Repower advice
 

Ok fellow beak drivers. I have a 2000 38 Lightning w/ small steps. I currently have 525sc's that push her 78-81 depending on load, temp, conditions, prop etc. I like my boat and have gotten it where I want it. I want to get to mid 90's. Currently my motors are making roughly 480hp at the prop. One is a new refresh and the other will need it. What kind of HP do I need to get me to my goal? If I cannot get it to run mid 90's I will have to go a different way. I know we have probably beat this horse to death but I am at a crossroad and have to start making decisions on which way to go. Thanks in advance for your comments and help.

6- 700. Depending on how well your boat is set up

420 or 871 blowers, or chilled 250s (bigger is preferred) Get the bottom checked out (blueprinted) -2 Short drives, upgrade gimbles, at least XR uppers, most likely 5 blade props. I would also pull both and do full roller conversion so you can run a better cam (about $4000 for both)

All that being said, you are gonna run the speed of a large step semi stag 525efi boat that could prob be had for less (and most likely more reliable) that what you will spend to upgrade.

Yes I am starting to realize that. Not sure if I want to wrap an additional sum of money into a 14 year old boat.

Bail before its too late !!!!!!!

Don't kid yourself. props. 1600-2500. eith hydro p5x or Maximus.. Herrings are even better but they are 3500 a set. Chad

If im not mistaken the 525sc is a 454 based engine right? Personally if it was mine id throw a pair of 502 short blocks in it have Bob custom Grind your cams maybe re-pulley the blowers if ya need to (I have seen in a friends car where a change in displacement caused boost to drop enough it was necessary). Then blue print bottom and re-prop as necessary. The upside is you can always sell the 454 short blocks to recoup some of the money spent on the 502s. The only big down side to doing It this way is if you do have to spin the blowers harder they will make more heat and or be at their limit.

Those 454 lowers will make 700 all day with a bigger blower and the right cam. If he was going that route I would go 540ci

Let me clarify something. I have had to completely rebuild the starboard motor. When I did I upgraded to roller cam, hydraulic lifters, better cam etc. my engine builder overbuilds. He builds race engines. Got about $12k in that one. Was going to pull both out this winter and upgrade the other engine to match the rebuilt one. Was going to put a 250 blower kit on it from the blower shop. Was also going to put aluminum heads on it and upgrade exhaust. I think roughly $20 k to do it. I will then have $32k in it. Then sell off old blowers 088 heads and anything else I took off to offset cost no matter how small.

Do it right the first time, more cubes equal more power. Blowers and pro chargers are available but when trying to build power there is no replacement displacement. Just my two cents.

Another thought is that as soon as you cross that 600HP the bravo drives are a time bomb especially in a heavy boat like a 38 or 42. You will keep spending money upgrading (replacing) drives until you either get rid of the boat or go to SSM drives.

There is a replacement for displacement........boost!

Skip the 250 and find 420/871. You will need 7 psi of air (overdriven) on a 250 to match the cfm of 3 psi on a 420/871 (under driven) the larger blower will stay cool at that psi and make more power because of less heat. Also safer with the big blower against hot air charge detonation.

If you want to be around 700 hp those head will be fine. I have seen aluminum head 250 blower 509s make near 800hp, which is way too much for your drives.

What drives to you have? If you have standard bravo some will tell you to upgrade (including me) but used bravos and bravo gears are cheap :) you can upgrade or keep spare bravo 1s on hand, cause you are going to need them

For what it may be worth to you,

Had a pair of Merc 525 SC's, had chillers under the blowers, the small pulleys, ran 10 lbs of boost, made 640 +, wasted more Bravos than my wallet cares to remember, all said they ran forever to this day without a hitch so I hear.

I would think that 6+ should put you in the 90's, a 575 SC 38 would run those numbers.

