Bubbling/Boiling in my Engine Raw Water Strainer

[rmbrown]

So, when I bought my boat, my thru hulls and seacocks were of questionable quality and in need of replacement... so I did.

While I was there, I replaced my raw water strainer for my engine.  It's capable of a much larger flow than the original and I increased the diameter of the hose to the engine from the strainer while I was there.

It's installed so that if you take the lid off with the valve open, it will overfill the strainer bowl.  My normal operating procedure is to close the valve, remove the lid, clean the strainer, open the valve until the bowl overflows, close the valve and put the lid back on, then open the valve for use.  The lid is domed, and the exit to the engine is through the side of the bowl.  I'd prefer to get all the air out but I've not yet come up with a way to do that.

All that said, it seems to work like a champ but I was down below looking at it while running the engine last weekend ans was surprised to see the water "boiling".  Not from temp, mind you... and not, to the best of my knowledge from any air that might be traveling that way from the engine should the system not be functioning properly, but just because of the movement of the water... I suppose.

I feel like I'm missing something and that this is an issue.

[rmbrown]

The coolant that you can see around the rim of that lid is coolant that dripped out of the reservoir immediately above it that runs down and gets under that lip outside the o-ring.  A problem, but unrelated. :)

[Stu Jackson]

Mike, My f-i-l's pool circulation pump has a big strainer placed right in front of it.  Does the same thing.  Been that way for the past 22 years.  Freaked me out when I first saw it.   Could be just 'cuz it's big and has a lot of volume in the body.  As long as all it is passing is water and not any air and there's no sign of engine temperature creep.  I was an engineer, used to be able to explain why, but I retired, so all I got for ya these days is: "If it aint' broken..."

[rmbrown]

I talked to Randy at Forespar and he told me that this was normal.  He said he'd send me a scoop that I could add to decrease the chances that at faster speeds I was getting some air bubbles sucked up from the through hull along with the water.

I'm not sure how big it is or how it attaches but may give it a shot.

Stu... re not passing the air and just passing the water, I'm right there with you.  The air doesn't go away and I don't think that the cap could possibly be leaking given the how it seems to fit so I don't think it's sucking in any new air, but that's my only measure of whether it's passing water only.

I'm seeing 165 at 2000 RPM but 185, give or take, at 2500, so I'm still looking for the culprit.