High water pressure and oil on gear housing - 1984 Mercury V150

Rebuilt my powerhead a couple years back and it has always had a fluctuating water pressure at idle and at first part of throttle, then goes steady after about 1500 RPM. I have had no issues with engine until just last week when I put in a new water pump impeller. I now have 13 psi at idle and still the fluctuating water pressure at around 1500 RPM (engine is running in barrel). At 5000 RPM (out on the water) I am up over 25 PSI. I found a hole in my poppet diaphragm, so replaced it, thinking I had found my high water pressure problem. Put engine back in barrel and ran again before taking to lake. Still had fluctuating water pressure and 13 PSI at idle....but also had a lot of dirty oil on top of the water in my barrel and when I pulled engine from water there was dirty oil on both sides of the gear (prop) housing. The oil felt like it had fine sand in it.... maybe carbon deposit form exhaust??? Any thoughts on what is wrong?

Oil scum normal for running in barrel...sound like the poppet is sticking or binding at low pressure and 17psi+ is OK for high side

Likely the pump is picking up too much exhaust from the barrel.-------Sounds normal with all the oil in a barrel too.-----What is idle water pressure with boat launched at the ramp.

Idle pressure was 13 psi. I Read another post that said idle should be 3-7 psi and at 5000 RPM should be 17-22psi. I have not read that in any manual yet. I do not recall ever having more than 6-8 at idle....or more than 20 psi at 5000 RPM ...which is why I wonder how I am now at 25 psi with new pump impeller. I hate to see a new power head go poof! So I am a little cautious...which brought me here to ask some more experienced users. I appreciate all the help and input.

Back up a lil.....is the replacement powerhead a 2L???? Does it have one piece or 2 piece heads?

faztbullet said:

Back up a lil.....is the replacement powerhead a 2L???? Does it have one piece or 2 piece heads?

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It is the original 1984 powerhead, but rebuilt. So 2L and it has the cylinder head and head cover (I am assuming that is a 2 pc head).