SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: diesel_lv on December 12, 2013, 11:04:26 AM
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I posted this in Performance boats about a month ago and haven't gotten a response. Hoping someone over here will have some info on this. I have a 4.6 aluminum twin cam ford engine in a 19' Jet. Am putting a turbo (BW S475 1.10 AR 83mm with Air to Water intercooler) on it this winter and want to know if I can run the exhaust out the transom (single) without reversion/sucking water into engine. I will be addding water from engine cooling after the turbo to cool the exhaust, the plan was to run the exhaust down from the turbo then a 90* mandrel bend into the normal rubber tubing then out the transom. The 4.6 twin cam has a bit of overlap due to the twin cam 4valve arrangement. The turbo will be set about 1 1/2 feet above the transom. Should I be ok with this set up without worrying about sucking water back up? Thanks in advance for any help/info.
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Doesn't sound like dry exhaust if you're cooling with water. I don't think gravity has anything to do with reversion. But being a turbo I could be way off. Just my 2 cents
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Maybe wrong way of saying it. Not running logs or snails. Custom dry headers to turbo flange, then turbo, then exhaust from turbo with water run into exhaust post turbo. No, reversion has nothing to do with gravity, it is from the overlap in the cams and as the piston goes down while valve is still open it can create a suction. I know that the snails help keep water out of the cylinders, I was wanting to know if anyone has any knowledgeable opinions on if.. with the turbo being as high as it is, should there be any likelihood of the engine sucking the water up through the turbo and into the cylinders?
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I believe mercury's latest spec is exhaust elbow 13" above the water line. That means the motor would have to suck water 13" up the pipe before it could run down into the motor. They inject water at the elbow and with their cams they don't worry about reversion. That being said you need to find some specs on your cams. They will determine your reversion risk.
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The turbo chargers will eliminate any exhaust pulse that could cause a reversion issue.
I personally don't see any potential issues with it.
One word of caution though, you will still need some form of a flapper, this is only needed if the outlet is completely submerged with the boat at rest.
Otherwise, rock on, sounds like a cool and unique set up.
GT
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Thank you for the replies. I will def be using flappers as the old exhaust cutouts are completely under water at stand still. I figure since it will not be loud, I may as well make it really quiet and a sleeper. Definitely not a racer, but a good solid 50 cruiser.