briefly overheating

[7Ralph]

I have a 2016 4.5 MPI Alpha/Bravo that briefly overheats as I idle through the no wake zone. It presents like a sticking thermostat. It gets to about 180 - 190, the warning buzzer sounds momentarily until the thermostat opens and the temp drops back to normal operating level. I've changed the thermostat. Ideas please?

 

[tpenfield]

Do you have the closed cooling version (SeaCore - blue labels) or the standard cooling version (red labels)?

Which outdrive do you have (Alpha or Bravo)?

Do you have the vessel view display or Smartcraft gauges?

When the engine starts cooling itself down, are you giving it any throttle?

Has the sea water pump impeller been changed recently?

 

[7Ralph]

It's the fresh water cooling system.
Not sure if it's Alpha or Bravo.
I put it in nuetral and increase the RPM (a little) to shorten the cycle and get the beeper off sooner.
I haven't put a impeller in yet. It's next on my list but I don't like to throw parrts at a problem.
I saw somewhere about a by pass valve in the thermostat housing that could be clogged. It sounds like a reasonable presetation of my problem but I've never heard of it. (Boat is 90 miles away or I'd check it out.)

 

[tank1949]

NOT real familiar with 4.5 MPI, I have only worked on Chevy V8s/carbureted. However, with a friend at helm and motor ON, wiggle temperature sensor wires and see if there is any temperature gauge change. Time to pull risers and test them, if salt water used. With a friend at helm switch, you should be able to disconnect hose going into riser from pickup for a short time and see if water is coming from OD to motor via impeller (if Alpha drive). If Bravo, with a friend at helm switch, you may test in a similar manner for water restriction in transom assembly (Bravo-itus) that will require installing a kit. Pull hose from transom assemble going to PS heat exchanger and check for water flow. Are you sure that you installed thermostat correctly?

 

[tpenfield]

It's the fresh water cooling system.
Not sure if it's Alpha or Bravo.
I put it in nuetral and increase the RPM (a little) to shorten the cycle and get the beeper off sooner.
I haven't put a impeller in yet. It's next on my list but I don't like to throw parrts at a problem.
I saw somewhere about a by pass valve in the thermostat housing that could be clogged. It sounds like a reasonable presetation of my problem but I've never heard of it. (Boat is 90 miles away or I'd check it out.)

OK, post a picture of the engine 9if you have one handy) for verification 'fresh water cooling' often refers to closed cooling, but just to be sure.

Also, you will need to know if you have the Alpha outdrive or the Bravo outdrive, because the impeller is located in a different place.

Also, is the boat used in salt water or exclusively fresh water?

 

[ROY WILLIAMS]

I have a 2016 4.5 MPI Alpha/Bravo that briefly overheats as I idle through the no wake zone. It presents like a sticking thermostat. It gets to about 180 - 190, the warning buzzer sounds momentarily until the thermostat opens and the temp drops back to normal operating level. I've changed the thermostat. Ideas please?

the impeller is around 2-3 yrs .....outdrive impeller ...

 

[7Ralph]

NOT real familiar with 4.5 MPI, I have only worked on Chevy V8s/carbureted. However, with a friend at helm and motor ON, wiggle temperature sensor wires and see if there is any temperature gauge change. Time to pull risers and test them, if salt water used. With a friend at helm switch, you should be able to disconnect hose going into riser from pickup for a short time and see if water is coming from OD to motor via impeller (if Alpha drive). If Bravo, with a friend at helm switch, you may test in a similar manner for water restriction in transom assembly (Bravo-itus) that will require installing a kit. Pull hose from transom assemble going to PS heat exchanger and check for water flow. Are you sure that you installed thermostat correctly?

Yes on the thermostat. I used an OEM to make sure it was the factory temp.
Once the thermostat opens it drops to normal operating temp and I have no more problems throughout the day.

 

[7Ralph]

Yes on the thermostat. I used an OEM to make sure it was the factory temp.
Once the thermostat opens it drops to normal operating temp and I have no more problems throughout the day.

Also used on an inland lake exclusively.