exhaust elbow tube extensions - slash cut questions
#11
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Eddie flares the end to shoot the water towards the wall of the connecting hose.
But yes, the shape allows more air to come backward during overlap and low rpm.
I bent my lower flat to get rid of the easy transition for water (most will be on bottom) to come back into the inner pipe, that the flaring would create.
A flapper mounted in the dry section of inner pipe would be ideal, however, I know of nothing that could do this quietly and survive. LOL.
But yes, the shape allows more air to come backward during overlap and low rpm.
I bent my lower flat to get rid of the easy transition for water (most will be on bottom) to come back into the inner pipe, that the flaring would create.
A flapper mounted in the dry section of inner pipe would be ideal, however, I know of nothing that could do this quietly and survive. LOL.
#12
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Bending the bottom part you mentioned makes sense.
The flare - yeah you wonder which works better, the flare to direct water out to help stop reversion, or the flare at the same time actually lets more air in backwards(which will have water vapor with it) and makes rev worse.
On things like this you never know which will work. Even will all the info and ideas ya'll have given me to go in the right direction, I think a few trial and errors are coming. But i'll try on one motor by itself to see what works.
thanks.
The flare - yeah you wonder which works better, the flare to direct water out to help stop reversion, or the flare at the same time actually lets more air in backwards(which will have water vapor with it) and makes rev worse.
On things like this you never know which will work. Even will all the info and ideas ya'll have given me to go in the right direction, I think a few trial and errors are coming. But i'll try on one motor by itself to see what works.
thanks.
#13
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From what I learned from previous post, that is kind of how i was doing mine except using aluminum inner with rubber hoses outer, and using a slash cut on the inner.
If that doesn't solve it, I will try a flat cut with a flare like you show here. I know the Mercruiser 496 certain years had a flare at the back of their stock elbows, so must be something to it.
If that doesn't solve it, I will try a flat cut with a flare like you show here. I know the Mercruiser 496 certain years had a flare at the back of their stock elbows, so must be something to it.
#14
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Actually further info, my boat, like some others, have low mounted engine (compared to water height) and thus low mounted tails that plunge under water at times due to big waves and etc. I wanted a step ust in case flappers wheren't fully closed or if one broke off without knowing it during an outing. Boat comes back on land each time, so I see if the external flappers are still there or not. So, some though for possible intrusion was on my brain too.
#15
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Boatally Insane / SB
Is the open ring area about 1/4 or 3/8 tall, between the inner/outer - right at the left flare at the weld - is that completely open upstream? or is there some metal in between that helps to collect water and keep more water up all around the inner tube before flowing out the rear and meeting the gas.
Is the open ring area about 1/4 or 3/8 tall, between the inner/outer - right at the left flare at the weld - is that completely open upstream? or is there some metal in between that helps to collect water and keep more water up all around the inner tube before flowing out the rear and meeting the gas.
There IS a piece of metal welded in between with a gap at the top. It's not welded solid, so it forces the majority of the water out the top of the pipe, yet allows the tails to drain when the engine is off.
The angle / location of my transom mounted tips did NOT match up to my new exhaust outlet location, so I "wallered out" the holes, installed some lengths of pipe and sealed it with 4200 and a trim ring at the transom.. so now, I don't have to worry about melting hoses..
Last edited by Boatally Insane; 05-19-2016 at 12:17 PM.
#16
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That one is a little different than what ive seen before.
I ve seen just the opposite too - some try to block it off at the top just to try to keep the gas away from the water by making the water run out just the bottom. May have helped a little but did not solve it. In your case the water will be all around but hopefully the flare helps.
Is that the very end of your exhaust out behind the transom, or is there an outer pipe that goes around that inner flared piece??
I ve seen just the opposite too - some try to block it off at the top just to try to keep the gas away from the water by making the water run out just the bottom. May have helped a little but did not solve it. In your case the water will be all around but hopefully the flare helps.
Is that the very end of your exhaust out behind the transom, or is there an outer pipe that goes around that inner flared piece??
#17
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Man this exhaust stuff gets deeper and deeper.
It almost seems as though if there is going to be reversion .... theres going to be reversion if water is mixed at all. Its seems as though its mostly the length of the inner pipe from the elbows that mostly does the trick with the flares and blocks maybe helping a little. All this in an effort to try to keep from having to go to dry exhaust.
It almost seems as though if there is going to be reversion .... theres going to be reversion if water is mixed at all. Its seems as though its mostly the length of the inner pipe from the elbows that mostly does the trick with the flares and blocks maybe helping a little. All this in an effort to try to keep from having to go to dry exhaust.
#18
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Why are you having such a reversion issue? What's the engine build ?
#19
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No idea. Trying to find out why.
Except after finding 3, or maybe 4 Mercury service bulletins on the subject, including the one you just mentioned in this thread about adding the trough on the stock elbow it must be happening frequently and even in stock 496's and 502's. It says reversion is due to a "exhaust design",
Mine are stock 502mpimags 1999. stock cams. I don't have info in front of me but checked lift and at least that matched mercury's spec for stock.
only non stock items are on the Starboard motor - i have just rebuilt the heads due to low comp from rusted valves.
I put on H.S. roller rockers since the orig flat tap where worn pretty bad. While i had intake off I shortened the intake runners after discussing with Young Performance and opened up the inlets to the four runners,
and put on new Eddie marine std alum manifolds & alum elbows.
Since rebuild it is running good but still puddles the manifolds and wets the plug threads just like before the rebuild and that concerns me.
Has the same moisture issue on the port motor which is 100% stock and still gets plugs wet and puddles in the manifolds.
they originally idled at 600 but i set them to 675. Above 675 they dont come out of gear easy i think from the spark stabilization mode on the Mefi 3 that keeps the idle smooth and doesn't give it much of a chance for the clutches to separate.
160 thermostat
has recirc water pump
its not intrusion as it does it in the driveway.
has reversion/condensation on the river as well as in the driveway.
I suspect it will get a little better in the hot summer, but this is no good if you cant use the boat in spring and fall, and maybe winter here on the gulf coast.
that is where i am at SB.
Except after finding 3, or maybe 4 Mercury service bulletins on the subject, including the one you just mentioned in this thread about adding the trough on the stock elbow it must be happening frequently and even in stock 496's and 502's. It says reversion is due to a "exhaust design",
Mine are stock 502mpimags 1999. stock cams. I don't have info in front of me but checked lift and at least that matched mercury's spec for stock.
only non stock items are on the Starboard motor - i have just rebuilt the heads due to low comp from rusted valves.
I put on H.S. roller rockers since the orig flat tap where worn pretty bad. While i had intake off I shortened the intake runners after discussing with Young Performance and opened up the inlets to the four runners,
and put on new Eddie marine std alum manifolds & alum elbows.
Since rebuild it is running good but still puddles the manifolds and wets the plug threads just like before the rebuild and that concerns me.
Has the same moisture issue on the port motor which is 100% stock and still gets plugs wet and puddles in the manifolds.
they originally idled at 600 but i set them to 675. Above 675 they dont come out of gear easy i think from the spark stabilization mode on the Mefi 3 that keeps the idle smooth and doesn't give it much of a chance for the clutches to separate.
160 thermostat
has recirc water pump
its not intrusion as it does it in the driveway.
has reversion/condensation on the river as well as in the driveway.
I suspect it will get a little better in the hot summer, but this is no good if you cant use the boat in spring and fall, and maybe winter here on the gulf coast.
that is where i am at SB.
#20
Charter Member # 55
Charter Member
I would get a riser spacer kit to increase the angle http://www.cpperformance.com/p-14191...-93320a13.aspx