Pressure testing ex manifolds
 

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

Re: Pressure testing ex manifolds
 

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.

Re: Pressure testing ex manifolds
 

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?

Re: Pressure testing ex manifolds
 

US1,
this is from merc manual

Re: Pressure testing ex manifolds
 

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.

Re: Pressure testing ex manifolds
 

Thanks guys.

Re: Pressure testing ex manifolds
 

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

Re: Pressure testing ex manifolds
 

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.

Re: Pressure testing ex manifolds
 

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 :cool:

Re: Pressure testing ex manifolds
 

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....

Re: Pressure testing ex manifolds
 

No, I have SS risers and these manifolds and risers were new in the spring.

I truly think the moisture I'm getting in that one is due to a slight restriction after the water outlet from the riser, flowing into the Corsa. I'm going up now to pressure test with a water hose, then pull that boot and cut the rubber "ridge" out of the boot so the water can flow straight out into the Corsa without anything in the way causing a disruption in flow. I'm wondering if it's at idle, on the muffs, that's it's reverting slightly because of the water bouncing around at that joint.

Re: Pressure testing ex manifolds
 

SR Jim,

Is this what your risors look like?(the SS ones) If possible, would you mind getting a couple measurements for me if you have access to the outlet end of the risors? Having trouble getting them elsewhere.

I need the ID dim. of the outlet nozzle and also the length of the nozzle that extends past the water outlet holes at the ends. Mine (black alum.) do not have this nozzle and I need to add them on.

Thanks

Re: Pressure testing ex manifolds
 

If you can rig it properly the best test you can do by yourself would be a helium test underwater. Helium has a smaller molecular/atomic size then water or air...(its the second smallest atom). The helium leak rates will be more than, say, water or even air. However, helium leak detection requires a very sensitive "sniffer" whereas water is pretty easy to detect. Thus putting the item undwerwater would help detect the gas without the "sniffer"

But for our purposes i would just get an air line and put a regulated 40 or so psi in the manifold and let it sit underwtare over night and see if you have any leakes in the morning...maybe even do a overnight leak down test if you have the tools for it. Oh and i think i would put it in hot water......you want to try and simulate the metal being at working temps as much as possible to see if any cracks that me be closed when cold open up as the manifold expands! :)

Re: Pressure testing ex manifolds
 

By the time you posted this I had already been to the boat and back! But ye, the SS on the left are what mine look like, although mine are taller.

I'll try to give you ballpark #'s, best I can. I do have the riser off, and I pulled the boot off so I could see how the riser was sliding into it and how much restriction my boot is causing the water flow out of the riser.

The riser is about 4" overall OD. I'd say the water outlet is about 1/4" to 3/8" so the "inner pipe" or nozzle as you call it, is going to be about 3 1/4" to 3 1/2". It's probably a 1/8" walled pipe so you can do the math for the ID.

I'm not sure when I'll be back at the boat, or if it will even be this week. If it is, I'll get exact measurments.

I did pressure test and was able to get pretty good pressure (from a hose) on it. Everything seems fine. Even the ridge inside the boot is actually not blocking the water outlet ports like it appeared to be, but they still could be causing a disruption in water flow, splashing it around. Who knows. I'm going to replace that just to make sure. Since the risers are such a breeze to pull off, I can keep an eye on it. At least it appears no water is getting in there from the manifold or riser.

Re: Pressure testing ex manifolds
 

We test manifolds at 60 PSI for 10-15 minutes. The water jacket is pressurized and the header tubes are filled with water. If no signs of air bubbles occur, you are in good shape.

Dean Gellner

Re: Pressure testing ex manifolds
 

I plugged 3 of holes and air to remaining hole at 60psi. Placed manifold in a bucket of water. Got some bubbles out of 2 of the manifolds where the outer case is welded to the exhaust flanges. No air bubbles from the inside.
Going back to the welder, then retest.

502 HEAD COOLING WATER SEEPAGE FROM HIGH WATER PRESSURE. Replying to MOP's old post about the PRV's on cooling water pressure.

These PRV's from Mercury Racing are an engine saver. Expensive but worth every penny.
After reading for a long time on OSO on a lot of articles about 502 head leaks there was one knowledgeble gentlemen that had been around for awhile and said if you are running more than about 20 or 25psi that you would most likely see corrosion/leakage on the outboard side of the heads. Sure enough, i had both heads both motors with corrosion at the gasket and rust on the block below the gasket line.

Bought these PRV's from Mercury and ALL of the seepage stopped completely. Thanks for this one gentlemen's comments. Wish i could remember i would thank him. These PRV's have never stopped up or failed to hold exact pressure.


I actually went out and found a lighter spring that fit, and ground the OD a little bit more to reduce the set pressure on the factory Merc PRV from 30psi to 15psi. The blockpressure runs higher though. - was actually about 5psi higher i presume from the circulating pump at higher rpm.

Ended up with about 20psi in the block which is where i wanted. It.

I guess with much bigger power, you might need a small amount higher pressure to prevent hot spots, but I have never had any issues at 20psi, and no more corrosion/seeping heads.