Indmar's website states Premium recommended but not required for the LS3. I have recently put a good bit of time on an LS3 and put mid grade in it as I have with my other boats. It really is a strong motor. I like it. I have the 340hp 5.7 in my boat and a friend has the 6.0 409hp in his. The LS3 450hp clearly is much stronger than the 409. A larger jump on performance than between the 5.7 and the 6.0. I have some time in 2 of the SA boats as well. Very nice handling boat, great wake. You will enjoy it.
I've built, tuned and ran the crap out of the 5.7, 6.0 and 6.2, in various cars and boats. FWIW I have the 5.7 in my boat. The 6.0 and 6.2 are really sensitive to octane and should be ran on premium. Ran on low or mid-grade you will almost certainly get pinging under load which will result in the ECU REALLY backing down the timing and killing your power. The 5.7 is somewhat more forgiving, since typically the compression ratio is not as high and the boat cams are somewhat tame.
Also Kevin I dont understand your comment on the 6.2 >> 6.0 > 5.7. The diff between the 6.0 and 5.7 is larger, and also it's a more noticeable torque difference than the 6.0 -> 6.2 ??
On similar boats, specifically 24 ft boats, one with 5.7, one with 6.0 and one with 6.2, all at roughly the same test weight, each with stock prop, the 6.2 gave the shortest time to plane. The gap between the 5.7-6.0 time to plane was less than that of the 6.0-6.2 time. On a smaller boat on other test condition, the results may vary. The 6.2 seems to pull and get to plane more closely to the LSA supercharged 6.2 than the 6.0 L96. The seat of the pants grunt of the LS3 is impressive. My boat is the one with the 5.7 in it and my buddies are sure to let me know from time to time...
Hmm, ok thanks for the info. I'm in a 23ft and I've seen a bigger difference with props than motors, in general, with similiar boats, but there's no doubt that the LS3 is a healthy motor. Speaking from my car experience, the main appreciable difference is in the L92 heads. Swap them onto the 6.0 and they're terrifically close in power output.
I could stand to have another 50hp when heavily loaded (>3k lbs), but >400hp just seems not nessecary to me, in a wake boat. Is it just a peen thing, or is there a practical use for the extra uumpf, besides burning fuel?
These motors are designed to run on premium. The funny thing is with the timing pulled, you will make less power and end up consuming more fuel - in the end costing yourself more money in fuel than just buying premium. Premium tends to be only $.20/gallon more than regular. With regular averaging say $3.50/gallon, it's only a 5.7% increase in cost at the pump with that percentage going down when fuel costs go up.