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Quote:

Originally Posted by Raylar (Post 3500391)

Just to give everyone here some more credible info:

Raylar has dyno tested on ours and other dynos probably more 496Mag and 496HO engines both stock and with our various upgrades, kits and engine packages than almost anybody on the planet.
A stock full y equipped 496Mag makes about 365-380HP at 4800 rpms at the crankshaft.
A stock fully equipped 496MAG HO makes 421-430 HP at 5000 rpms at the crankshaft.
This is on calibrated, SAE standard testing, with correction factors and specific fuel gravity calculation adjustments and these numbers are pretty much spot on - PERIOD!

Best Regards,
Ray @ Raylar

Wow, thats good info, all the info I have seen rates those types of numbers at the prop. If you figure 10% loss that is way over estimated.

Crankshaft versus propshaft horsepower?

I will post this one last time!
I know there is printed and website info from Mercury Marine and others that is confusing and sometimes just flat wrong.
My sources and tell me that since 2000, all Mercruiser (black)engines up to 2010 are dyno tested at the crankshaft on Mercruisers Stillwater dyno's.
The Mercury Racing (Blue) engines in Fond Du Lac are dyno tested on Mercruy Racing dyno's and are rated for approximate horsepower at the propshaft with their drive HP correction factors added.
This is why the HP525efi for example will test SAE on a new properly running engine fully equpped at about 540-550HP on most good dynos at the crankshaft and is rated at 525 HP at the propshaft.

Best Regards,
Ray @ Raylar

Quote:

Originally Posted by jeffswav (Post 3500403)

Wow, thats good info, all the info I have seen rates those types of numbers at the prop. If you figure 10% loss that is way over estimated.

According to the figures I've computed before, the TRS or III with a transmission will approach 10% driveline losses, while a Bravo is 5% or so.

Quote:

Originally Posted by tcelano (Post 3500728)

According to the figures I've computed before, the TRS or III with a transmission will approach 10% driveline losses, while a Bravo is 5% or so.

"5% or so" with both the Bravo X and XR drives?

I looked at the Livorsi site and did not notice an Air/Fuel gauge. I was wondering if their is a practical application for one on a boat?

I found this gauge on Auto Meter's site...

http://www.autometer.com/cat_gaugede...earch&gid=3607

Quote:

Originally Posted by Raylar (Post 3500700)

Thanks, Ray. That is my understanding as well after talking with some Merc reps awhile back at a boat manufacture's rally.

Quote:

Originally Posted by WildRooster (Post 3497847)

I just did a repower myself....had a 496 and researched it quite a bit before selling it and going with brand new horses. I've heard good and very bad stories about trying to beef up the 496. It has cast internals and needs to be completely replaced to make any kind of difference with maintaining reliability. I've got the 25 OL(not the 26) and it's 150 lbs less...and my 496 mag(375 HP) pushed it to 63-65mph at 5000 rpm depending on temp. If you are turning a 26p B1 at 4900 rpm, you should be seeing 70 at least. I'm not a fan of the B1 as it creates azz lift instead of bow lift like the baja hulls require. The B1 is made for a heavier boat. My opinion is if you find the HP and start getting 75-80 mph out of this setup...the B1 will create some issues in handling vs going to a 3 blade Mirage. I'm

Artic, i'm curious about your comment on a 5 blade prop? You think the 5 blade will help in bow lift? Wouldn't it be hard to turn that thing to any rpm's with this setup? If you're getting 560 HP....IMO it should be turning a 25 Mirage. BBlades can offer a more professional than mine.

Reading the posters info he has installed a imco shorty and a box on his boat, when wild card did this he went to a 5 blade prop to counter the prop slip he had from raising the center line. I have never been able to run a mirage 3 blade since turning up my power, even when boat only had 650 hp. A 3 blade is never going to carry the bow on a 272 that has a raised prop center line. I had a box and a shorty on my boat and it really LOST the ability to carry the bow even with a 4 blade, it needed some kind of 5 blade to counter the lost leverage and increased slip but in my case 5 blades lower my slip to the point were the drive shears off shafts almost instantly. He has already raised the drive and to go back would be a real pita and alot of work, he's going to have to find a prop that works the best with higher prop center line and its probably going to be a 5 blade. Stay away from the merc Maximus though as it will make a single torque roll like a sonufa*****, maybe a hydromotive , Smitty

I am running a B 1 26 from B Blades. I have a box,cmi sport tubs,Whipple stage 2 up grade with the low t stat. I run 69 to 70 gps. I have seen 72 @ 5500 rpm. Only once on the st clair river.

Smitty, Started a new thread over on the prop section regarding your comment on the 5 blades props. Please read.

Interestingly enough your 26 B1 and the 23p (Mirage + ??) are at the same slip, 15.5%. What was your rpm at the 61 mph speed? 61 mph was before the motor mods right?, also was it before the box and the shorty? I assume the 61 mph was attained with the old prop?

My old Baja 272 did 65,66 with a 502EFI, 72 with procharger and 78 with procharger, gil exhausts, cam, ported heads and roller rockers.