Guardian Mode?

[BryannPam]

2005 Mercruiser 350 in a 2005 Regal boat. All was running well, last weekend, about 30 down the lake when alarm sounded, motor coughed and by that time I had already reduced throttle to idle and slowed down. At idle after a few seconds, alarm went off. Tried to take off, and about 1000 RPM, alarm sounded, motor coughed and back to idle we go. Hot day, so we anchored and kids swam while I was checking fluid levels and such. All was full or at the correct level. Bout an hour later, started right up, went to throttle up and about 1000 RPM, alarm, cough and back to idle. Not many folks on the lake Sunday evening, and we didn't have far to go so at idle speed, we motored back to the dock, bout an hour. As long as was we were at idle speed, all gauges were good, and motored right along. Ideas ?

 

[alldodge]

What is the motor serial number?

A solid alarm can be caused by
Overheat
Low water pressure (most probable cause)
Overspeed (Motor thinks its in neutral, starts at 3500 rpm)
Low oil pressure
Port or starboard exhaust overheat (catalyst motor)

The best way to find the issue is with a scanner but the most probable cause for this issue is the water pressure sensor which is mounted on the power steering cooler

Hey GA_Boater want to move this to the mercruiser section

 

[alldodge]

If you haven't changed your impeller do that first

 

[BryannPam]

Double post

 

[BryannPam]

Thank You for your replies. I'll get back to you on the motor serial number, it's at a friends dock on a lift currently. I had also read about the water pressure sensor, anyway to test the sensor without the scanner? First year boat owners, so learning as we go. Impeller was changed July 17. It need to be done again? Also, boat was left in the water at the friends lift. Could have it sucked up stuff?

 

[alldodge]

Thank You for your replies. I'll get back to you on the motor serial number, it's at a friends dock on a lift currently. I had also read about the water pressure sensor, anyway to test the sensor without the scanner?

In most cases no. That sensors has given more Merc customers problems ever since it was installed. While it is nice to know if there is a problem, the sensor just does not last long.

First year boat owners, so learning as we go. Impeller was changed July 17. It need to be done again?

Not usually, they normally last 2 to 3 years. Now if the impeller came apart before replacement, then the cooling system needs to be back flushed and checked for left over pieces which can clog things up

 

[BryannPam]

Thank you again for your fast reply. Is the sensor something someone with limited engine skills could change, and are this boat engine specific meaning year model size and such?

 

[alldodge]

Thank you again for your fast reply. Is the sensor something someone with limited engine skills could change, and are this boat engine specific meaning year model size and such?

It is easy to change, if (the bog IF) its the water pressure sensor. Its mounted on the power steering cooler which is on top the rear of the motor in a tube which was rubber hoses attached to both ends. Part number is 8M6000623 and is expensive. Cost is around $150 from Merc and is highway robbery, but can be found by searching on the part number for under $30 at other sites

 

[BryannPam]

Thank You Alldodge. Will pick up a sensor and change it out this weekend. Keeping our fingers crossed.

 

[BryannPam]

Well, Water Pressure Sensor is not the issue. Was able to get it to about 2600 RPM, almost on plain when the alarm sounds, guardian mode again.

 

[alldodge]

What is the display saying?
It could be your neutral switch on the shift plate

 

[BryannPam]

We dropped it off at the stealer ship, was oil pressure sending unit. But, found an port exhaust manifold leaking, this something a novice can change ? They want $500 to change 3 gaskets . . ?

 

[alldodge]

Yes, no issue with changing exhaust gaskets. What I would do first is make sure it is leaking, should be visible or could fell it.

If this is the case, get some 3/8-16 all thread rod at the hardware store, about 1 foot and cut into 2 six inch pieces. Going to need a torque wrench which can probably use loaner program at auto store.

Torque specs are

Bolt, Exhaust Elbow To Exhaust Manifold 33 ft lb
Bolt, Exhaust Manifold To Cylinder Head 25 ft lb
Bolt, 6 Inch Riser To Exhaust Manifold 33 ft lb

No need to replace a 3 if its only the manifold. Remove the 2 outer bolts and install the all thread rod. Then remove the rest of the bolts. Now slide the manifold and risers off the all thread rod (it heavy)

Look at both surfaces and if good, replace gasket and reinstall manifold. Snug up all bolts a little until you can remove the all thread and reinstall the outer bolts. Now torque the bolts from the inner most ones to the outer in 2 passes. Do 20 ft lb, then do 25 ft lb

If its just the riser gasket only do it