Water pressure high and oil temp high?!?!?!
 

I've got a 2000 502 Mag MPI that was recently rebuilt. It's supposed to be standard bore, standard compression with aluminum Procomp heads, extrude honed upper intake and computer flash from Arizona Speed and Marine. I had an issue after break-in period where oil pressure went low (alarm light came on). Water pressure was also a little low (5psi) and oil temp was getting a bit warm (230's). Motor was pulled and a high pressure high volume oil pump was installed along with a Hardin stainless steel seapump. Now...I'm seeing oil pressure around 45-50 psi at cruising speeds. However, at near wot the water pressure pegs (over 35 psi) and oil temp screams up to 230+ and oil pressure starts dropping...Mind you wot was only for about a minute! I've been told by Mercury that water pressure should be at 15-17.

Should I be concerned by any of this??? I've been told this shouldn't be a problem. I just have my concerns.

Yes you should be concerned with H2O pressure that high - you could blow a head or intake gasket and flood the motor with water, or worse yet, hydrolock it if a head gasket starts leaking into a cylinder. Any chance you could have a chunk of impeller or some other debris blocking the oil cooler? Where are you taking the water pressure reading?

Yea, sounds like you have a flow restriction somewhere in the system, after the sea water pump.

If I remember correctly, that boat has always read high water pressure - possibly gauge is 3-5 psi off?? But it would be wise to put another mech gauge on it to confirm.

Also, I believe you are picking up water pressure on the port side block drain. If that is the case, then I would suspect that high pressure is due to a restriction upstream - thermostat stuck, distribution housing corroded closed, restriction in header(s), or block has mud/sand/debris.

Have you checked the thermostat? Possibly stuck closed? Try and remove as a test - or put it in water and measure temperature as it opens.

Not sure about your oil pressure issues, as it's a new motor. I'm sure you're all over the engine builder on that one!

Good luck my friend. I'd be happy to take a look sometime if you need another set of eyes on it.
Terry

Thank you, Terry! I'm going to try and do some more troubleshooting this week I just wanted to get other opinions and try and figure out where to start?!

I was finally able to get in the boat today and do some looking around...the water pressure is being measured on the starboard side at the bottom of the block. I didn't replace the impeller nor the new Hardin sea pump. However, I wasn't having this high water until the new sea pump was installed (it was actually pretty low). Water temps have never been high (180ish all day long).