Yeah! :)

you are blowing too much doe on this thing. Put 2 671 blowers and have your motor guy find you a used mf3 fuel injection. That should get you to 90. Then work on set up. Remember. I am the only guy on here w a 2000 38 running a hundred mph with a tweaked set if 575s

So you are saying keep the heads I've got and run a larger blower? Do I run it with an inter cooler? Do I need to upgrade exhaust? I have bravo drives and yes I will keep an extra around.

What would a stock set of 575sc do for it??

Saw it mentioned in an earlier post.. so for comparison, I had a big step, semi-stag 38 with 525EFI's, bravo xr with standard lower and 32P bravo 1 props and it ran 88 tops..

My boat stock 575sci big step, side by side, ran 88 in summer and 91mph in the cool (all time high stock). It has been said the big steps are worth 3-4 mph. A 575sci is easily bumped up to 650 and beyond however, very conservative right from merc.

Your stock exhaust will be fine, should have cmi for that vintage correct? If not even the gil will be just fine.

No inner cooler needed with the larger blower running low boost, it will not make heat. For extra protect get some 120 degree stats and tune your mixture to them. Again if target is 700 hp you will have no problem with the stock rectangular port heads.

That is the beauty of the larger blower. To get the same amount of CFM (air) with a smaller blower you will have to spin the hell out of the 250 and run a higher psi, this makes heat both compressing the air and the letter blower working so hard. Large blower at 3.5 lbs will be ice cold :)

Add some 02 bungs to your risers on the 1-7 bank of both engines, then get a hand held meter to help you tune after completion.

You can also upgrade your stock drives to xr internals and sell what parts you have left over. I am thinking a 10k lb boat with that power will rip a stock bravo apart as soon as you hit the sticks :/ but I dunno. You can also do the xz upgrades and have longer gear life. I had good luck with xz on my 36 Baja OL with blown 500s, never an issue.

NNNaaaaaahhhh cubes man cubes

Compressed air means more air in the combustion chamber, effectively making the engine a larger displacement. Boost is the replacement for displacement, and the next wave of engineering is all about boost in small packages (see Ford eco boost)

No way I would give up the pull and sound of my blowers for bigger ci. N/A, its just not the same.

You have people on here telling him to drop his 454 blocks in favor of 502 ci? There are guys on here (mild thunder) making 800+ HP on 468 ci.

He is trying to make 700 hp, not 1000. 700 blower HP is easy and inexpensive on the 454 platform he has.

Now.....back to those bravo one drives :D

yeah but you can turn the bigger cubes at lower rpm and increase longevity especially with boost.

Not to mention the torque that comes with bigger cubes!

If he goes with bigger cubes and the huge torque that they develop he can forget about Ever having a bravo drive last. I have had several big cube boats with bravos and that is why I do not have them anymore... Even a strong NA 540 in a 42 staggered will destroy bravo drives especially in big water .... Ask anyone that has owned a 42 with big power with bravo drives and they will enlighten you. After replacing them time and again they either got rid of the boat or went to a different drive. Bravo is a great drive to it's threshold which in my opinion is about 600HP. Once you cross that they will not hold up. Yes some do get away with it in light boats, but very few and changing gears all the time...
If you are going to build big power the first thing to do is the drives. Most everyone does it backwards by doing the engines first including myself until you have had enough drive trouble. A lot of time it will cause lost interest in the boat....

I guess someone should call mercury and tell them the 900 sc's should've been 632's instead of 540's...

540 = reason to love a 500 Bulldog :D

Ding ding ding!

This is the same conversation that I have with customers all the time. They want to build a 632 and put oval ports on it because "Cubic inches make power!".

Another thing to consider, fuel usage at idle, in no wake zones, and at cruise. The fewer cubic inches you have to feed at these times (90% of your boating time) leads to less money spent on gas at the pump. Make the best usage of the cubic inches you have by selecting heads with ports matched to your application (FI or NA), and efficient combustion chambers. A nice set of heads will cost about the same or less than a 502+ CI short block anyway.

