so I have been trying to track down why I have low pressure in one motor . I replaced both sea pumps. Then again on the low pressure side. I used my boat once the year before but never ran it up to temp. Was very busy. So this year I have gotten out on it 3 times and trying to find the problem. The last year I had water in drive bottle in that side. So pulled the drive Nd had new seals put in. Do you think if the o ring in the drive was pinched it could pull enough air to make my water pressure fall on its face. I opened sea strainers and made sure it was clear and checked all hoses on the intake side . I just put the drive ( cavitation plate ) deep in a barrel and tried it. Same effect. Just wondering if that o ring could be the factor

I do have it running hotter. To be clear I have 9psi in one motor and 4psi in the other at 3500 . I can’t run over 50mps for a long time without water and oil temp creeping up . Other motor is fine. I believe it has to be on the suction side. Be then again I pressure sender is in the intake manifold . But I did see while in the barrel Today when I brought it up to 2500 rpm the gauge fell on its face and me sea strainer empties. I changed the hose that runs through the transom On the other side thinking it was that when it was just a tstat. When I did it it wasn’t crusty at all. It was a fresh water boat. I think it may be the O ring in the drive.

merc hp500

How old are the transom assemblies and are they used in salt water?

It was a fresh water boat. I did change the hose in the transom in the port side thinking it was a problem with a temp condition but it was tstat. When I changed it it was clean.

Lwp and never had a impeller come apart on me. I have good flow from flush to through the drive also