I was thinking of doing the underwater thru-hull EX. fitings for my F233 for the quiet at low speeds & performance on plane. Any words of advice & how do they work????

I remember reading a tech article in Powerboat last year addressing the underwater thru hull outlets. Bob Teague said that the boat was quiet around the docks, but the underwater outlets made for some strange engine behavior in rough water. He said that upon launching the boat off a swell, he found the engines would lose 500-600 rpm when the bottom of the boat contacted the water again. I guess water was forced against the exhaust outlets upon re-entry and greatly increased the backpressure. Teague also noted that this could have some negative impact on engine reliability. Hope this helps...

Racing_Fan

I have under water exhaust on our boat and love it. I have never had a problem with loosing rpm after launching off of a wave and I get the entire boat out of the water plenty . (Just ask THirsty turtle or caincando). We have huge noise laws up here and having the under water exhaust is awesome, .

I have underwater exaust on my 25' Warlock and it works great. At idle or no wake speeds you can hear the stereo perfectly. Mine also has flaps. We run the Mississippi on the upper Alton Pool

Thanks for the info ....I posted a simular question the other day in the tech section......got no response...guess I need to shower more often

Thanks guys good to hear I know a lot of the older F233’s had this but mine does not I guess I’ll start researching the manufacturers. I just love it when the Supra’s & Master-Crafts fire up hear on Lake St Louis the underwater fittings make for such a classy sound kind of like the old Chris Woody’s of yesteryear. Any hu thanks again anyone know a good resource for ex. fittings…….

1966 Formula F233 & Formula jr

When going with below the waterline exhaust I would recomend internal as well as external flaps

www.cpperformance.com has a few fittings...look under exhaust accessories...have seen a few others on dif exhaust manuf. sites..corsa .. stainless marine ..... ect...

Assuming properly tuned engines, will you get more exhaust/scum line with underwater exhaust than above water exhaust?