Guardian warning above 4000 RPM

[coltool]

I have the 5.0 MPI engine that will run all day under 4000 RPM but the water pressure is showing only about 6.5 PSI. Above 4000 RPM I get a guardian warning which I believe is due to low water pressure. The engine only has 124 hours and the impeller on the pump was recently replaced, Engine temperature is showing 161 degrees. So either I have a pump issue or it is the pressure sensor. I read that I can possibly use the AC Delco pressure sensor but not certain. As folks have noted the Mercruiser part is significantly more expensive. I also see I may be able to install a "T" and gauge at the sensor location to compare what it is reporting to actual. That seems like an easy test as the sensor is readily accessible-not so much the water pump.

 

[Espos4]

It may be time for a new pressure switch.

Another thought. Was the old impeller removed intact? Or were there pieces missing?

If pieces were missing, were they retrieved? Did the cooling system get back flushed to remove them?

Has the transom hose been removed to check for “bravoitis” ?

Corrosion can choke down the opening in the transom, restrict water supply to the pump and give you low pressure.

 

[coltool]

It may be time for a new pressure switch.

Another thought. Was the old impeller removed intact? Or were there pieces missing?

If pieces were missing, were they retrieved? Did the cooling system get back flushed to remove them?

Has the transom hose been removed to check for “bravoitis” ?

Corrosion can choke down the opening in the transom, restrict water supply to the pump and give you low pressure.

The impeller was intact and quite frankly still quite serviceable. Still looked new. Not familiar with "bravoitis but the boat is used in fresh water. But worth a check. I will do the "T" and a separate pressure gauge test first but good to know about the hose. The low pressure is new as the problem did not exist until recently so possibly an obstruction or as noted bad sensor. Thanks for your post.

 

[Jimmy Buoy]

Do you have access to a Rinda Scanner? It would show the raw water pressure real time as you run. An alternative you could consider is adding Mercruiser's Vessel View Mobile to your boat. Its a device that is easily connected to the engine's ECU and brodcasts all engine vital parameters via a Blue Tooth Signal. That signal can be displayed on any smartphone or tablet once Merc's VVM app is downloaded.

 

[highslice]

Do you have access to a Rinda Scanner? It would show the raw water pressure real time as you run. An alternative you could consider is adding Mercruiser's Vessel View Mobile to your boat. Its a device that is easily connected to the engine's ECU and brodcasts all engine vital parameters via a Blue Tooth Signal. That signal can be displayed on any smartphone or tablet once Merc's VVM app is downloaded.

I installed this 4 years ago and absolutely love it. But if the sensor is bad, VVM will get a the same bad readings, as will the Rinda. I would go with the T and use a mechanical gauge to verify. But I can't over emphasize how awesome the Vessel View Mobile is.

 

[Scott215]

What kind of out drive is it

 

[aerobat77]

Check the neutral switch on your drive