My stbd 525 efi does not have any water pressure. Ive replaced the impeller 3 times already this year, th elat time being, the last itme i took the boat out. When a hose is hooked up to flush the engine, pressure is fine. when i dropped the boat in the water and fired it up water came out the exhaust, but no pressure. water soon stopped comeing out (went through what was left in the hose) I have not had to replace my portimpeller once over the past year. My headers are also burnt on my stbd side. What coudl be causeing this? the sea strainer is clean. what is the best way to diagnose my problem?
thanks
-Rick

Have you check the fresh water flush hose for a leak or for being tight.Happen to me once the plugs wasn't tight so it was sucking air.

Check the front shaft of the raw water pump , I have seen them suck air from the seal there. If there is any play in the shaft this is very possible. Bearings and the seal could be worn. I have seen this quite a few times. Tom

Make sure you have reinforced hose from the out-drive to the sea strainer and on to the raw water pump. It could be collapsing under suction or there could be a blockage in the pickup.

Also make sure pulley is tight on the raw water pump

check two things, check where the water intake hose come thru the transom on the inside,remove the hose nipple and make sure the hose is not resticted from corrosion, and check the hose between the transom assy and the outer bell hosing make sure not cripped

back flush your system, you may have part of your old impeller stuck in the oil cooler???

how do i do that?

pull the hoses and stick the water hose in the opposite line to push the trash the other way. Been a while since I have done that. I'm sure there is someone on the board with more specifics on the matter.

here is a flow chart for your mtr will give you some insight as to what everyone is taliking about

thanks for all the advice, thats tomorrows project.