BBCLiberator

I saw a post on one of those "other sites" where a guy cut the baffles out of his exhaust and picked up 3mph. Think that's realistic??? I have similar power and see similar speeds (nearly identical actually) he claims to have run before cutting them out so I have no reason to doubt the post

Here is the picture he/she posted and it looks like it has two sets of baffles where I only thought I had one set too so I'm glad I found it posted. All the talk of mufflers in the general forum got me thinking about it.

http://www.speedwake.com/forums/showthread.php?t=72758

Thoughts?

Raylar

That boater is talking about a 540HP 502 built engine and those baffles to gain 3 miles per hour in that particular boat would have to release at least another 40-50Hp to gain that speed increase. If those baffles were choking of that much exhaust flow its possible he gained that much speed in a perfect world. With a stock 340-415 HP 454 or 502 I don't think you would see that kind of horsepower increase so also not that spped incrrease. If they are easy to remove and you can measure by GPS and the increase is there for you, then go for it provided you can handle the noise or noise violations present in your boating area if there.

Best Regards,
Ray @ Raylar

BBCLiberator

Yeah, I also have the 502 (mines .030 over) with a Marine Kinetics Cam, Edelbrock Air-Gap Intake, SM manifolds, full roller valve train with slightly bumped compression (to about 9:1), so I assume I'm at least in the 500 horsepower neighborhood even though I don't have dyno data to back it up. I like the idea of using slip in mufflers and opening it up when needed since the boat is actually pretty quiet with these baffles.

It's interesting he says 67.4 mph before the removal, I see about 66.2 on GPS with a light load. I feel the same phenomenon of it laying over at just over 5000rpm. This could be lots of things.

Maybe I will give it a try.

By the way Ray -- do you know if there is a good way to measure A/F ratio with the engine in the boat, I may be running to much jet in the carb too, but I figured conservative was better. I'm running the stock as delivered 850 Holley mechanical secondary part # 80443, jet sizes -- 850 (F)88,(R)96 6.5,6.5 4150 Marine

Raylar

Talk to Stainless Marine, I am sure they could weld a couple of O2 bungs in your risers and you could then install a wideband O2 sensor kit and measure your air fuels. I would not advise leaving the O2 in all the time, just during testing and tuning, then install the O2 bung plug and boat away!

Best Regards,
Ray @ Raylar

BBCLiberator

I already knew the answer but was hoping for "magic". Guess I'll go get a box of spark plugs and do it the old fashioned way for now. Few hours on the water and a few changes ( jets and one bank of plugs each run) and I'll get it close.

If you see spark plugs for sale with 30 seconds of run time on them you'll know why