......and rev limiter...
 
J

Jake.

Seaman
Joined
Jul 1, 2011
Messages
73
Re: Mercury 40 HP 4 stroke alarm

Solid beep is the overheat alarm. Rev limiter is your engine going into safe mode.
 
G

grcarter

Cadet
Joined
Mar 30, 2011
Messages
9
Re: Mercury 40 HP 4 stroke alarm

Thanks for the thread.
This is a 4 STROKE...there is NO oil injection.....

SO..I think we are not on the same page..........

Temp alarm...does that shut the revs down to idle speed???
I have read that this is the low oil pressure...4 stroke........????

After I go back to throttle it will run at 4200 RPM without the alarm.....but at WOT it does...
The water stream out the back is only slightly warm to the touch even at speed...the stream is STRONG..
 
G

grcarter

Cadet
Joined
Mar 30, 2011
Messages
9
Re: Mercury 40 HP 4 stroke alarm

OK...so if it is the temp sensor...is it plausable for it to go off AND have a solid stream that is not hot??

Is the info in the other thread valid here? Meaning that it goes off at 190 degrees and shuts off at 175??
 
M

Maxz695

Guest
Re: Mercury 40 HP 4 stroke alarm

Depending on your thermostat temp The do sell different tempatures but I,m thinking as long as your not overheating to change out the sensor itself. They are none to go bad. You can do that test. There should be no reading until it hits the overheat temp. meaning if it goes off before then it is shorting out. Unless there is some kind of restriction at the RPMs you specify thAT WOULD RAISE IT to that temp then I can see it being the sensor failing
 
M

Maxz695

Guest
Re: Mercury 40 HP 4 stroke alarm

Ok gotta forgive me I spent all day yesterday replacing my crankshaft and rebuilding the engine for the test ride today all when pretty good. Your alarm isn,t going off until you reach 4200 RPM meaning the sensor seems to be OK. A weak impeller will put out fine and slip at higher RPM This will get worse if this is the case. You may have sand of debris inside the exhaust port that flows fine then covers the jacket ports under pressure restricting the flow of water necessary to cool the engine properly at them RPMs. I hope this is not the case Back flushing may help but from what Ive seen taking off the exhaust port and possibly block base plate is the only way to get to the source for larger debris
 
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