2000, 502 mag minor upgrades
 

Right now I have a 2000, 32 fountain fever, 230hrs. What would everyone recomend? Want to keep as much stock as possible, but would like to get a few more ponies! I am thinking headers and ecm tweeks! Any other ideas? it looks to me that the lightning headers are the way to go, due to cost. CMI seems way to expensive for HEADERS! keith-eckerts to due ecm possibly? AZ speed is way to expensive pushing a grand to set them up. Any help and ideas would be great, also no blowers i did that 2 my last boat and even with it set up right i was always paranoid!

Better check your hatch clearance before you spend the money only to find your hatch won't close.
A friend has a 2000 32' with HP500EFI's. His hatch has a large insert to clear the CMI headers.
I have SM exhaust and no problems. About same height as stock exhaust.

Your not going to get much if any out of ECM mods. The only benefit would be to up the rev limiter and turn it harder. CMI headers are well worth the money. I have not had any good luck from Lightnings. On the other hand, I have used well over 100 sets of CMI's and have had no problems. You can find a few Hp by working with the intake. The only real way to find any measurable hp gains is to either supercharge or do internal modifications. Probably not what you wanted to hear, but it is the truth. Hope this helps.

if i dont gain much in ponies at least i can get rid of the weight. I know u cant do much with the ecm's but i can clean them up a touch. what headers should i use from cmi on a stock 502 and want to keep same exahust outlet, and fit under the hatch. us1 how much did you gain w/ stainless marine?

Unless you are planning future upgrades for more HP, then the $$$ for the speed gain are not worth it IMO. Exhaust and ECM recals will run you 8k for maybe a 2mph gain on the top end.

Changing out the stock cast iron exhaust is always a great place to start. I run Stainless Marine on my 502MagMPI.
A good HP exhaust manifold system will give you better mid range power and 100-200rpm extra on top. Headers like CMI E-tops will not gain you much more than a set of Stainless Marines.
You do not need to recal the ECM with just an exhaust change. Maybe up the fuel press a little if you go with headers.
Long tube headers with a cam change could give you another 100HP.

My 2 cents worth
 

I was seriously considering a set of Lightnings this past spring. After much research and question asking I went with Danas instead. GREAT performance and no worries about cracking. I have a 454 "Mystery Motor." One of its previous owners had it re-done by an independent shop so I have no idea what's in it. What I DO know is that after installing the Danas, an RPM intake and re-jetting the stock 750 Weber she outran a Raylar 496 in an identical hull this past summer. Well worth the investment, IMHO. I'm happy!

listen to griff... he's right. when we went thru all this on this forum some time ago, it was noted by many ( accurately) that the amount of hp gain nec to increase your top speeds significantly...i.e 4 or 5 mph on a big boat is something not less than 100 hp per motor. on mine ( same motors as yours but a 38 gun) was going to something like 125 hp/motor...

if the motor has the stock iron manifolds, those are worth getting rid of. leave the injection alone and listen to griff.

youll be far better off

If you really want to do an exhaust upgrade, check out Revolution Marine. Great bang for the buck.

Other than the weight savings and not having to worry about the risor gasket leaking and dumping water in the motor....... natta, zero, zilch.....no speed gains, which I expected.

Zach, you know your boat is stern heavy so ditching your cast iron anchors for manifolds will always help. You could also just throw people overboard and leave the cooler at home when you want to go fast!!! I guess i just like the blingin looks of the imco's over the stock chit. C ya on the lake this weekend:ernaehrung004:

ur damn right u will sat and sunday

Has anyone on here tried the revolution marine manifold's. I think they would be nice for this application because they are similar to stock except for the dry joint and being aluminum. seems too good to be true for $1k a pair. I called them up when my merc 420 manifolds killed my new motor and they never returned my call.....????? what's up with that?

My father installed Gil headers (he has silent choice), with the oversized flame arrestors and had the ECU re-programmed by Tyler Crockett. He picked up 200 to 250 rpms, and a solid three miles per hour (the motors are 502/415 - year 2000)

so.... you really believe that the manifolds, flame arrestor and ecu deal were worth about 75 hp per motor ? or roughly
18 %. because if you are talking about going from 60 mph to 63 mph, thats about what it would have had to be with everything else being equal. thats very very impressive if repeatable.

