I am working on a 1999 502mpi with a bravo 1. How much water pressure should the impeller generate? I checked the rubber propeller. But it looked good.
The engine over heats after 10 minutes of idle, so I removed the hose going from the thermostat housing to the right exhaust and there wasn't much pressure. It kinda came in spirts.
I took it off before the thermostat and had the same thing.

Water pressure at idle is only 1-3#. Mine barely moves the gauge.

Ok, I don't have a gauge.
Shouldn't the 1" hose have a steady flow of water through it?

Your steady flow of water should be at the output side of the raw water pump. Bottom front of the engine on the port side.

Are you running it on a garden hose or in the lake? My temp comes up over 180+ if I let it idle on the garden hose, same with a friend of mines, but they both run cool as can be in the lake. Maybe not enough supply of water I guess?

Thanks, I know the pattern in which water flows I just don't know why it isn't flowing enough. I didn't notice a problem when hooked to the garden hose. The temp gauge slowly climbs when on the lake. My temp alarm goes off at 210 range, after 15 min at idle.

I'd back flush from the Thermostat housing up to the sea pump ....install new impellar ..check the housing while you got it apart for deep grooves ...if that doesnt work remove the thermostat ...or remove the thermostsat first ....m

ok, so lastnight I tried to back flush the hole system.
When I took the hose exiting the impeller pump off and started the engine, there wasn't much water coming out. I would guess it was less than a gallon a minute. And, the water was coming out in spirts. Kinda like waves. A goosh would come, then nothing, then some more, then nothing.
I just check the impeller and greesed it. Everything looked good.
Last night I back flushed the hose going to the outdrive and it all looked good.
Ideas?

Even though it looks good, are the rubber ears on the impeller fatigued? For all that they cost, I'd put a new impeller in and see what the difference is.

You should not grease an impeller. Use dish soap when installing it.

You need to start at one point and start back flushing. Start where the water comes thru the drive at the inside transom assembly.