Idk, hoses? You are thinking they are colapsing.

These problems and water intrusion have to be the hardest to solve on the marine world.

Just for giggles, have you checked your serp belt tension? What about the bearings on the sea pump?

I doubt I would be able to see the hose collapsing. The hose is very stiff - possibly with wire. So my guess is the inside may have separated from outer and is collapsing. As you can see in this picture, the hose looks to have failed, at least on the end.
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Looking inside, I cant really see any delamination or defect. I spoke with previous owner, he said he never replaced these hoses (although he only had boat for 2 seasons). My guess is that the hoses are circa 2002.

I haven't measured belt tension, however my elbow is calibrated (I used to be an ASE Master Tech when I was in my 20's). The pulley spun freely when I put the new pump on about 1 month ago - and since the condition is the same today, as it was end of last year - my assumption is the pulley is ok today.

I appreciate all of the suggestions and questions - even the ones I've already answered. Helps keep me in check! :-)

I ordered an impeller for my seawater pump just the impeller. I received a no name impeller just a part # ( i was like this is going to be good ) the outside diameter of the impeller looked small but its the right part # and the rubber is very soft. I install impeller and that thing would not pump anything. Reinstalled old impeller worked fine. A worn pump housing will cause that also. Hope you find problem soon good luck and be safe!

Well, an update. Tonight, I removed and replaced (new) the transom hose. While I was there, I removed the transom water neck to confirm the thru water hose and fitting condition. Thank god, no "bravo fever" ! I didn't believe this was a problem on this boat, as it has a fresh water history. The bolts on the water neck weren't as tight as I expected them to be, but they weren't loose either. It was a MF'r to get the water neck off, however due to blowers and fuel injection setup. My arms were barel just long enough to reach the bolts to reinstall.

I also replaced the sea pump, just to confirm - although it was basically brand new.

We'll see tomorrow what happens.

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good thread. Hope you find your pressure loss soon.

Well?

No change. It doesn't seem to be as close to running hot - possibly due to the new sea pump, but still creeps up to and slightly past 150* during a cruise. It's got 120* thermostats so I'm thinking it should run around 130*.

But now, my port motor is acting up with same symptoms. My guess is the oil cooler is clogged again - I cleaned it out at end of last season. It would have been nice if Merc hadn't put the oil cooler where they did - it is such a PITA to remove and clean. With silent choice, there is no way to clean it mounting in place. So headers have to be removed at minimum. I've removed hoses and flushed with water, but generally those little river pebbles require a coat hanger to push them out.

#RiverLife !

Ran up to 85 mph in the poker run this weekend. Water temp was about 160* and oil temp was about 185*. Water pressure was up to about 10psi at that speed, so I brought it back down to about 60 mph. At 60 mph, water pressure was about 4psi, and water temp about 150*.

Am I just paranoid? Engines have AZSM kits with 120* thermostats.

Performance Report said....
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I have 120* stats in mine also and they run 155*-160* all the time. Oil temp runs about 150*-170*

That's good info to know. Appreciate the data point.