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Osco manifolds and risers

donald_r

New member
"Hello everyone,
I receive


"Hello everyone,
I received a tip from a Uniflite owner about this site and I can see right away how much I can learn from this group. Great topics of discussion!
I'm getting fairly stressed out with a couple of recently overhauled 318's in my 31'. All brand new manifolds,elbow's,risers and mounting kits yet on the first (starboard engine)start up I continuously am getting what appears to be fresh cooling water (about two tablespoons in each side) that is dark and contaminated with carbon. Upon shutdown I remove the bottom plug at the elbows and it drops out of the exhaust port into my hand. I was suspicious when on the second and third startups the tell tale rattle of a piston trying to compress water was evident. It would quickly spit it out and proceed to run like a charm thereafter, until I shut it down and pull the elbow plugs again and experience another couple of tablespoons of water in each elbow. I am suspicious that the o rings supplied with the new risers are not thick enough and some cooling water is getting over the orings into the exhaust ports. The boat is out of the water so cooling is via a garden hose to the raw water pump then via the heat exchangers to the front of the manifolds as well as to the elbows via the transmission cooler. Would anyone have any thoughts as to what might be going on here? I have had it suggested to me that there may be a set of brand new but faulty manifolds on my engine but I just cannot believe I would be so unlucky as to have two on the same engine, nahhhh! Could it be related to too much pressure on the system with the garden hose. Surely a sherwood or jabsco pump could provide the same levels of pressure at high RPM. Although I am stumped, I am also stubborn and will not let the culprit evade me much longer. Maybe with your help I can get to the bottom of this. Hope to hear back from some of you soon.

Thanks for your time
Don"
 
"I just remanifolded my 318 wi

"I just remanifolded my 318 with Osco's #826. I did not use any o-rings, just gaskets for the exhaust ports and manifold ends. Why o-rings? Seems like you would expect to have some colored water from a newly installed system. Let it sit, pull the plugs and see if you get water out of the plug holes. Otherwise I too am stumped, need more info. Good luck."
 
"David,
My risers are the s


"David,
My risers are the swivel type with inner and outer o rings. Could it be possible that the garden hose cooling method is providing more water than the muffler can comfortably expel thus backing up close to the top of the riser then spilling a bit into the exhaust port upon shutdown?"
 
"Oh, Don, I "feel your pai

"Oh, Don, I "feel your pain". Been there, done that, and I have the answer you need: epoxy!

1. Mark the swivel elbow's position so it will go back together in the same orientation.

2. Remove the O-rings and the stainless ring in the center and clean everything thoroughly

3. Make up some SLOW epoxy--do NOT use the 5 minute stuff (ah-hem!) Coat the O-rings, their seats, and the center ring with epoxy. (Pretend it's grease.)

4. Reassemble with your marks carefully lined up. Heavy snug all the bolts, but don't tighten them fully until the epoxy is cured. (Keep some left over epoxy handy as a guide.)

5. Tighten the bolts all the way down and go boating.

I can assure you, having done it this way several times, that you will never see another leak from that location.

Jeff"
 
"Jeff,
This solution that y


"Jeff,
This solution that you have proposed sounds very good! I do however, Have this critter on my shoulder that keeps telling me to check and see if the mufflers are not taking the water fast enough and it's backing up. I did raise them about two and a half inches during the reassembly process because there was not a gradual and even downhill to the stern ports as I thought there should be, but a sudden drop to the muffler from the riser and then a level flow to the stern port from the muffler. Now the downhill flow is constant throughout. Do you know about muffler inlets and outlets? I'm fearful that I may have reinstalled the mufflers out of their original orientation. How could I identify them, thus gain technical info on their installation orientation?

Thanks again
Don"
 
Running a marine engine direct

Running a marine engine directly on a hose has always been an iffything for me. What I do..
1) install a short ( 3 to 4 ft) length of hose on inlet of the raw water pump.
2) Put this hose into a 5 gal pail.
3) Put a running garden hose into the pail
4) start and run the engine when the pail gets 3/4 full.
5) monitor water level in the pail.
 
The height of the exhaust outl

The height of the exhaust outlet in the stern relative to the height of the risers is all that matters.

Trust me on what I wrote above. I did three of them that way and haven't had a leakage problem since.

Jeff
 
"Don - it's absolutely the

"Don - it's absolutely the case that marine mufflers (some of them at least), have specific flow directions. If, by chance, they were reversed, it could cause a back-up (and the junk that you’re draining could be carbon from the muffler…..backing up in the system upon shut-down). That said, it would be coincidental if you were to have reversed both mufflers accidentally. I’m wondering about your comment on taking the mufflers from a “sudden drop” to a more gradual grade throughout the system. It would seem to me that the sudden drop from the riser may be more important than what goes on post-muffler. Many boats (mine being one of them) have significant length of exhaust hose running perfectly level with the hull and no mufflers…….so I wouldn’t trouble yourself with the concept of trying to aid the flow of the exhaust water via the grade of the system. I don’t know much about marine mufflers, but I’d be concerned that they may have been positioned with that pitch for a reason. Maybe the restrictive qualities of the muffler require a steep angle to help evacuate/drain post-shut-down water.

Also, re: running the motor on the hose, I’m sure you’re doing it properly but, just in case……….don’t turn the water on until after you’ve fired the motor and, likewise, turn the water off before shutting it down. Dry-running the motor for the brief period before and after turning on/off the water is much better pushing water in when it’s not running. This is precisely why Robert suggests the method of a bucket pick-up…..closest thing to the real thing."
 
"Thanks guys,
This weekend


"Thanks guys,
This weekend I will:
1) Reposition the mufflers to their original height and do a test run, then check for unwanted water.
2) Incorporate the bucket method with the mufflers in their lowered position. Do a test run and check for water again.
3) Epoxy the orings and inner sleeve regardless of the results of test 1/2."
 
"And be reeeeeal careful when

"And be reeeeeal careful when firing up the engines after they have been sitting. Listen carefully to the sound of the starter as you first crank her over (and do NOT try to start it). If it goes RRRRRRR then all is well, but if it goes RRR-hesitate-RRRR then STOP. That's water in a cylinder. Pull the coil wire from the distributor, ground it to the block, and bump her over until the motor goes RRRRRRR again. Then plug the coil wire back in and start her up.

Important!

Jeff"
 
Standards for marine exhaust s

Standards for marine exhaust systems with or without mufflers is for 1" of drop minimum for every foot of run in a continuous downward ditection (no dips). Most muffler manufacturers want to see that same pitch (min) for their mufflers. Some muffler manufacturers also have a maximum pitch. Go online to your muffler manufacturer's website and look up their installation specs.
 
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