Bravo-merc 525 water pressure issue
 

400ss I have bravo 3s. One lower has lower water pick up the other does not. The one with out lower water pick up reads between 5-6psi at idle. The one with lower water pick up is 10-11. New transom assembly’s 4 years ago and haven’t seen salt water ever. Never had this issue till this year when I just dropped it in. Back flushed. Retighten all hose clamps related to sea water system. Pull inlet hose off pump from (goes from transom to pump) to check water flow. One with low water pick up def flows a lot more then one with out lower water pick. Both engines running at idle the one with low water pick the collectors are ice cold. The one with out low water pick up the collectors get warm. To me seems like a issue between drive/transom/and pump. I did have the drive serviced over the winter. Also brand new water pump and fuel pump assm. Is it possible a seal between the lower or upper and transom assm is dislocated or am I shooting a pipe dream. Any help would be appreciated. Thanks

So are you saying they both use to be 10-11 lbs @ idle ?

yes! Both collectors were always cold at idle too

new water pump ? circulation pump or sea pump

new sea water pump. Just put a complete assm on it that was rebuilt. I changed the water pump on the old assm thinking that was the issue. Wasn’t. So just put a whole spare assm on and that didn’t change it

10-11psi of water pressure at idle is a ton. Mine at idle is about 2 psi. More important is what is the water psi while running?

I agree your water pressure at idle is very high. By backflushing you did the power steering cooler, oil cooler, the heat exchanger and the fuel cooler all individually? The fuel cooler is directly aft of the impeller housing, many people don't realize it's down there and address the other coolers.

the water pressure has been like this since day one of owning the boat (5years). I back flushed every cooler and hose and tightened all hose clamps. With the inlet hose off the water pump. (Hose from transom assm to water pump). The one side is less water flow in with boat just sitting in the water. At cruise that engine is 3-4 psi less. At full throttle I have 47psi on the port and 29psi on the starboard. The starboard one is the one I’m having an issue with.

Sometimes you can back, flush tighten all you want. No change. I has similar issue few years back. WP at higher RPM's wasn't bad just a little off, and volume was a bit less.
Turned out to be lizard skeleton pieces stuck in the oil cooler holes. I had a SST flat little rod pushing it through all the holes everywhere, problem went away and I found a few little bone looking things. I used an old windshield wiper blades metal fillings, Nice and strong, but flexible and rounded corner. Now I always have one in the boat. :)

Can’t get videos to upload to show the difference of water flow from inlet hose off transom assm

thats crazy high........even the 29 seems high to me

I get 3-4 psi at idle on my 525. Service manual says max pressure at speed is 43 but I regularly see higher than that and so do many others so 47 is fine. The 29 psi I'd be concerned about, as you are!

Edit: F-2 Speedy, I respect your knowledge but lots of us run that high of pressure on a 525.

Bravoitis on the stbd side ?

To post a video, you have to upload it to youtube and post the link.

My vote is you have a partial obstruction somewhere.
With closed cooling like the 525EFI, I think 40psi at WOT is fairly normal.

Well I stand corrected, cuz I don't run antifreeze motor's......:lolhit:

Ya, this still baffles me, how a single bravo pump can move that much water at idle, I guess drill 8 holes in the other lower and call it a day............:D

4 year old fresh water transom assm

1st thing always is to put something thru each water opening in the oil cooler.....as previously told. Doesn’t take much for a few or. 10 or 20 tubes to get something in them.

Many times back-flushing does squat.

Soeaking of which always amazes me how many big chunks of impeller I find in entrance of oil cooler in a boat with an impeller that’s in good shape. Person changing the blown apart impeller dumb or lazy or couldn’t give **** ? Doesn't’ wonder ‘Hey, wonder where the pieces went ?’

I guess I’ll go through all coolers again. But this all started as soon as I put the boat back in the water this year. Only thing that has changed is I had the drive gone through. The motors keep same temp at 150. Only difference I can physically tell is the top of the header collector gets warm and other stays ice cold. I tried loading videos to you tube to post but it’s not working if someone could help that would maybe help Thanks

Okay, well...,
Maybe recheck the drive to transom water transfer oring and if okay check lower drive to upper water transfer oring. Maybe f’d up or ??? during service/installation.

47 is approaching the upper limits, the 29 is not high on closed cooled 525/600/700

Remember on 525/600/700 its about water flow not water psi to cool the headers, etc. If your headers are getting hot thats definitely not a good scenario for header longevity, your water flow is compromised. Start from the beginning trace the lines taking each line and each cooler apart. Make a tool that your comfortable with to work thru every single cooler opening most importantly in the opposite direction of flow. Back flush each in opposite direction of flow. Take your time you will get it. Finally while at it, make sure your impeller and impeller housing are brand new and not defective for a successful season. Debris in one of the coolers could have dried out and hardened over lay up period causing the blockage.

They are not getting hot (yet). That’s what I’m trying to avoid. Believe I don’t need and want to spend $5k for headers. But I will go through the coolers. Report back what I find. Thanks