help me open up my exhaust on a 115 HP

[kryan2]

I have a 1979 straight 6 @ 115hp. Is it easy to make it a "top water" exhaust? Do I have to purchase any parts? Do I "just" cut a hole in the lower half?

Any advice is appreciated!

Thanks

kryan2

[dan agnew]

as with all stock stuff they have a innerliner that can be removed. you can just cut a hole above the water line but it will respond a little more with the effort of removing the liner.
most cut the hole on the sides above the lower unit mounting surface. one thing is for sure they will talk to you when opened up. the i-6 has a unique sound unmuffled.

Danny

[Superdave]

Don't drill holes in the side of the exhaust housing. I've had several crack from the bottom mpunts up to the hole. I've had good luck out of drilling several 1/2" holes in the back. I made a layout with 20 1/2" holes, 4 rows x 5 long. 2 rows on each side of the center section. I also drilled the holes at a slight angle to aim the exhaust down.
Dave

[Raceman]

I agree with Super D. The inline housing doesn't have the meat in it that a V6 does and is very susceptible to breakage if you drill it. On top of that you'll see absolute ZERO performance gain by relieving the exhaust on that engine. An 1150 doesn't have exhaust restriction issues. It will make more noise, but that's it.

[kryan2]

I am going to leave it alone.

Thanks to all who took the time to reply!!

kryan2

[JOHNNYGUN]

i've spent way too many hours rebuilding l6's, but along the way, i've found some tricks that actually work. drilling the liner doesn't really give ya anything. but it doess sound cool. there are some things you can do under the powerhead, though, that will improve flow. the last one i did, had some pretty cool stuff done to the exhaust ports, and some material removed at the adaptor plate. i had it on a dyno, and it was puttin' out just shy of a stock 150 v6:cool: every time i'd fire 'er up at the sand bar to take off, i'd get some real funny looks:D she sounded pretty tough:D

[Superdave]

The holes I mentioned are drilled in the BACK of the housing, not in the sides. If you need I might be able to find a pic or something.
Dave

[kryan2]

I would love to see some photos!! (if you dont have to dig out an old computer to find 'em that is)

Superdave.......if you have the time I would like some "inside" info on how to bump it up to 148.5 HP....

Thanks guys

Kryan2

[Raceman]

I think you've got a lot better chance of hurting the performance of an old inline by screwing with it, than helping. I got my first 1500 in 75, a used 73 model. I've had countless XS's since, I'd guess well over 20, maybe more. I sent one to Quincey Welding once. (the builder of the Quincey loopers and numerous outboard specialty parts) The port work was beautiful, the piston window work just as impressive, the reed machining was a work of art. There was only one problem.....the boat didn't run faster. Somebody told me if I'd get a T2 mid to bolt it on, with the different exhaust tuning it'd be faster. It wasn't. I even stuck a 1500XS powerhead on a T3 housing with a T2X adapter. It lost 2 MPH and didn't want to get on top. There've been more inline 6's ruined by Bubba down at the motorcycle shop with his majic port timing formula than can be counted. The reason for the demise of the engine is simple: It had reached a plateau in development that was impractical to pass because of design limitations.

[kryan2]

Like I said earlier......."leave it alone!"

When am I going to learn....I'll tell ya when. When my good running motor is full of drilled holes and water leaks...thats when!


Thanks again guys for all the replys

kryan2

[JOHNNYGUN]

i will agree that any mods made to the inline six, shortens the life. alot of the "bubba" tricks where found on my own, usualy with a lefty hangy out my mouth, when i was a teenager with nothin' better ta do:cool: there are ways to rebuild them, for durability, that don't make them run any stronger. but it's a good engine. i love the way they sound, and the way they look. but i stopped tryin' to get more power out of 'em a long time ago.

[Jeff_G]

You would be better off getting a 1500 block. The 1500 had the best acceleration. The XS had a little more top end. Putting the xs on a T2 mid section may help acceleration at mid range a little but does nothing for top end. Also harder to start and loses low acceleration. This is a wide open exhaust. The real benefit is no motor mounts, solid. There are a few internal mods but nothing you would want to do unless you are racing. Balance and boat set up, props are more important than any mods on the inlines.

[killerpirate]

Edit, sorry very old topic