Cheap 496 mag upgrades (375hp)
01-10-2011, 10:54 AM
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I recently upgraded a 496 Mag to an HO. We opted for the Whipple stage 2 PCM upgrade and added Dana exhaust. I prop shaft dynoed this boat before and after the mods. Stock the hp was 373 at 4800 rpm, 466 ft. lbs of tq at 3600 rpm. After the mods it made 433.6 hp at 5200 and 502 ft. lbs of tq at 3800 rpm. Just for the record, most 496 HOs I've dynoed make around 390 HP at the prop.
Bob Lloyd
Full Throttle Marine
Bob Lloyd
Full Throttle Marine
01-10-2011, 01:39 PM
#82
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Just my opinion but I believe the lion's share of the speed improvement came from the change from way under propped to a correct size and labbed prop. Your hull may be one of those that perform better at higher speed from less wetted area with positive trim provided by the better prop. The rest could be chalked up to the improved exhaust. ~500hp with high flow heads, cam and exhaust on a 496 takes about 50 psi with the stock ECU. The increase in fuel pressure from the stock 43 psi to 48 psi probably reduced power. What do your spark plugs look like? Do you smell raw fuel when idleing/running/on start up?
Last edited by Rage; 01-10-2011 at 01:42 PM.
01-10-2011, 07:01 PM
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Just my opinion but I believe the lion's share of the speed improvement came from the change from way under propped to a correct size and labbed prop. Your hull may be one of those that perform better at higher speed from less wetted area with positive trim provided by the better prop. The rest could be chalked up to the improved exhaust. ~500hp with high flow heads, cam and exhaust on a 496 takes about 50 psi with the stock ECU. The increase in fuel pressure from the stock 43 psi to 48 psi probably reduced power. What do your spark plugs look like? Do you smell raw fuel when idleing/running/on start up?
01-14-2011, 11:27 PM
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i agree gents with both of your statements.....
what the headers allowed me to do was spin a 26 labbed prop
wich is what gave me the speeds i post
as far as the fuel pressure........ i smell no unburnt fuel
it was a fuel module of some sort that my mechanic recomended
the plugs are fine........
just in the very early spring the back end soots up a bit
what the headers allowed me to do was spin a 26 labbed prop
wich is what gave me the speeds i post
as far as the fuel pressure........ i smell no unburnt fuel
it was a fuel module of some sort that my mechanic recomended
the plugs are fine........
just in the very early spring the back end soots up a bit
01-15-2011, 10:16 AM
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SD Fever is right on the money, 40-50 HP doesn't mean the same thing to every boat. Dana Marine does not make "speed" claims because it would be foolish to do so.
We make a horsepower increase claim. Our claim is based off of countless hours on a SAE dyno with 3 different 496 engines.
From my experience, most peformance upgrades are not done properly due to the lack of resources to the end consumer. Every time we do an exhaust install we do alot of testing before and after. We take a pile of props to the lake and it's on and off the trailer 4 or 5 times before we have final numbers for our customer.
For the record, every boat we've ever done an install on, which is a big list, has seen speed increases. Some as little as 2 MPH, some as much as 6 MPH. Power to weight ratio. It's makes a big difference.
We make a horsepower increase claim. Our claim is based off of countless hours on a SAE dyno with 3 different 496 engines.
From my experience, most peformance upgrades are not done properly due to the lack of resources to the end consumer. Every time we do an exhaust install we do alot of testing before and after. We take a pile of props to the lake and it's on and off the trailer 4 or 5 times before we have final numbers for our customer.
For the record, every boat we've ever done an install on, which is a big list, has seen speed increases. Some as little as 2 MPH, some as much as 6 MPH. Power to weight ratio. It's makes a big difference.
01-15-2011, 04:32 PM
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01-15-2011, 07:06 PM
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SD Fever is right on the money, 40-50 HP doesn't mean the same thing to every boat. Dana Marine does not make "speed" claims because it would be foolish to do so.
We make a horsepower increase claim. Our claim is based off of countless hours on a SAE dyno with 3 different 496 engines.
From my experience, most peformance upgrades are not done properly due to the lack of resources to the end consumer. Every time we do an exhaust install we do alot of testing before and after. We take a pile of props to the lake and it's on and off the trailer 4 or 5 times before we have final numbers for our customer.
For the record, every boat we've ever done an install on, which is a big list, has seen speed increases. Some as little as 2 MPH, some as much as 6 MPH. Power to weight ratio. It's makes a big difference.
We make a horsepower increase claim. Our claim is based off of countless hours on a SAE dyno with 3 different 496 engines.
From my experience, most peformance upgrades are not done properly due to the lack of resources to the end consumer. Every time we do an exhaust install we do alot of testing before and after. We take a pile of props to the lake and it's on and off the trailer 4 or 5 times before we have final numbers for our customer.
For the record, every boat we've ever done an install on, which is a big list, has seen speed increases. Some as little as 2 MPH, some as much as 6 MPH. Power to weight ratio. It's makes a big difference.
Oh, and you can take "a pile of props" to test on any boat and pick up speed so I say the increases came from the prop dialing in and not the exhaust. Not all of us have access to piles of props.