This is what I'm doing with the LS twin turbo motors that I'm building. I am running turbos for the added performance benefits without the parasitic loss of blowers and a large bore motor. Consider how much HP it takes to spin a blower over the life of your motor, then relate that to gas you have to buy. Then consider if the HP that you are using to turn that windmill directly equates to a loss in potential speed. My little 370CI motors use 60% of the fuel at idle in gear that my old 525SC's used and less fuel at cruising RPM while making more torque and HP and top out at 900HP.

Efficiency will be the name of the game for the entry to mid level boater of the next generation.


EDIT: I'm not really trying to start a forced induction debate, just illistrating my point about using the cubic inches you have.

Higer rpm doesn't always mean more wear, if the internals are rated for it, I would rather spin at peak slightly unloaded then load it down to 5200 (which everyone thinks is the safe rpm). Full roller with his internals he will be safe at 5600 plus. I thought we were trying to save this guy money?

My dyno sheet on my blown 502ci may have you rethink that. Forced induction adds tons of torque, especially down low. Stop with the crazy talk

Please read this entire thread :

http://www.offshoreonly.com/forums/f...owerboats.html

If after reading that thread, you still want a faster boat.............sell the boat you have and buy a faster boat.

Ok. After all this reading. Sell what motors you have and order merc 1650s and 6s. That should get ya where ya wanna go. Lol. Boosted 454s will easily hit your target. Again drives would be the potential issue. I've been looking at 42s and already planning an scx upper/sc lower swap before I even consider more power.

I've been running my 468's, blown, for years now.

They made 800hp, 6 lbs of boost, non intercooled, ported dart heads, 420 B&M blowers, 850 holley carbs. Just this week logged over 200 miles on them at loto. They idle all day long too.

They made 730ft lbs across the rpm band give or take a few lbs. Sure would I rather have blown 540's, you bet. But I'd still take them over a pair of run of the mill NA 540's any day.

Cubic inches is nice but new blocks, stroker cranks , and all that adds up in money. For your hp goals, the 525sc can do it with better parts. IE bigger blower, dual carbs, the right roller cams, and so on.

I've been running my 468's, blown, for years now.

They made 800hp, 6 lbs of boost, non intercooled, ported dart heads, 420 B&M blowers, 850 holley carbs. Just this week logged over 200 miles on them at loto. They idle all day long too.

They made 730ft lbs across the rpm band give or take a few lbs. Sure would I rather have blown 540's, you bet. But I'd still take them over a pair of run of the mill NA 540's any day.

Cubic inches is nice but new blocks, stroker cranks , and all that adds up in money. For your hp goals, the 525sc can do it with better parts. IE bigger blower, dual carbs, the right roller cams, and so on.

Okay, what"s the dyno numbers on the roller 575s and how fast is Mild w the 800"s and does it still wamp on that cig. Heres the new nanny

Screw repowers. What's the displacement on those puppies!! I definitely see forced induction in her future!! Lol

With my current props, I can only turn them about 5500. My engines make 760hp at 5500. The boat will run about 90 in good conditions. My 38 fever has a few things going against it for speed though . No steps, ssm iv drives suck up some power. I would venture to say if I dropped my engines in a 2000 38 lightning , with bravos and shorties, it prob be a 100mph boat.

hry mild thunder can you give me a call or txt 850 585 4583 i have a question on the 420 blowers

That is probably true but with the ssm iv drives you are not setting dead in the water needing a tow home or limping in on one drive all the time. I would give up a few mph any day for the reliability of the bigger drives. It ruins you day quick with a broken boat....
I think many people wish they had SSM drives but it is a costly change from bravos. I think that is why they are trying Bmax.s and arneson drives.
If I was ordering another new boat and could either afford big engines or SSM drives it would for sure be the drives. It is easier to repower later with the SSM drives.. That way at least you will end up with a more reliable boat...
I know there has been untold amounts of money wasted trying to beef up the bravos with less than satisfying results...