Your boat may need 75HP per engine to gain 3mph, but mine sure does not.
When I had a bone stock 310Hp/7.4MPI in my boat she topped out at about 65mph. I chnage the cast iron exhaust out for Stainless Marine and gain 150-200rpm with the same prop, up 2-3mph on top.
Then I swapped out the 310HP 7.4L for a 415HP 502MagMPI with the same Stainless Marine exhaust.
My boat now runs 75+...:D
So the 105Hp increase was worth 10mph. If my math is correct, that is 10HP for every 1mph gained.
So I would say that the Stainless Marine exhaust will give you 20-30HP over the cast iron stuff.
I believe, and I'm not alone with this opinion, a better flowing exhaust system is first place to start when you want to increase power...:cool:

you are correct. your boat doesn't need that. and your math is not correct. the hp nec to overcome drag is cubed... not linear... you boat needs less because of the vastly less total drag at 60 than , say, mine which is 14 ft longer and probably 5000 lbs heavier. the post i was refering to above is by a guy with a much longer and heavier boat as well... so i scaled my numbers accordingly. my point is that i find the assertions made by some of significantly increased top speed from modifications that, on their face in most cases will buy a couple of % increase in total power more likely to be based on any number of other factors rather than the percieved gains.

and that was the point of this thread... and i still agree w/ griff. on a box stock 502 injected motor, i don't believe that small , non invasive mods will end up being cost effective from a performance stand point. i base that opinion on 30 yrs of doing the work for real and generating genuine and real hard data results. not someone that knows someone that heard about someone that put a MSD box on and went another 50 mph. and sure as hell some oversized flame arrestor isn't going to do anything at all. the exhaust will be worth 10 a side and the ecu will be worth 10 a side MAYBE... and 20 hp on a 34 ft boat isn't going to buy you as much as paying attention and getting the trim right.

Hey Steve,
You have told us many times that you have 30 years of experience doing what ever you did.
Well my friend I have been boating for 30 years; the last 20 spent owning some 10 different performance boats. Included on that list is everything from a 900lb Hydrostream to a 9000lb Cigarette.
OK, maybe it took +9HP to push my boat from 65 to 66 and +11HP to go from 74 to 75, I'll give you that.

Read the original post again please...

I would venture to say that a 32' Fountain with twin 502Mags has about the same power to weight ratio as my boat.
Base on my experiences with a 29' Fountain single 502MagMPI, a 24' Pantera 330HP/7.4 and most recently a 24' Super, changing the stock cast exhaust will, "get a few more ponies." Changing the exhaust is about the only bolt on that will reap rewards.
This is what I would recommend to do since the post says, "Want to keep as much stock as possible."

Now for the record, I agree that changing the spark arrestor and remapping the euc will not gain much if anything...

pat,
i just can't argue about this anymore. there have been several threads here dealing w/ the " how much power, how much faster" question, some of which i see your name in so you are aware of them. in those the math has been discussed at length. and the math doesn't lie. AND when the purely theoretical math is comapred to some of the "speed calculators" on various web sites as mentioned in those threads. even those numbers agree within a couple of %... the primary differences being in "prop slip" which the purely theoretical math doesn't account for.

but having said all that, i simply maintain that the math as noted below from one of those earlier threads will

a) give a very accurate estimate of the power necessary

b) show very clearly that to get a meaningful top speed increase is going to require a BIG number that is not likely to be found with non invasive changes.

i investigated this for my boat first hand. the number for me to go from the current top speed of 65 to 70 on my boat meant from going from about 850 total hp to close to 1050 or about 100 per side. and i have the same box stock late 502's.

i don't seee any bolt ons or magic beans that would do that or even come close. so for me it wasn't worth it. when it comes time to rebuild them, ill massage that out of them then without any great strain and that will be that.

the following is from the other thread that you were in.

hp = cumulative drag x V cubed ( in ft /sec)

take what the known top speed of the boat is now in mph ...multiply that times 1.46 to get feet/sec

cube that (multiply by itself and then by itself again ) and then divide THAT number into the total HP you have now... that answer is your cumulative drag figure at THAT speed.

now just work the formula backwards.... divide your NEW PROJECTED hp by that drag figure, and do the cube root of that for your NEW mph in f/sec.... divide that by 1.46 and get mph.... and it will be VERY very close to correct.

or for the example we are talking about here, use the hp you have now vs the NEW top speed that you want ( in fps)... that way you get a direct answer in hp required and don't have to find a calculator that will do cube roots.

http://www.go-fast.com/boat_speed_predictions.htm

So what does a 32' fountain weight?
6500-7000lbs
with 830pshp 79mph
with 890pshp 82mph

24' Super
3700lbs
with 310, 65
with 340, 68
with 415, 75
with 445, 78
These are vary similar numbers that I have seen in the real world. 77.8mph is my best top speed to date.
So I guess the exhaust change is worth, "a few ponies"

Steve, you may want to consider changing your cast exhaust. It would give you 2mph...

