WTF! Is this reversion?

[flying tomato]

I have had the exh manifolds off this motor 3 times since putting it together. Motor has a total of 20 hrs on it. These are stainless marine exhaust manifolds, gen 2 (I think).

[flying tomato]

I have pressure tested the manifolds and BOTH manifolds look the same.
I have added 8 inches of inner pipe to the risers to combat the problem. (It definately helped the situation, but it still looks like I am getting water in the exh)

[silverghost]

It sure looks like a mild version on exhaust water reversion to me .

What specific engine is this ?

What sort of cam do you have in that engine ?
Is it a high overlap cam where the exhaust & intake valves are open at the very same time ?
That's usually the main cause of this sort of reversion issue.
The high over-lap cam will allow the engine to suck some exhaust cooling water back into it's head's exhaust ports.

Mercruiser several years ago had a severe water reversion issue on their newer Fuel Injected Big Blocks some years back.
What a mess that was .
Many NEW engines were killed with very little time on them.
Mercruiser had goofed-up BIG TIME.

I also had a friend who despite everyone telling him that he had picked a too aggressive high-overlap automotive type performance cam for boat use~~~he installed it anyway in his Chevy MK V big block.
That engine completely reverted large amounts of exhaust cooling water back through it's exhaust ports and hydro-locked the engine hydraulically bending rods & breaking pistons.
That engine was later nothing but scrap.

The very short & level exhaust outlets on many marine manifolds & SS marine performance exhausts complicates this problem issue on our small boats.

Run your engne a short time and pull a few park plugs to see it they are unusually very clean & white or actualy wet with water droplets & mist.

You might try by-passing at least some of the exhaust water though an additional outlet that is T-d into your engines water dump lines before they go to the manifolds themselves..
Put only enough water through this exhaust system to actually safely cool them. Bypass the rest of this water with a small 3/4 "or 1" Hull thru-hull fitting.

Good Luck !

[BUIZILLA]

whta is the lobe separation of the camshaft your are using?

[maddad]

Hey ft, I am not a engine expert but I'm wondering, is this happening only in that one cylinder and port, or all eight? Is this happening in the water or running on a hose? Is the motor fresh or raw water cooled?

[mrfixxall]

your running bobs cam and if you degreed it than its not the cam..are you using ant exhaust flappers? from the looks of those extensions i would say not..not having flappers will make it look like reversion but will injest water when the engine is off.

Look for a set of keith eickerts manifolds and sell those,,only good for mabe 500 hp..

http://www.keitheickert.com/c-441-big-block-chevy.aspx

[silverghost]

Maddad asks a very good question~~~

If it IS just one cylinder doing this it's possibe that cylinder is mis-firing , or that cylinder's valves are not seating for some reason.

You need pressure from the engine's gasoline explosions in ALL cylinders to force all of the water out and on it's way .

[flying tomato]

No it is not just one cylinder.
No, I do not have any flappers. (I always flush eng after use, so I do not see how eng could get water up the tailpipes on the trailer)

Cam has 235/242 dur
114 lobe sep (proven cam design)

[silverghost]

This very problem is why I like to use some sort of exhaust risers similar to the old "Snail" style Holman ~Moody used on these old boats. The knew what they were doing when they first powered these small boats.
The high risers let the water run downhill & block this sort of reversion.
It woud be nice to have the riser elbows almost hit the rear engine hatch and the angle downward to the slightly lower transom exhaust outlets.
This is sometimes very hard to do with very limited space and a raised outdrive X-Dimension.

[silverghost]

The rubber exhaust flappers are ALWAYS a good idea .
They protect like a one- way check-valve to prevent water from dumping back into the transom exhaust outlets from suddenly slowing your boat down~~~after running fast.
OR~ running in following sea conditions.
They protect from Boat wakes~~~and big waves.
& actually keep water from dumping in those big exhaust pipe outlets while tilting your boat up a ramp an onto your trailer.

There is a reason Mercruiser uses rubber flapper valves in their stock engine exhaust Y-pipes.

[mrfixxall]

No it is not just one cylinder.
No, I do not have any flappers. (I always flush eng after use, so I do not see how eng could get water up the tailpipes on the trailer)

Cam has 235/242 dur
114 lobe sep (proven cam design)

so your saying you never dock your boat either? when your boat is sitting still with the engine off and a wave crashes into the back of the boat you dont get water in the exhaust? or how about when you come off plane and you throw the throttle down you dont think the engine wont injest water..think again, not to be mean but what i have mentioned above will and has happen..

[silverghost]

so your saying you never dock your boat either? when your boat is sitting still with the engine off and a wave crashes into the back of the boat you dont get water in the exhaust? or how about when you come off plane and you throw the throttle down you dont think the engine wont injest water..think again, not to be mean but what i have mentioned above will and has happen..

All the above things Can & Do happen .
The best you can do is to try everything you can think of to do ~ to try to prevent the water from going down those big transom exhaust pipes in all possible situations.

I knew a guy who had two sets of rubber flapper valves.
One inside the SS transom outlets that came with his exhaust tips & those cheap Sudbury hose clamp-on style flappers on the outside of the pipes.

By the way~~~
My boats sit in the water ALL summer long for six months.
This has been going on since the early 1970s~~~
Never had water go down into my exhaust pipes.
I guess I have been lucky ..

[mrfixxall]

All the above things Can & Do happen .
The best you can do is to try everything you can think of to do ~ to try to prevent the water from going down those big transom exhaust pipes in all possible situations.

I knew a guy who had two sets of rubber flapper valves.
One inside the SS transom outlets that came with his exhaust tips & those cheap Sudbury hose clamp-on style flappers on the outside of the pipes.

By the way~~~
My boats sit in the water ALL summer long for six months.
This has been going on since the early 1970s~~~
Never had water go down into my exhaust pipes.
I guess I have been lucky ..

Just so you know,,i have been working on boats for 25+ yrs..i have a shop and a ton of customers that have boats to ,so what your telling me is somthing i already know..


are you saying you dont have clamp on flappers??


FT if your boat's carberator idle fuel circuit is not adjusted correctly it may revert water..does the engine load up @ idle?

[flying tomato]

Hey Fixx, Ghost,
I respect both of you and your opinions. Thanks for the advice. I just bought some Drew Shotgun silencers. Do yall think they will help. I'm thinking about plugging the water jacket at the ends and adding a water dump hose.

Or, kicking around the idea of just going to diff exh altogether. What do yall think about cmi sport tubes????

[The Hedgehog]

Hey Fixx, Ghost,
I respect both of you and your opinions. Thanks for the advice. I just bought some Drew Shotgun silencers. Do yall think they will help. I'm thinking about plugging the water jacket at the ends and adding a water dump hose.
Or, kicking around the idea of just going to diff exh altogether. What do yall think about cmi sport tubes????

I have CMI E-tops and run a pretty big cam. I use the external flappers. I have no reversion.

I am still kind of baffled. Those SM's should do it. Maybe they don't have enough turn down in the risers.