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Underwater thru-hull Ex. fitings... good/bad?????

Old 08-09-2002, 12:36 PM
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Default F233

Secret - Do you think I could talk you into making me a copy of that F-233 advertisement you posted below? I have been looking for old propaganda without much luck.

I am restoring a 1970 F233 currently. I am evaluating power options...what do you have in your boat? How fast is it?

I am considering either the 496 (375hp) or the 6.2liter Merc. (320hp). I really don't want a boat that goes over about 55mph though.

I am also condsidering taking the thru hull exhaust out of my boat as it is just too noisy when we are fishing...

Does anyone know how much performance degredation I will have by routing exhaust through the outdrive? I have been told that this method is the quietest...


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Old 08-09-2002, 01:16 PM
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A friend of mine has a 1970 23.3 , he tells us it's the race version. It does have some sort of huge drive on the back (clubfoot?) , it's got a flat deck and a low windshield. It's his shop boat and he loves it (personally I think it's the boat he got his first piece of a$$ in ) after a few beers he will say if you look at it in the right light you can see the old race numbers. Well to this day I haven't seen anything !
Two years ago he took a warmed over HP500 in on trade and the old Formula needed a motor so there it went ! The motor made a 27 Fountain run 73 but in the Formula it went 56 on GPS.
Now it just has a 310 in it but it's still fun !
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Old 08-09-2002, 02:05 PM
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I also have them. My exhuast tip were flush mount angled down and about half under water. I switched to tip with a little extension on them so I could mount a set of Shotgun Silencers. When at idle, the Shotguns divert the exhaust out their underside which is completely under water. Once on plane, they come out of the water and open up. You may want to mount them half under water and use the Shotguns as diverters.
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Old 08-09-2002, 03:27 PM
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Location: Aurora Ontario
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I ran the exhaust tips on my power play under water at slow speed for 11 seasons,never once noticed an rpm fall off from sounds sweet like an old classic untill you hammer it and then it got LOUD My current ride,a daytona 25 has em down below the water lin as well and it definately doesn't lose any rpm on re-entry so I am not quite sure what Teague was doin,landing on the transom at a 90 degree angle to the water maybe?As for the scum line question,it helps control it because the hydrocarbons are trapped in the water instead of stuck to the back of the boat.
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Old 08-09-2002, 03:39 PM
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One other thing, with the Shotguns, you can hold them completely closed by adjusting the mechanism. Really quites things down if you need. I do this when I take my inlaws out for a ride. Drew Marine says there is enough outlet at the bottom of the silencer to let all the water out just advises not run wide open like this.
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Old 08-09-2002, 06:00 PM
Secret F233
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Brad sure can bud but i just had a realy nasty day at work & right now I'm on myway to LOTO I'll shoot it to ya on moday along with some others have cool????

BTW shes got a 5.7 L & an OMC stringer drive I've got 45 so far but only been out twice just got running last week after a year & a half of resto & repair

see my site theres a little info there but it takes a while to load
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Old 08-09-2002, 06:55 PM
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Default How bout this....

My engine burned up a wire on the exhuast manifold at WOT. Initially I thought I blew it up. The motor went from WOT balls out screaming to DEAD. It was like someone shot the key off.
If I had underwater exhaust I am sure I would have dieseled the motor. ie; Sucked major water back into it.
As it was I was very conserned about that with my above water exhaust. Am I thinking right on this???
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Old 08-10-2002, 12:20 AM
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Ive shut mine down at wide open throttle to check plugs while dialing in the carb. My motor sits high. Not much water can get by if you have the Shotguns or flappers.
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Old 08-10-2002, 12:51 AM
Join Date: Feb 2002
Location: LaPorte IN.
My Boats: 1997 23' WPM Cat!!
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My exhaust exits under water and I also run shotgun tips. At idle it is very quiet and it still sounds sweet at 6300 RPM. I run a pretty aggressive cam and I feel the exhaust exiting under water makes it a little harder to dial in the idle. I can set it on the trailer with the pipes out of the water and it will idle all day. Then when the pipes are submerged the idle gets rough and it needs to be adjusted again. No big deal. By the way my cam is 272/280 duration at .050". If your set up is a mild motor it should work great.
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Old 08-10-2002, 01:10 AM
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Only thing I have to say is consider welding the long radius elboes to the inside of the tips and make sure that the top of the elboes is above the water line. This way if you burn up the connector hose the boat doesn't sink.
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