Nauti By Nature

What does this sound like ? buyer beware !

the end of second season (under 30 hrs)

installed gibson's 4.5 downturn mufflers

short time afterwards one motor down

both motors head"s got water (steaming into engines )

but not into engine oil . Water must have been sucking

up downturned muffler pipes Gibson says no , I say stay the

F*@k AWAY no way a dry pipe alone could cause water

inverion also my engine builder confirmed that the cam is not

the cause that the overlap would be able to run in wet exhust

as well . Seems like motors got steamed And I got soaked

and these mufflers rated for 1200 horses don"t belong near

any hp motor !!!!!!

CcanDo

What do you think could have caused the problem ?

ROB FREEMAN

iTrader: (2)

i believe he thinking water ijestion caused by the downturns my friend ?

Biggus

iTrader: (1)

I've seen a similar situation but it was a staggered configuration.
On a friends staggered O/L fitted with "donkey dick" downturn tips. When the forward motor was fired up, the exhaust pulses would force water right up the pipes of the close-coupled motor. It took quite a while to figure out where the water was coming from, finally we pulled the headers away from the block and started the forward motor, sure enough the water was being forced right back up the pipes.

Fountain38SC

Exactly what has stopped me from putting them on mine. I also have dry stacks and have heard a couple similar stories. I wonder how many fountains with bigger power they've put trundowns on. Anyone know of any?

CcanDo

We planned on using turn downs.....However,not so sure now.
Thanks for the heads up!!

Now I'm wondering how a bung or two in the turn down,above water line, might relieve enough to solve the problem. Subject to the size of those openings,the muffled effect may still be acceptable.

Thanks Again

Nauti By Nature

Gibson said that this tech is not new , similar to thru prop
exhaust , but I had dry exhaust to avoid this from happening
and they claimed to be able to quite it this way but they sucked water up like drinking thru a straw . they said desiling
could have caused the water to steam thru my exhuast .
pressure tested all cmi stuff no leaks . REBUILDING WITHOUT THEM , i KNOW THAT ! NOT FOR HP MOTORS ..............

STAY AWAY YOU HAVE BEEN WARNED !!!!!!!!!!!!!!!!!!!!!!!!!!!

STARTING NEW THREAD " SILENT KILLER "

CcanDo

We also have dry tail pipes...90* elbow is screwed into a bung 2 1/2" from the tip.

The decibel requirement is more or less an issue from area to area...However,in trying to do our small part,some type of muffler seems appropriate.

Therefore, it is understood Nortech is using a basically dry system that discharges underwater exhaust. They also have a bung or relief port sufficiently above the water line. That bung would effectively create a vacuum leak in the tail pipe. That said,the bung ID VS. suction from reversion/reverberation should eliminate the problem. I recall the Nortech bung as being 1" ID.

Nortech's system theory and yours appear similar. The Nortech design is simply introducing exhaust at a different location in the water and they have a suction leak because of the bung.

A person can't suck fluid through a straw that has a definite hole in the side,above the fluid line.

You have instilled further consideration for Stellings In Line mufflers. However, it would be nice if there were not any welds or joints on the inside of the inner pipe.

GLH

I have never had an issue in the two years I have run Donkey D!cks on my rig.

It is a Cigarette Tiger running Zul's Dynoed at 1040HP the pipes where custom made by CMI and are on 5" pipes. My guess is that if you are running 4.5 inche pipes on anything over 800HP adding the downturn my be the straw that breaks the camel's back in restrictive exhaust, but I am no expert.

Here is a few pics of my set up. Hope this helps in your problems.

hoozeyurdaddy

Nice boat, did the turn downs lower the sound level in the cockpit while up on plane and running, I am install a set on my boat this year and whouldn't mind if it quieted it down a little.