I want to upgrade my engines and was wondering how much hp I can get without crossing the realiable border? also roughly what would I be looking at in cost to build?

prepropower.com has 377 scorpions for 10k... ted

With GOOD parts (rods, pistons, bearings, lifters, crank, roller rockers, etc....) and some head work you should be able to get 400+ pretty easy without making anchors out of them. Bear in mind, compression builds HP, and needs higher octane fuel. If you fuel on the water often, this can be an issue in many places. Which is why I stayed below 9:1 on my BBC.

If you can do the dissassembly and re-assembly yourself, you should be able to do it for $2000 each or so. If you have it done, You're looking at $5000 plus each. Crazyhorse and I did all the wrenching on mine. Parts and machine work set me back about $1200 or so. We did re-use some of my parts though. Rocker arms, push rods, heads. Then again, I may be all wet with my estimate as I have been doing it myself for years now. Last motor I had "tuned up" cost me about $3000 and lasted about 30 hours before it ate itself.

To see 400 in a sbc your pretty well into a cyl head change if you dont want to use too much compression to make power and you'll probably have to spin it to 5200 rpm or higher......thats for a 350, a 383 is a different story, but if your going for the extra $ to make a 383 you might as well go a few extra hundred bucks more and make a 406.......Ive been all over this lately , I have two 350s in the back of my 29, Make a stout 383 or 406 and you'll have to be careful with the alpha you probably have hooked to that 350..........Doug

...I looked at all my options. 383 kits are so cheap now, that it was cheaper to buy a race-prepped 383 short block, than do the machine work to bring my old 350 back to life with a new set of pistons. If you go with the stroker, the extra cubes will help reliability (can run less compression and cam).

I squeezed over 450 HP (at 5,200 RPMs) and over 460 ft-lbs (at 3,000 RPMs) out of my semi-mild 383 for under $7K. This included Edelbrock aluminum heads, Crane hydraulic roller cam, TRW forged slugs, and SCAT crank. Idles around 900-1,000RPMs, and has gobs of torque (did I just say "gobs"?) very early in the power band.

Like twinn29 pointed out, you can go 406, but there are clearances to address.

Phaff sells these 383 motors for around $10K, but he uses the Brodix heads, and makes a little more HP a little higher in the power band (around 5,800 RPMs).

SBC parts are very cheap. Reliable? I would say 380-400 reliable HP is a piece of cake...

OK thanks guys now my question is what kind of speed increase can I expect with another 200hp on a on a 5000lb. 28ft. vee hull?

I've always used the 1 hp/1 cid as a rule of thumb for reliable. Anything above that is getting more in the radical side. As far as speed increase, I went from 200 to 330 hp in a 3100# 20 footer and only saw an 8 mph increase. That is a 65% increase of power for for a 21% increase of speed. I was hoping for more.

I've been looking into 383" engines and ran across an article in Chevy High Performance magazine. They were working on a 383 GM crate motor. They swapped the factory cam for a GM Performance parts cam, swapped the rockers to roller type 1.6:1 and topped it with an Edelbrock RPM Air Gap and a Holley 750. This combo pumped out 446 HP@5400 and 473 lbs. torque@4400 on 9:1 cmpression.

The cost of all this was:

Engine 3699.00
Rockers 301.00
Intake 210.00
Cam 193.00
Carb 430.00

Total cost 4833.00 +/-

Sounds like a good deal to me.
I see no reason this wouldn't work in a marine environment.

A friend of mine has some 350's that are pretty indestructable.

Stock (2 bolt)
Stock crank
Lunati rods
JE pistons.
Canfield aluminum heads (10:1)
Solid roller cams
I don't remember what intakes.

Well he spins these motors 6000 , they pushed a 85 Wellcraft Nova to a best of 74 on GPS.
He just went thru them (350hrs ) and everything looked good except some of the Crane roller rockers were worn.
He now has those same motors in a 96 31 Scarab. They were out testing Sunday with it and with 5 people it went 71 on the Nordskog speedo.
I would say those motors are making around 425 a piece and they are pretty reliable.

I built a 383 over the winter...

4 bolt block ( w/ clearancing)
eagle forged crank
eagle forged H beam 6.00" rods
SRP 9.8:1 forged pistons ( dished)
vortec cast iron heads ( w/ screw in studs, guidplates, guidplates, and pushrods holes clearanced)
edelbrock RPM air gap intake
crane roller cam...
1.6 roller rockers
750 holley

I am guessing around 400-410 hp...

The stock 350 mag spun a 21" pitch at 4500 rpm now the new 383 spins a 25" around 5200

Its about the same motor as Iggy is talking about in the chevy high performance magazine

I have run the dog **** outta this thing for 35 hrs now.... found a broke piston at 20 hrs.. fixed that and have had no other problems..

Travis