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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.

Quote:

Originally Posted by BLUEMAGIC (Post 4162895)

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.

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

Quote:

Originally Posted by 682gold (Post 4162784)

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.

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.

Quote:

Originally Posted by RaggedEdge (Post 4163328)

Yeah! :)

Quote:

Originally Posted by 682gold (Post 4162784)

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

Quote:

Originally Posted by 4bus (Post 4163281)

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.

Quote:

Originally Posted by mcprodesign (Post 4163392)

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..

Quote:

Originally Posted by 682gold (Post 4163463)

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

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.