Ski Nautique Y-pipe exhaust |
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gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 943 |
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Posted: May-13-2018 at 11:41pm |
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As part of the rebuilding process, I am getting rid of the inverta-flo and installing a y-pipe, straight through exhaust system. I know it's not very popular with most of the CCF folks, but let's face it, we all know I'm not your conventional CCF thinking guy.
Anyway, as such it's not an incredibly common topic. I've done my thread searching and read what there is out there and until recently I figured it was fairly straight forward. But something came up in a Fish Nautique thread recently that got me thinking so I thought I'd ask the group to get some input from those who may know a bit more. The question is if I need to be concerned about water reversion with no muffler or inverta-flo and the stock GT-40 risers? I'm thinking that the exhaust is well above the water line so I should be good, but a little more input would be appreciated. Thanks |
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JCCI
1995 Ski Nautique GT40 |
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SNobsessed
Grand Poobah Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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You might consider putting a flap on the outlet, to prevent a big wake from pushing in.
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gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 943 |
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Thanks Chris. The boat had a flapper when I bought it. But I haven't inspected it very well, I may need to replace it.
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JCCI
1995 Ski Nautique GT40 |
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gun-driver
Grand Poobah Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4117 |
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You might as well leave the back seat out for the extra room as no one will want to sit in the back seat anymore, it's obnoxiously loud. I have straight hose/pipes on my '85 and I'm putting mufflers back in. Just say'in
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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Riding around in the back seat of a ski boat is a crummy ride with or without muffler(s)
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Riley
Grand Poobah Joined: January-19-2004 Location: Portland, ME Status: Offline Points: 7952 |
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Crummy ride in ski boat better than no ride in ski boat.
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JoeinNY
Grand Poobah Joined: October-19-2005 Location: United States Status: Offline Points: 5697 |
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Its not that uncommon at one point I am pretty sure the boat dr was selling a kit at my correct craft parts and race city marine also installed one or two IIRC. Search the older posts and you will probably find a picture, or give the boat dr a call. Keeping a flapper is not a bad idea. |
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gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 943 |
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Thanks Joe - got the new Centek Y already and new 3 1/2" HD exhaust hose to make the connections. I was just curious if anyone had experienced any problems associated with reversion since it's basically just straight through pipes now. Searching the older posts as you suggested, most of the installs I've found don't appear to have anything more than I will have, save one that had in line mufflers.
And though Paul may be right about it's ultimate sound level, I'll take my chances. I can always add something later if it's too loud for us. |
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JCCI
1995 Ski Nautique GT40 |
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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I am currently working on a pair of v hull boats both with log exhaust manifolds and no mufflers. I am heavily counting on my flappers to prevent reversion.
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gun-driver
Grand Poobah Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4117 |
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Hollywood I had Edelbrock logs on my ‘85 with straight pipes no snails with no problems. I did have new exhaust flaps on the outside though.
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21141 |
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Reports of logs being susceptible to reversion (even combined with no mufflers or flaps) seem a bit exaggerated... otherwise, I’m not sure how so many of us with older boats configured that way have escaped this reversion epidemic for so long.
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Plus 1. I can honestly say I have never heard of a "reversion" issue even back in the days of logs, straight pipes, no snails and no flappers. My X55 is a good example. . |
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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I wouldn't be too concerned in flat bottom boats where the engine is higher up off the water.
Someone like Gary or Ken might be able to find the spacers used even on PCM pyramid manifolds on the Fish. |
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Riley
Grand Poobah Joined: January-19-2004 Location: Portland, ME Status: Offline Points: 7952 |
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Is the engine lower in the water in a BFN?
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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Yes.
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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I didn't limit my statement to flat bottoms only. |
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Orlando76
Grand Poobah Joined: May-21-2013 Location: Mount Dora, FL Status: Offline Points: 3108 |
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I still have logs and straight pipes and no problemo.
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1976 Ski Nautique 351 Escort 1993 Ski Nautique purple and black 351 HO PCM |
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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I assume you're talking about a 70s ski nautique?
If so, great, add another flat bottom boat to the list... |
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Riley
Grand Poobah Joined: January-19-2004 Location: Portland, ME Status: Offline Points: 7952 |
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If you're elbows are significantly closer to the waterline than they are in a flat bottom, why not get some proper elbows or PCM manifolds and avoid all that pain when your weekend suddenly turns to saving your engine because it filled up with water?
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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But I ski weekdays too...
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Riley
Grand Poobah Joined: January-19-2004 Location: Portland, ME Status: Offline Points: 7952 |
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Then you have plenty of time to have those cool looking logs.
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21141 |
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The engine is lower relative to floor height in a v-hull like the Bfn but I bet the engine height relative to the water isn’t that much different. All that hull allows the a v-hull to float higher- the Bfn doesn’t dunk the chine by much, whereas the small flat bottoms float with the chine nearly a foot below the surface.
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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I have a feeling this is more an urban legend,does anyone have actual experience getting water in? Someone somewhere probably had a problem with a high overlap cam and over the transom exhausts,some other guys had trouble with big sport fishing boats backing down when fighting fish and then PCM's marketing dept who would sell an engine for any type boat said that their pyramid style exhaust were better than the logs for that reason. We just don't back up hard,we spend most our time going forward.
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13512 |
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So you don't have a v hull log setup nor have you measured. Thanks for your input TRB
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Riley
Grand Poobah Joined: January-19-2004 Location: Portland, ME Status: Offline Points: 7952 |
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That's how photos of both boats look to me. What about the noise levels from lack of mufflers? |
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Orlando76
Grand Poobah Joined: May-21-2013 Location: Mount Dora, FL Status: Offline Points: 3108 |
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I think my cousin’s brother’s first grade teacher’s landscaper SN had logs too. |
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Please support The Cystic Fibrosis Foundation
1976 Ski Nautique 351 Escort 1993 Ski Nautique purple and black 351 HO PCM |
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throttle out
Senior Member Joined: May-11-2015 Location: Chelsea, MI Status: Offline Points: 153 |
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Just an FYI
I literally just did this conversion on my 89 using a Centek y-pipe. I fired it up for the first time yesterday and the sound difference is NO where near what I was expecting. At an idle sitting on the trailer it honestly would be hard to tell a difference, it is ever so slightly louder but more just sounds a bit different. At WFO it could be a completely different ball game but I won't know that for about a month yet as I'm replacing my interior. My buddy's got an 88 SN and his on the trailer is still much louder than mine at an idle, and sounds better as well. My boat slightly edges his out performance wise but man the 88 and older Nautiques sure do sound perfect lol. |
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1989 Ski Nautique 2001 351 PCM w/ 1-1.23
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gt40KS
Gold Member Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 943 |
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Good to hear real feedback from one that not only has done the conversion, but also seems to appreciate the throaty growl of a V8
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JCCI
1995 Ski Nautique GT40 |
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throttle out
Senior Member Joined: May-11-2015 Location: Chelsea, MI Status: Offline Points: 153 |
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I'll try to get a sound clip next chance I get.
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1989 Ski Nautique 2001 351 PCM w/ 1-1.23
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Jonny Quest
Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2872 |
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I love the throaty growl of a V-8 as much as the next guy -- but my hearing is not too good, so I need all the noise reduction available. I replaced my blown-out Inverta-Flo muffler with a new unit when I performed major surgery to the engine a couple of years ago. I wish I could quiet things down even more...
JQ |
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