Good notations & testing procedures.. :) J

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those of us waiting for dana marine exhuast
 

Full throttle marine, very awesome, this is exactly what ive been waiting for, i was very curious as to what the truth was and the fact and fiction of the dana exhaust. the 48HP sounded to good to be true, but i did order a set, or atleast put my name on the list, but now im not sure if $2400 is worth 21HP.. can someone shed some light on this? dont get me wrong they do look awesome and will shed some light.. are they better than CMI's? also im curious with this exhaust will a prop change be needed?

Bob, thanks for taking the time to do this right. Very professional and straight forward.

Nice work, Bob. Good read. One question, to date have you heard of any problems encountered after removing the turbulators on the stock exhaust?

I've not heard of any problems. Obviously Merc puts them there for a reason. Removing them increases the chances for moisture to work it's way back up the exhaust at idle.

Well....that sucks. Its true, aftermarket exhaust isnt worth the thousands of dollars they charge when used on its own. Two mph is great and all, but not for $2400.

I wish I had a set of CMI's to test, but I didn't. I personally believe the Dana's are as good as anything on the market, better than most. The lightnings I used are a very nice full tubular true header. I was surprised the Dana's outperformed them. That speaks well for them. Fact is there are no magic products out there. Eveything works together as a package.

Some boats will respond much better than others with the additional HP. Might be that the additional HP will push the hull to a more efficient ride or raise the RPM enough to get it higher in the power curve.

Here's an example: suppose your boat is turning 4700 RPM at WOT now. You add a set of headers and pick up 300 RPM and 4-5 MPH. You think wow, the headers really made a difference. However what really happened is that the headers added enough power to gain maybe 150 RPM which moved the engine up in the power band to where it generated an extra 15 HP so it moved further up the power band gaining even more HP. The headers only accounted for part of that gain. Had you worked the prop to have it peak at 5000 RPM you would have gotten some of that gain. I believe this is one of the reasons some people see more gain than others from adding headers.

Bob:

Very interesting results, especialy the effects of water in the exhaust and the loss of power through the Bravo drive. As for the exhaust results I can say that all ofour dyno testing was done dry because our facility is not able to run a wet test with our quieting system. I sure would like to see you prop shaft test a Mercury HP525 at the prop with the XR drive. Even though peak power seems to occur in these motors at about 13.6 A/F I dont think I would set up a boat to run there over extended periods. I think I would error on the side of cautiion for long term reliability and set the A/F closer to 13.0-13.2. I love the 87 versus 91 Octane comparison. confirms what I've been preaching for a long time, Higher Octane does not make more horsepower. It only needs to be higher to counter knock if it occurs. Keep up the great testing!

Best Regards,

Ray @ Raylar

Bob -

I wish you would have asked. I'm sure we could have sent you a set of CMI's to test with, although you'd probably want to keep them after you saw the results :drink:

Seriously, nice job with the testing.

Kirk

Great post Bob. Very nicely worded. Great info as well!