Boating

WATER PRESSURE

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Q:

I need to understand the cooling system in my 2007 200 hp E-Tec outboard.

I have the waterpress­ure sensor and its display on a multifunct­ion display via a NMEA backbone. In the past, the water pressure has been 4 to 6 psi at idle, increasing to a peak of 22 to 25 psi at 5,300 rpm. One month ago, I got an overheat alarm, shut down, and found the inlets blocked with weeds, etc. I cleared the blockage, restarted, and all seemed normal. On the next trip, the pressure remained 4 to 6 psi regardless of rpm. I confirmed water flow but cut the trip short. As a precaution, I had the dealer change the impeller.

Now the pressure still remains in the 4 to 6 range regardless of rpm for the first one to two hours of a run, then will go to the 20-plus psi range on the fast run home. But on the last run, it stayed in the 4 to 6 psi range regardless of rpm or time. Again, I have always verified the water outlet flow at idle and at speed.

What really controls the water pressure in the system? Are the thermostat­s stuck full open? Am I fighting a real problem or an indication/sensor problem? Once, after the overheat, the pressure stayed at zero after start-up; I immediatel­y verified water outlet flow, then shut down. On restart, I got the normal 4 to 6 idle pressure. Now I have the strange indication­s described above.

This has been a great motor for my tri-toon, and I do not want to kill it.

Mike Moran Rhinelande­r, Wisconsin

A:

Hi Mike. Boating’s colleague Glyn Austin, an E-Tec guru, provided this answer:

“Water pressure is controlled by the impeller creating the pressure, thermostat­s opening at a certain temp, and the water-pressure bypass valve. The valve has normally opened from approximat­ely 4,000 rpm and higher. If that valve is stuck open, then you won’t see much pressure, but you should never overheat, as there is maximum flow through the engine.

“However, along with pressure, I always watch my temperatur­e. From my experience, my 200 E-Tec ran around 170 degrees, and when the water-pressure valve opened, pressure would drop, and my temp would drop approximat­ely 20 degrees to around 150.

“My thoughts would be to check the thermostat­s and the water-bypass valve for blockage and make sure water can flow through those components, and then I would look at the pressure sensor to see if it was faulty. I would also look at the water tube and make sure it’s sealed at the water pump so water is getting to the powerhead as necessary.”

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