Block pressure water sender

[Christian]

Hi all, My boat is SeaRay 37 - 2006
I have different measurements of engine water pressure. The port always marks me about half. I have already changed both sensors and put them original Mercury. The sensors were located above the transmission oil cooler. Does anyone have any idea about this difference? Please refer to pic below. 3.5 vs. 6.5 @ 1000 rpm

 

[Bt Doctur]

I`d be more concerned about the scheduled service for the impellers and not the water pressure.
How about the 3.5 meaning a full flowing system and the 6.5 meaning clogged manifolds or elbows?

 

[Christian]

Well.. it makes sense.. How can I check manifolds? Whats the normal water pressure in this kind of engines? (8.1S horizon)

 

[Bt Doctur]

Somewhere between 2011 and 2012 the manifolds should have been changed if they are not using A/F
and the elbow also.If manifolds are FW cooled then just the elbow should have been changed
So using that timeline the current manifolds and elbow are coming up on 8 years.
The sign of a failing manifold if raw water cooled is a hard crank or a miss that goes away, same thing with a elbow thats leaking. Checking the sparkplugs for a blistered pure white is another indicator of water ingestion.
So if your sure all those are still good that start at the :
inlet screens, inlet filter screens, seacocks , trans/oil coolers, raw water impellers and pump bodies, and finally where the water exits, the elbows.
You would be amazed what gets into those things.

 

[Seapig]

3.5 @ 1000 is low. I’d be suspicious about some pump housing wear that’s reducing output. Mine run around 3 PSI at idle and if I recall correctly, low teens at cruising speed.