Just throwing this out there, you have checked, flushed, and replaced all kinds of stuff and pressure is still to high. Swapped sensors and problem stays. Do you think it might be the gauge that is in error?

With out the direct water intake pressure is LOW, not high. I assume it's high with the transom pick up due to water is forced into it harder then with the outdrive intake. I have vessel view, the read outs are right. Temp does creeps up a bit to 160-165 may be 170 but I don't run it long enough, just short test runs. There is GOT to be an air leak and sucking air, but there is only a few places this can happen. I wanna cry.
:(

HyFive578, what kind of water pressure are you seeing on your 525's?

Man, I know what you're going through. I've been chasing same problem for 2 years - as I mentioned earlier, Eddie did some things to my drive to help, and hopefully later this month I'll be able to confirm his work.

One of the things that I continued to question myself was an air leak at the barbed fitting on the transom. Both of my engines have 2 hose clamps there, and while difficult to get to, I believe that mine are tight - but that hose is very sturdy, so I was never confident that they were actually providing a air-leak free seal.

Have you reconfirmed those clamps?

Other than the engine differences, your troubleshooting path sounds exactly like mine - and I never got to the bottom of it. Eddie said my blocks were full of river crud, so maybe that was it (sea water cooled engine). But when pulling the block drains, water drained freely.

I know you've had sea pumps off/on/replaced, but are you certain that they are mounted squarely to the mounting base and not sucking air?

Easy... I swapped the drives lines once already. Sucking from port drive to strbd, problem remained. Port pressure was good. meaning; lines, hoses, clamps etc is ok. IF there would be a problem then port would have low readings. Closed cooling, there are only a few hoses etc, that could have any problems. Hoses are good. I doubt there is a restriction, otherwise I would read "high' WP. I think the volume is less then it should be, sucking air. No clue where. Impeller and housing is ok. I might put some soap/water in the lines, plug them somewhere and air pressure. Watch for bubbles.

Any chance of the belt slipping, tensioner issue while pulling through the drive?

That could cause the issue. Not sure how to check, but belt is tight, pulley and everything seems ok, no "slipping" noise at all. No wear or rubbing on the belt or pulley.

Just a thought as with the external pick up its being pushed through the pump, maybe try swapping belts.

It's a good thought. I can do the belt swap, easy enough. The only tube that I could have any air leak is the hose from the drive transom fitting to the pump. All the other hoses are in positive pressure. No water in the bilge. Swapping the drives might moved the hose to a position that a pin hole might be closed, and that's why the pressure was good on port. But why strb. remained low? I will remove that hose if I can and replace JIC.

No, I was referring to the bypass pushing water much harder, therefore the pump and pulley aren't working as hard.

At idle, I see anywhere from 4-7 psi. Cruising at 3500, I see high 20's. with RPM's from 4000-5000, I see mid to high 30's. And my engine temps rarely exceed 160, almost always around 155.

I'm just spit balling so sorry if its an issue. But high/low readings my point is it could be the reading (gauge). You have vessel view but the readings are interpreted by the computer based on readings coming from the sensors. The wiring or computer for the readings being seen are not without error. Not saying this is your issue but just a WAG. To find out if its the reading on vessel view, just wire your port sender to the starboard and vise versa. Let the reading from one motor show up on the other reading.

Dodge bud.. No issue with any comments. I welcome all of them, and appreciate them. I might have to check the reading, but since my temp. does creep up a bit, I think I am getting low WP and low volume somehow. Using the direct water pick ups, while my WP seems a bit high, temp is good. Forcing additional water into the system works.

Is your water pressure measured with a water line to the dash or is it electric? If it is electric my suggestion is to measure the water pressure with a mechanical gauge at the the intake manifold. If you don't have one, I can lend you one.

The real puzzle here is that the temp Guage is verifying the pressure readings, so we all have to think outside and around the box, possibly within the box ! Did I mention I love puzzles! Paradox , we will figure this out.

I hate puzzles LIKE THIS. But my screen name sure fits many of my situations in life. :)

Next step. Installing a clear plastic tube, right before the pump housing. Outdrive in a big tub and see if there is any bubbles = sucking air from the intake hose.

11 AM update, Changed most of the clamps, plastic tube is in, no bubbles. (well, very few small bubbles, which might be ok, picking them up from the tub while hose is running) 4-6 PSI at idle, 10-12 at 1500 RPM's. Not running any higher on shore, but will do a test trial again in the water. will see?.

Is this the engine with or without the power steering and cooler, and where is the sender located in the maze? I looked at the 525s in the classifieds and your right with that serpentine setup I don't see it slipping.

Power steering. Power steering pumps and coolers is on BOTH engines. Neither motors are "primary". I get power steering with either motor on, and of course with both on. Normally when I put - put, I use one motor, and alternate. THis way I can keep the hours lower. I removed the hose from the PS cooler as well and while I can see in it, I can blow air through it easily.Besides, the PS cooler is after the water pressure sensor. THe sensor is on the top of the oil cooler on the starboard side. After hose item No. 5, right above No. 2 on top of the cooler. Anything past that point should show High pressure if there is a blockage or restriction. So I would think.. See pic.

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I'm running out of ideas, but when you reinstalled the sea water pump housing, did you coat the mating surfaces with Perfect Seal? Just to eliminate any air leakage there??

Another thought I had, was the bearings inside the water pump / fuel pump assembly. If they are worn / slipping, maybe they are not holding the impeller under pressure. The fact that you're getting pressure from the exterior pickup is from the force of the water being pushed up there, so I think that is purely coincidental and my suspicion is that if you go that route, you are not solving the problem and something else will fail or alternatively you solve the problem and then you will have way too high pressure.