38' Cig
10,000lbs
with 830pshp 65mph
with 890pshp 67mph


Hmmm...:cool:

Back to the original post, any exaust change is going to be a increase, (power to weight ratio and exaust flow) just get rid of the cast stuff, other than that, make sure your props are running properly for you, a little adjusting on them can help alot.

the boat came with gills already. please note that the weight is only one small component of the total drag... thats why that formula is condensed to that point. the real formula has a great many more variables but since we are considering an " apples to apples, those variables fall out ( so to speak). each boat has its own drag profile on that day and moment in time. my boat , for instance will be much slower w/ full tanks then w/ out... why ? because it will sit lower in the water and have much more parasitic drag. thats why just comparing lengths and and weights is not a valid comparison. a bad 24 ' lightweight hull will have a higher drag profile than a well designed slippery heavier 30' foot hull. thats why everybodys gains will be dependent on their boat specifically. but again... having said all that, once you start going really fast... over 60 mph ... the drag numbers get really big really quick. and thats where a lot more power is required... WHICH is not available ( in my opinion) from bolt on bells and whistles. the exhaust is the single real exception to that rule as you point out. they are heavy and they are horribly designed. putting ANYTHING else on actually FIXES a problem and is worth doing. beyond that tho i think its all just throwing money away as the dollars spent per performance gained ( again in my opinion ) doesn't justify it. the single biggest improvement i got on my boat was by increasing the airflow thru the engine compartment by an order of magnitude. that reduced the inlet temps hugely, the inlet manifold temps hugely and stabilized the oil temps precisely.

that bought me substantial performance.... NOT because i was making MORE than the 425 that the motors started out with but because they wern't breathing 150 deg contaminated air anymore and only making 395 or so as a result. all i did was make them work properly.

i just ran your numbers backwards... at 445 the numbers suggest for that drag profile as derived from your base line , a predicted top speed of 76 mph give or take... less than a 2 % error.... thats all you can ask from these sort of rough numbers.... thats 135 hp to go 13 mph faster... or more than a 43 % increase in power required for about a 20 % increase in top speed....

if we assume those sort of numbers are representitive you are talking about 830 x .43 or 356 MORE hp nec to go 13 mph... in my application, or 178 a side.... and if you plug THOSE numbers in and work them backwards into my original estimate of 125/side to do 10 mph youll find them almost spot on....

so... you see ? your observed data supports the math completely.

Steve,I have talked to smartys dad on the phone and the difference between his 34 ft boat and most others is it runs around 90 mph with stock 502's because of the light lay-up and race hull design so my point without getting into co-effiecient of drag or anything else is that it is a extremely fast boat to begin with that responds very well to small changes unlike most other boats so anything is possible,Smitty

of course. absolutely correct. but the drag profile for THAT boat will remain consistant for that boat. you could find their drag number using their 90 mph numbers and 502 power as it sits and very accurately predict what their boat would do with whatever power increase you gave it. thats all im saying.

not trying to sell anybody anything. just keep the mythology apart from the science.

Hey guys,
We can go around and around in circles. I think in the end we agree to some point. Whether we’re talking theory or practical experience, adding a little bit of power is going to push a boat faster to some degree.
Obviously making a small upgrade like better flowing exhaust (20-30HP) is going to help more on my little 24' Super vs. a 38' Cig. In this case, a 32' Fountain, probably somewhere in the middle.
The man asked what to do to gain power while leaving his engine basically stock. My answer is still the same; change the exhaust. Now if the 2-3mph increase is worth 2K per engine, that's up to him to determine.
Happy Boating.

Actually you MULTIPLY your new projected hp by your drag figure since you are backing it out.

I was going to stay out of this one since it was already way off-topic now but I couldn't resist trying the formula. :D

My boat runs a consistant 70mph with a stock 502 mag. I used 445hp since this is suppose to be the crankshaft hp #. This gave me a drag factor of 2398.792. With 500hp my boat would have a projected top speed of 72.76. If I use pshp I get a projected speed of 72.82. I would hope I would gain more that 2.6-2.9 mph! I have used the speed calculator before and have found it incredibly accurate IF you use accurate data to get your constant. Speed calc says 74mph using crank numbers and 75 using prop hp numbers.

Regardless this debate got started saying a boat needs 18% increase in power to pick up 3mph. This is simply not true "across the board". Some boats it is, but others it is not. And more importantly not true for the Fountain in question. Which is why we have these formulas and calculators.

I don't know what his fountain weighs or what the current speeds are. But I would guess that 60-80hp should get him 3mph. However, will exhaust give you the hp needed? IMO no but as Pat stated what else is there if he doesn't want to get into the engine?

