keithp83

I was looking to install a thru hull exhaust on my 86 formula 242ls with a 260hp 350. I did some measurements and the end of my risers where I would connect to are 3" then it steps up to 4" with a 90 degree bed in a pipe then connects back down to 3" before it goes down to the drive. So my question is.. Should I just get 3" marine exhaust house and connect it to 3" thru hull exhaust tips that I install or should I connect a 4" stainless pipe to the stepped up exhaust bellow that's on my risers and then connect it to a 4" thru hull tip? ( capping off the bellows that go to the stock exhaust bellows in the drive) are there any advantages to doing the 4" instead of the 3" (performance, less strain on the engine) or is it just personal preference or for higher performance engines? Like I said its just a little 260 by far not a race boat lol but I would love to hear some nice sound out of her and picking up a few extra mphs wouldn't hurt

Mr Maine

I wouldn't mix and match the size, for a clean look you could get some 4 inch risers and go straight out the transom 4 inch all the way. Also you could go 3 inch all the way, but personally I think 4 inch looks better. Performance probably wouldn't be different either way on a 260 horse 350.

Budman II

iTrader: (1)

You will see little if any performance increase either way - I doubt if you will see any speed increase switching to thru-hull on a 350. You will just think you're going faster because of all the noise.

Why not find a set of Silent Choice diverters over in the Swap Shop and have the best of both worlds? I really liked having mine - it was nice to be able to bump it down to thru-prop if we pulled up next to someone and wanted to talk to them, or if we were just cruising and passengers actually wanted to carry on a conversation or listen to some tunes on the stereo. That is one thing that I really miss with my current setup - had to ditch it when i went with headers.

keithp83

I ended up with a good deal on some 4" thru hull tips so looks like im going with a complete 4" system lol I took your advice and visited the swap shop and found a good deal on some diverters. I PMed him and asked what the dimensions were and he told me 3 3/4? does that sound right?? also his appear to be oval where they connect to the y pipe and mine appear to be round. any help would be great I'm lost with this lol

keithp83

http://www.offshoreonly.com/forums/s...e-exhaust.html

heres the link to the classified

Budman II

iTrader: (1)

I don't know about the Corsa's - I ran the Merc Silent Choice setup on mine which have cast aluminum diverters that are actuated by air cylinders, powered by a little compressor pump. Those connected with standard 4-inch exhaust hose. I suspect the Corsa's will do the same. Yes, some of the Y-pipes had round openings and some were oval. I think the rubber boots are flexible enough to conform to both shapes.

SB

iTrader: (1)

I have a sbc boat out there with 3" full wet exhaust exhaust amost touching 70mph. Sounds great....tad quiter than the 4". 4"-3" Reducers where installed right at the 'tips' connection inside boat.