Offshoreonly.com - 2006 Chaparall 496 MAG twins. Low Coolant pressure

Offshoreonly.com (https://www.offshoreonly.com/forums/)

- General Q & A (https://www.offshoreonly.com/forums/general-q-20/)

- - 2006 Chaparall 496 MAG twins. Low Coolant pressure (https://www.offshoreonly.com/forums/general-q/353961-2006-chaparall-496-mag-twins-low-coolant-pressure.html)

2006 Chaparall 496 MAG twins. Low Coolant pressure

Hi All;

I have a startboard engine overheating. I have rebuilt the seawater pump and cleaned the heat exchanger twice. Backflushed the oil cooler twice. I do not think its a sea water flow issue as I see “Boost Presure” from the seawater pump numbers matching the Port engine. That is about 3 or 4 at idle going to 6 or 7 at RPM.

The strange issue is I see “coolant pressure” via smartcraft that reads 5 psi on Port and 2 PSI on starboard at idle.

At 2000 RPM Port goes to 16PSI and starboard only reaches 4 PSI.
This seems to be the closed system coolant pressure..

I swapped the coolant presure caps and that did not change anything. I check all of the hoses and see nothing loose or leaking. No indication of a coolant leak. I find it strange that coolant presure follows RPMs as much as the Port engine indicates. Is this is false indication of an issue or is their a coolant presure problem?

Thanks
Vince

That is the sea water pressure. How was the pump housing when you changed the impeller? If the housing ends are scored the water pressure will be low and you will have problems.

Is the water flow out of the exhaust the same on both engines? You can always switch water pressure sensors to rule them out.

Worn pump housing are a very common problem on the 496.

I had the seawater pumps Resurfaced to remove the scoring. So at this point I plan to swap the pumps port and starboard in the morning and see if the pressure issue follows the suspect pump. Thanks for your fast response.

By the way, If the coolant pressure is the high presure side of the freshwater system than what is the boost presure?

Thanks I am in Marathon in the keys and need to get back to Venice Fl this week.

Before you do that knuckle braking job of swapping the sea pumps swap the pressure sensors they go bad regularly