I quick look at Mcmaster Carr only show steel for grade 8

this is interestin Arp does list there Sainless as having better properties then grade 8 by about 10%

http://www.arp-bolts.com/Tech/TechMetals.html

Quick Reference Guide to Fastener Materials
Material ARP Uses? Yield Strength Tensile Strength Used For
Grade 5 No 90,000 120,000 accessory bolts and studs
Grade 8 No 120,000 150,000 accessory bolts and studs
Stainless 300 Yes 140,000 170,000 accessory bolts & studs, head studs
Custom 450® Yes 150,000 180,000 head bolts, accessory bolts
8740 Chrome Moly Yes 160,000 190,000 rod bolts, head & main studs & bolts
A286 Yes 170,000 200,000 head bolts, accessory bolts
ARP2000 Yes 180,000 215-200,000 connecting rod bolts
L19 Yes 200-230,000 230-260,000 connecting rod bolts
Inconel 718 Yes 190-210,000 220-240,000 connecting rod bolts
Custom Age 625+ Yes 235-255,000 250-280,000 head studs, connecting rod bolts
ARP 3.5 Yes 220-250,000 250-280,000 connecting rod bolts
AerMet® 100 Yes 258,500 300,000 connecting rod bolts
Titanium Yes 160,000 180,000 head studs, accessory bolts

There are many grades of stainless. Get a very good grade of stainless and you'll be good to go. The best of both worlds, corrosion resist and strength.

from aquick search on stainless 300
PHYSICAL PROPERTIES(ANNEALED CONDITION)
Modulus of Elasticity in tension psi - 28.0 x 10(******)

so it looks like they could get some str=ong bolts out of it

never thought I'd have so many different opinions on that! I thought There was only one thing suggested / approved to go there!

Any boat manufacturer / racing shop on this board that has THE answer? What do you guys use in offshore racing?

Another thing everyone should be very concerned about is there are a lot of fake hardware manufacturers out there.
I'm in the military equipment business and virtually every fastener we use is grade 8. A number of years ago a lot of fake grade 8 stuff was being made in Taiwan.
ed

not sure on the thread size but assuming 1/2 inch the carbon steel grade 8 has a recommended torque of 119 ft lbs
http://www.engineershandbook.com/Tables/torque.htm

and from the Arp catalog look like they say there Stainles is good for 110 ft lbs you should be fine with the stainless just torque to spec and get the arps

Grade 8 only for motor mounts. I buy them from a local Fastenal store (Zinc-Chromate) plated to help with corrosion. This is the only way to go.

I recall that!
We had to do a stock sweep of all bolts. We ditched everything and reordered thousands of bolts.

Iggy,
We replaced every bolt on every M1 & M1A1 tank cannon in the fleet at contractor expense.
Funny thing happened afterwards. The USG decided to get rid of cadium plated hardware so we replaced them again.
ed