It will be a pain in the butt but a possible way to prove / disprove this theory is to switch the entire sea pump / fuel pump assemblies on the two engines and see if the problem moves. The temperature creeping up confirms there is a flow / pressure problem and that its not likely the sensors.

Hy 5. That bearing theory sounds interesting. It is possible, but not sure how to check with out swapping the whole thing. I might have to do this. It would explain why the low WP stays with starboard. There is no noise from the pulley and fuel seems good. I will do a test run again and if no luck I will swap the assembly.

Hiy5 you beat me to it, swapping pumps or at least moving one to the other engine will tell you if it is a pump issue. The only place in the diagram I see to allow any real pressure are the headers or the hoses that feed them.

I don't think you would hear anything coming from the pulley and unless you know for sure what your fuel pressure was beforehand and then now, you might not be able to detect only minor slippage since the pump is still pulling water albeit lower pressure. I'd try swapping the pumps, it's not that much more work than changing two impellers and could solve the mystery. If not, I'm not sure I've got much left but I'm working on it. LOL.

Come to think of it, checking fuel pressure might be another indicator, but emphasis on "might", I'd do the pump swap. If the problem moves, then you know for sure it's the pump.

OK.. Before I start wrenching, I will do a test run again first. However, even if the bearing is shot? isn't the pump shaft one peace? and the small pooley adaptor is pressed on or have a key? then the large pooley bolts on. So how could it spin less with a direct one peace shaft with a key for the impeller? Symptoms do indicate that the impeller is spinning slower, just don't see how could it. Just courios, but I will check around if I can borrow pump housing so I don't have to do this in and out thing 4 times. lol

That would cause misalignment in the housing, and reduced efficiency.

You want the whole pump assembly, not just the housing. You should also check / replace the gear lube in the pump too while you're at it (but after the experiment). These pumps are notorious for leaking fuel into the gear oil.

lol.. I know what you meant about the pump housing, (with the fuel pump attached). I have 1/2 doz. plastic impeller housing around. I change them once or twice a year, JIC. I talked to Merc. They don't think it's the pump itself. The shaft is keyed so the impeller can't turn any different RPM then the pooley, but agreed that it can be the last thing to do, so I'm doing it. I hope that's it. I will replace the hose from the transom to the pump first. There may be something I can't see under the motor. A hole or ? But I'm stumped since swapping outdrive intake the LWP remains with starboard. Can't be the hose, can it? lol and GGRRrrr. Mystery of the century here.

:popcorn:

I really hope you solve it. And very curious to know what it was...

On the lighter side. Several years ago I had some heating, water pressure issues. Nothing major but one hellava dilemma. Turned out to be a lizard skeleton in the oil cooler. :) go figure. I been taping and covering the outdrive water pick ups ever since during storage. I'm ready to see some wasp nests somewhere. :)

That was going to be my next suggestion, swap one hose and one cooler at a time look for a change.
a question for those in the know, if the dumps into the headers were eroded or cracked I can see that resuting in lower pressure, but the flow would be there so I don't think that would elevate engine temps but I don't know.

WWoooo Hoooo. :) Pressure is back where it should be. Temp is good, like it was. Life is good for now. lol. After a few Heinekens, I will post what was the problem. (with pics) BTW a $10 item. What an ordeal, but I have a boat again.

I offer this so NO ONE has to go through this BS. I been using "T" clamps for years. IT is a better clamp then the standard or even HD hose clamps. SO I screwed up in reverse. I do check the tightness of the clamps regularly, but I forgot about the rubber hoses having a "memory". See old hose with the typical clamp markings. After some time the hose actually retain it's compressed state. No biggie, you tighten the clamps and off you go.
Unless your clamp is tight already, as mine was at the impeller housing, BUT While it was tight and could not really be tighter, the hose actually retained a smaller diameter so while the clamp was tight the hose did not "compress" any further. See Pic "A" there is no more tightening possible on the clamp. It's fully "closed". Pic "B" shows more room or space to have compression. Both are about 1 1/2 " to 1 3/4" in the picture. (for typ Heavy wall tubing) Clamp "A" , I could not compress anymore, it reached it's limit. So while I thought the clamp was tight, the actual seal was apparently not tight enough. It was sucking in air at higher RPM's. Once I replaced it with a "smaller" clamp, due to the hose with age is actually smaller OD. The problem was solved and all is good. Smile at my mishap, but remember it. :)
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Good to know and thanks for posting. I always try and twist a hose after tightening to make sure but don't know if that would have helped. :ernaehrung004:

Fantastic!! Glad it was simple.

I'm glad you found your issue!!

lol.. Right... 6+ Mo. of headaches.

Sorry to grab out this old story!! But it was very intersting for me,as i have same probs at moment!
I do some work at engine,600sci,in winter like headers away and so.
Now add an Sportmaster lower to the XR Upper and lost waterpressure.it will not go over 20Psi.Last year was allways over 30 with DWP Lower.
Like you, i have checked all stuff like waterpump,fuelcooler and so on.
Test the Pressuresender smartcraft today with air and my system shows the pressure i give to sender.So this work good and real loose pressure.
I have an T part in the line to waterpump for flush the engine.Will check tomorrow all clamps there as i nevver belive that a small leak there can make so much trouble with pressure.
will see!!
I will not belive that a Sportmaster with LWP will bring down Waterpressure.Normally pressure go up with this or not?
Thanks for your search story!
Michael