That is money well spent but it didn't come from the exhaust (IMHO)
Last edited by thirdchildhood; 01-15-2011 at 07:43 PM.
01-15-2011, 09:04 PM
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OK, I put CMI Sportubes on an stock 496 HO, NO speed gain, NO rpm change. I dump the 496 and drop in a 525. Giving the benefit of the doubt let's rate the 525 at 540 hp. I added 115 hp. I picked up 9-10 mph. Let's call it 9 mph. That means that I picked up 1 mph per 12.77 hp.
The "no speed, no change" comment is consistent with typical results from putting aftermarket exhaust on the 496. Don't get me wrong.. I love headers but they won't make you go faster particularly with this engine.
But your statment is comparing two completely different engines. Of course the 525 ran better. It also comes in a little more expensive than headers for the 496 :-).
Of course I had to change props but I went from a labbed 26 or 28p Bravo 1 to a labbed 30p Bravo 1. So no change in prop; Only in pitch.
But this is a significant change in prop. You may have stayed with same style prop but you sure as hell can't say "no change" in prop.
Usually, you can't talk guys into playing with props "first". They always want to work with props after they've done something else. Truthfully, you could have done prop work when stock and that would have allowed you to see a gain in most cases.
I'm bumping the rev limiter at 5,400 rpm on a good day at 86 mph. Explain that please. And the aluminum 496 exhaust (my '05 was alum.) is very light so the exhaust swap ADDS weight.
Respectfully, what is there to explain? You added a lot of power and torque. The rev limiter is higher and that engine is able to pull higher rpm's with that prop and in your boat. That makes sense.
2-6 mph on every install? Sorry but no. I already posted links to others who saw NO gain. One dual engine install gained 1 mph. That's almost 10 grand for ONE mph. Something is rotten in Denmark.....
But Dana and bob with the guys have done a lot of prop testing. The answer is "yes" if you know what you're doing from the very beginning of the job and if the customer has a decent boat and if the customer has enough time and if the customer has enough patience and if the customer has enough money and if.........................
Not sure I understand the Denmark thing but again, my prior point was to help you understand that just because someone has the money and desire to install power upgrades, it certainly DOES NOT entitle them to better performance. You can not just say "horsepower is horsepower" when speaking boat language. Sometimes more horsepower does nothing!
Oh, and you can take "a pile of props" to test on any boat and pick up speed so I say the increases came from the prop dialing in and not the exhaust. Not all of us have access to piles of props.
Well, not always. Many times, a boat is rigged from the factory to do just about all it can or ever will.
I'm totally NOT trying to be a smart azz ok but if you don't have access and the will to test a "small pile" of props then forget about upgrading. If you can't swing at least a "slightly" bigger prop than what you have then your upgrades are either entirely wrong or they are useless. The prop ALWAYS has to be a consideration when changing any level of power if you are expecting to see any different speed results.
The "no speed, no change" comment is consistent with typical results from putting aftermarket exhaust on the 496. Don't get me wrong.. I love headers but they won't make you go faster particularly with this engine.
But your statment is comparing two completely different engines. Of course the 525 ran better. It also comes in a little more expensive than headers for the 496 :-).
Of course I had to change props but I went from a labbed 26 or 28p Bravo 1 to a labbed 30p Bravo 1. So no change in prop; Only in pitch.
But this is a significant change in prop. You may have stayed with same style prop but you sure as hell can't say "no change" in prop.
Usually, you can't talk guys into playing with props "first". They always want to work with props after they've done something else. Truthfully, you could have done prop work when stock and that would have allowed you to see a gain in most cases.
I'm bumping the rev limiter at 5,400 rpm on a good day at 86 mph. Explain that please. And the aluminum 496 exhaust (my '05 was alum.) is very light so the exhaust swap ADDS weight.
Respectfully, what is there to explain? You added a lot of power and torque. The rev limiter is higher and that engine is able to pull higher rpm's with that prop and in your boat. That makes sense.
2-6 mph on every install? Sorry but no. I already posted links to others who saw NO gain. One dual engine install gained 1 mph. That's almost 10 grand for ONE mph. Something is rotten in Denmark.....
But Dana and bob with the guys have done a lot of prop testing. The answer is "yes" if you know what you're doing from the very beginning of the job and if the customer has a decent boat and if the customer has enough time and if the customer has enough patience and if the customer has enough money and if.........................
Not sure I understand the Denmark thing but again, my prior point was to help you understand that just because someone has the money and desire to install power upgrades, it certainly DOES NOT entitle them to better performance. You can not just say "horsepower is horsepower" when speaking boat language. Sometimes more horsepower does nothing!
Oh, and you can take "a pile of props" to test on any boat and pick up speed so I say the increases came from the prop dialing in and not the exhaust. Not all of us have access to piles of props.
Well, not always. Many times, a boat is rigged from the factory to do just about all it can or ever will.
I'm totally NOT trying to be a smart azz ok but if you don't have access and the will to test a "small pile" of props then forget about upgrading. If you can't swing at least a "slightly" bigger prop than what you have then your upgrades are either entirely wrong or they are useless. The prop ALWAYS has to be a consideration when changing any level of power if you are expecting to see any different speed results.
Last edited by SDFever; 01-15-2011 at 09:50 PM. Reason: their spell check sux