I'm out! :D

no. hp = drag * v cubed.

if you know the drag and you know the v cubed, your NEW v cubed will be the NEW hp DIVIDED by the same drag number.

and what the number show absolutely is that getting the drag down in whatever way you can is a lot more effective at buying you speed then just adding more power. and a lot cheaper generally. for instance... i just stopped being stupid when i gassed up. i started by always filling... duhhhh boat slowed right down. i started doing 1/2 fills.... boat came right out of the water and drag went down and everything was much better. simple and cost me nothing.

none of these calculations are aimed at having a 0 % margin of error. they are aimed at the decision making process.

this is what i have

this is how fast i go

this is how fast i WANT to go......

is it cost effective to make the power to do it ?

if the numbers say you need 50 hp... then it doesn't matter whether its really 55 or 45.... all it means is that it is an easily achievable number. if the number ( as was my case ) was 125 hp per motor or more, then that told me everything i needed to know about the cost effectiveness of that decision.

You originally had to divide velocity cubed by your horsepower. So, you have to MULTIPLY to work it backwards.

70mph x 1.46 = 102.20(Velocity)
Now cube that number = 1067462.648
Now divide that by current hp, 1067462.648/445=2398.792

To work it backwards using the drag number

MULTIPLY, NOT DIVIDE your projected hp by the drag number, 500x2398.792 = 1199396.233
Cube root of 1199396.233 = 106.24
Now DIVIDE Velocity by 1.46 = 72.76

It's a decent formula but I'll stick with the speed calculator. More accurate and MUCH easier! LOL :D

your algebra needs work.

if you divide by hp you leave nothing on that side of the equation and end up having to move the drag number to that side as an inverse function.

hp ( 455) = d * 70 cubed ( don't even bother going to fps...)

455 = d * 343,000

455 / 343,000 = d = .00132

so working backwards from KNOWN d and hp

500 = .00132 * v cubed

DIVIDE 500 by .00132 to get V cubed = 378,887

cube root 378,887 = 72.04 mph

Ahhh, my bad I read this incorrectly:

I did the opposite and divided the hp into the total number(343,000/445=). And FYI since we are using the same numers you get the same answer no matter which way you divide them.

Like I said, I'll stick with the calc since it's faster and more accurate! But that is a nice formula and it was nice to strain my brain!

The 34' Phantom with 32" Bravos was turning 4900/4950 rpms before changing from cast-iron exhaust to Gils. ECU were reprogrammed to increase the rev-limiters, and what ever else Tyley Crockett knew that would help (boat still idles at 650 rpms), the larger flame arrestor is more aestically appealing and may gain only some minimal power.

Ther bottomline line is that the same 32" Bravos are now spinning 5100/5150 rpm. The boat was a consistent 84/85 mph boat, now it will run 87/88 mph consistently.

That is the gain in speed gain my father experienced from these changes, as far as how much more hp was gained is ????? Don't know hp gain.

I don't know exactly how much the Phantom weighs, ask Will Smith at Phantom Boats.

Hope that clears up any confusion.

If you want to get some better info modifications, ask Smitty, "Artic Friends," he is very knowledgeable with 502 MPI's and engine mods, he knows his chit!

I have spoken to both Tyler Crockett and Mark at Precision EFI about the ECU for a stock 502MagMPI.
They have programs that will give the engine a little more kick if you are willing to run 91 octane. I'm assuming the timing is changed along with upping the rev limiter.

Rev limiter was increased to 5400 rpm. Boat runs on 89 octane.

I agree. Even though you were to add an upgraded aftermarktet exhaust to a stock engine you may not see a big increase in top end speed as you would like, but where you just might feel it in more places than any other is in the midrange cruising speeds. I have often heard of guys I know who have bought something like a GIL exhaust system and bolt them on without any other mods/changes and say something like, "I didn't gain much in speed on top, but I saw a very noticable difference in the midrange cruising speeds and throttle response/torque."

For the guy who's just learning about this stuff. These stock cast iron heavy exhaust manifolds that you normaly see on these lower grade engines are obviously adequate enough to fulfill the manufacturer's power output goals i.e. just enough to get the job done.

I have had to learn since the early 1980's that having or adding a better breathing exhaust system is the first REAL step in gaining any kind of power or potential for power----even if you only gain very little on top.

I used to hear the 1960-70's term "Free Horsepower" by adding a better breathing exhaust system. The idea being that by adding a better breathing exhaust you will make more horsepower or at least creat a platform for creating more horsepower as you upgrade/modify the engine. Of course we all know that a marine aftermarket exhaust system isn't exactly free. Generaly speaking, once a better breathing exhaust system is installed, then the better the engine will respond to any mods/upgrades thereafter.

Sorry for being so long winded. Have fun :)

Did the exhaust sound make much of a difference? Which model did you replace with ?