525sc no water pressure
 

Hello, all.I've been chasing this for awhile, So I have Good water flow but no pressure, After about 10 minutes on plane, the overheat alarm goes off.My coolant temp is right at 140ish Oil temp is right at 180, I physically cleaned out the oil cooler , New sea pump. Not sure what i'm missing, But ever since I have no water pressure anymore.I've been getting this alarm,

It wouldn't be the overheat alarm sounding if your coolant temp is only 140... Perhaps you are getting a code for low water pressure? The stock merc sensors can trigger an alarm if they get sand or crap in them and read incorrectly.

It's a carb motor I don't think it has all that computer stuff, The water gauge is mechanical, so no sensor on that,

do you have a power steering cooler?if its before the oil cooler,back flush that.
where do you get you water from,,drive or transom mounted pick up?

Power steering cooler is after the oil cooler, I do have a drive pick up, gimble housing was replaced last year. Fresh waster only, engine block was also replaced last year,

Also forgot to mention, If I take the thermostat completely out, I still saw no water pressure but my alarm doesn't come on anymore, And the water temperature fluctuates pretty good from 100 to 190

are you sure you put the thermostat in the housing the right way,,you have to look at the diagram to see where the thermostat goes.
did the problem show up after the gimble housing?

Do you mean that you have ZERO psi of water pressure???
That is nearly impossible if you have some flow. My 525SC had around 1-3psi at idle and 20psi at WOT
First thing to do it verify that the gauge is working and the hose to it is not clogged. Where is the hose connected?? If its at a block drain, its probably clogged in the first few inches or it has a kink somewhere

I did an impeller on a 700 SC last year. It had dry exhaust, and at idle, after the new impeller, the water pressure gauge was zero, but still had a solid stream coming out the back. I immediately shut down and called the owner, he confirmed the gauge was always at zero at idle.

Can you refer me to a diagrams do I can double check

Yeah, I'll double check.I'll probably just get a new Gage and double check, How would I go about clearing out that line if it is blocked,

a thin piece of wire

Zip tie in a drill works wonders as well.

What else could cause my high temp alarm to go off, When the gauge reads normal

Perhaps the temp switch is faulty or the gauge is reading incorrect? Have you had a chance to verify the actual engine temp with an IR temp gun?

not yet. Headers were really cold to the touch as well, if that means anything. Almost like it feels all the water is going to the headers and not through the block

Oil pressure switch, water temp switch and drive reservoir are all spliced together on the 525SC.

Id bet you have no water issues, but a switch issue. If I recall correctly that is a 190* switch, next time shoot the thermostat housing with a IR temp gun and verify your 140* water temp. If your gauge is accurate, then replace the over temp warning switch.

again,the thermostat housing needs to be looked at.
easy way too,take it apart and switch positions of the brass collar and thermostat.

So right now the brass collar is down on the bottom, my thermostat sits on top, I'll swap em as well.

yup,swap the position.thermostat thats your problem.

Diagram
Thermostat Housing (mercruiserparts.com)

Thank you all for the input, Won't be able to employ it until may, it's my next ti.e I'll see meh boat