What's the recommended pressure for checking ex manifolds for leaks. SM manifolds.
Thanks

Wow, ironic you brought this up.

While North Texas style winterizing, I found quite a bit of moisture in one of my SM risers and manifolds. I dried it out best I could and left the riser off and next step is going to be to stick a hose on the inlet side (on the motor) and run water through whiole a hose on the outlet side (top) runs off into the bilge, and pinch it off to build a little pressure.

However, I think the rubber hose/boot may be disrupting the water outlet in the riser into the exhaust causing it to splash and revert at idle a little.

I hope to "pressure test" it early next week. Any other ideas would be more than welcome.

I had to cut off and weld on new lower fittings on the manifolds I bought, do to them being coroded thru in spots. Want to check the welds before off to the powdercoater. Do you have the aluminum risors?

US1,
this is from merc manual

I always take my Gils to 25 psi air, close the valve and see if it holds 25 for 24 hrs. If not, put it in the tub, submerged, to see where the leak is. Its usually in a fitting, but if not, youll find where its coming from.

Thanks guys.

Some will not agree but I feel the pressure checking should be done at a much higher pressures, at WOT the pressure can rise up to around 100psi. Especialy if you are running a transom pickup, Merc has a pressure relieve valve #863208A3 that will reduce it to 30psi. I am an old boat mech and when I was on the wrenches I would test at full compressor pressure which I had set at 125, I found many a leak in the upper range.

Phil

Does the exhaust see those high pressures? My motors peg the 35psi WP gauges at WOT. I'm hoping the bypass hose on the SM exhaust will lower that pressure a bit thinking that the small pass thru passages on the stock cast iron manifold to risor is a bottle neck. If pressure is still high, then my stat housing is the bottle neck.

I pressure test my KEs with city water pressure, I'm guessing to be 60psi or so. I block off the outlet port, hook up a garden hose to the inlet port and turn the water on. With the pipes resting in the position they will be on the engine, I then look for any water in the exhaust outlet ports (near heads). Any water is a fail.

BT

Guys, it's easier to water pressure test and it's much quicker. Make a block off plate out of aluminum with a hole drilled and tapped with a 1/4 in screw and torque it down with a new gasket (The bolt will act as an air bleed). Hook the manifold up to a hose and turn it on, then put the screw into the hole as the water starts coming out. Shine a flashlight inside the manifold and look for water seeping out or spaying out. sometimes it helps to put a little heat on the manifold/header because sometimes it wont leak unless its heated.

Samething goes for headers but instead of a block off plate, rig up a shut off valve to let the air out. Once there is no more air in the header close it off and check for water leaks.

The air thing is good but I think the water way is quicker and you don't need to spray soapy water all over the place to check for slow air leaks. Just my opinion, that's how I've been doing it for the last 10 years or so....