7.4 mag gives double beep alarm at 3000 RPM...?

[mysticCrunch]

Im having the same issue with my 7.4 mag in my sea ray Engine temp a solid1 60/ oil press rock steady 50 psi lube oil bottle ok at 1400 rpm I can drive around all day but as soon as I go over 3000 rpm I get the same double beep alarm the revs are not limited but the alarm sounds double beep until I turn the key off ? HELP Don't want to mess up 7.4 mag with only 60 hrs on it HELP!!!!

 

[mysticCrunch]

Hi, I'm having what seems to the same issue with my 7.4 mag as what the following member is having in another topic linked here, https://forums.iboats.com/forum/engi...ev-limit-issue

My sea ray engine temp a solid160*.... Oil pressure is rock steady 50 psi.... Lube oil bottle seems ok... At 1400 rpm I can drive around all day but as soon as I go over 3000 rpm, I get the same double beep alarm, the revs are not limited but the alarm sounds the double beep until I turn the key off ?

Please help, I don't want to mess up this 7.4 mag with only 60 hrs on!!!!
Engine codes where checked by certified mercruiser mechanics.... They replaced the water temp sensor on the thermostat housing but it still did not solve the problem....Any advice to go from here? Thanks....

 

[tpenfield]

Got a serial number for the engine? Is this a carb or MPI Magnum? I assume MPI based on the code reading, but want to be sure.

 

[mysticCrunch]

Thanks Ted ILl work on getting the serial # Its a 7.4 ltr magnum mpi mercruiser 1998 that was just rebuilt and has only 50 to 60 hrs on it the alarm only comes on when the the boat comes under load {on plane ] and just over 3000 rpms It will not go off until I turn the key off ? The alarm will not generate out of the water I had some mercruiser certified mechanics try to read the engine codes while out of the water with a mercruiser scanner and there were no engine codes. Thanks for the help

 

[alldodge]

what octane fuel are you using?
You can make a code reader with a resister LED (radio shack) and a paper clip

 

[tpenfield]

I got tired to troubleshooting my MPI engines 'in the dark' and got the Rinda engine diagnostic software. I would go around the engine and check the connectors to each of the sensors. Release the tab and then re-connect each one.

You know the ECT is OK, since it was replaced with no difference. You have the MAP and the IAT sensors on the plenum, and the IAC and the TPS under the throttle body.

Other than that it is a matter for reading codes when the engine is doing the beep thing. We are talking a double beep every minute or so (right?)

 

[mysticCrunch]

Im pretty sure the timing is spot on its a brand new motor with only 50to 60 hrs on it it purrs like a kitten at 1400 rpms I will check and replug all the sensors I just got back from the mechanics who rebuilt this motor and as I described the double constant beep they feel it might the throttle position sensor since it does not stop beep under 3000 rpms until I turn off the key Im gong to replace the tps and go from there thanks much !!

 

[tpenfield]

I just replaced the TPS on one of my 7.4L MPI engines . . . You could test it with a volt meter and the ignition on, but engine not running. Does the engine idle down to 600 RPM once warmed up?

 

[alldodge]

double constant beep

Can you expand on what you mean by this?
Is it a double beep every minute or so, constant beep or something else?

 

[mysticCrunch]

repeating double beep constant until the key is turned off

 

[alldodge]

2 beep, slight pause, 2 beep and repeat

what octane fuel are you using?

 

[tpenfield]

The only thing even close to that alarm pattern that I could find is on the MEFI-3


"Beep alternates on for one second, then off for three seconds with a soft alarm below 3000 RPM and a solid horn above 3000 RPM"

Possible causes are listed as:

Oil pressure
Engine Coolant Temperature (ECT)
Drive lube low
Sensor fault

Keep in mind that the temperature that you are seeing on the gauge at the helm is NOT the same as what the ECT is seeing. They are 2 different senders.

I'd say since your oil pressure and coolant temperature are normal, that you either have low outdrive oil or a sensor fault.

 

[scoflaw]

My boat is a MEFI 3 and I can state as a fact that an overheat and low oil pressure will give a solid alarm irrelevant of RPM.
Only time I hear the 2 beeps is initially turning key on.

 

[mysticCrunch]

Thanks I believe you are correct the alarm is not a single solid continuous tone it's a double beep that sounds after I go over 3000 rpm when I initially turn the key on I get a solid 3 second tone then it clears With that being said im ruling out water temp and oil press My next move is to replace the throttle position sensor and go from there.

 

[tpenfield]

You are probably hearing a sensor fault alarm . . . loose connection or faulty sensor. If you replace the TPS, you may need to be sure to adjust the Throttle Position Sensor to 0% throttle when you install it. I believe that will give a voltage reading of about 0.55 - 0.50 volts on the output wire.

I installed a new TPS on my 7.4 MPI (MEFI-1) last week, and the initial setting upon installation was 3% throttle (about 0.74 volts), which resulted in a high idle of about 1500 RPM. Once I figured things out, I was able to adjust the throttle plate stop and the TPS itself to get to the 0% throttle setting, and a nice 600 RPM idle speed.

 

[achris]

Instead of just 'throwing parts at it' have you considered putting a voltmeter on it and checking that it's adjusted correctly. Replacing sensors because 'it might be this one' gets expensive, quickly. Easier and quicker to find the problem and fix just one item. Since you have no codes set, you can rule out most sensor failures off the bat.

Chris......

 

[tpenfield]

To Chris' point, I bought the software to diagnose and analyze the MEFI data (Rinda/Diacom software). I think it has paid for itself a couple times over already.

Also for many of the sensors, there is a GM equivalent of the pricey Mercruiser packaged part.

 

[mysticCrunch]

Im just going to replace the tps if that does not solve the issue It's going back to the cert mechanics who installed it . This motor only havs 50 to 60 hrs on it so every sensor should be new during the rebuild

 

[mysticCrunch]

My boat is a MEFI 3 and I can state as a fact that an overheat and low oil pressure will give a solid alarm irrelevant of RPM.
Only time I hear the 2 beeps is initially turning key on.

it's not a solid tone its a double beep after going over 3000 rpm

 

[mysticCrunch]

Can you expand on what you mean by this?
Is it a double beep every minute or so, constant beep or something else?

once I rev the engine to get the boat on plane a double constant beep stays---- on even after I pull the throttle back beep ----- beep and it will stay on until I turn off the key . I can restart the engine and there is no more alarm I could drive to the moon and back the oil press is 50 psi and the water temp is 160 runs great but as soon as I try to go back over 3000 the alarm comes back on I replaced the water temp sensor but that did not solve the issue. Im going to try to replace the throttle position sensor and if that does not work its going back to the cert mechanics who installed the engine.