Does anyone know what the hp/tq and rpm limits of the Penta SX-A 1.51 outdrive are? The boat is a 2008 Four Winns H220 SS with the Volvo 5.7 gxi and it weighs roughly 4300#.

I would like to build a 383/406 sbc or possibly an LS3 to replace the gxi but I would really like to know what the outdrive can handle before deciding. I've done some searching and only found a couple discussions on the SX-A, unfortunately the results were conflicting. One said this outdrive is very stout in stock form and the other stated it can't handle much more than the factory power output. Any information would be great!

Don't know the answer to that but maybe BUP will see this and chime in. He's also up on all things Volvo.
One thing that I find interesting is that for the 496s Volvo only uses the DPS/a unit , not the single prop SX/a and there can't be a huge difference in the internal parts limits, surely ?

new SX came out for model year 2008 and it is a bit faster thru the water than the SX version before it. The neg is its cases are tad thinner so HP levels are not as big. Anyways Volvo themselves never put the single prop SX on anything bigger than 400 hp. They used the DP outdrive for anything 415 hp and above. the 496 HP MAG had a DP outdrive but you could get the 496 mag with either outdrive.

Volvo does not use big blocks anymore since model year 2012.

here is the newer SX 2008 to current SX
drive

so to answer the question correctly Volvo did not use the sx for anything 415 hp and above they used the SX for all below 415 hp. So with that said there is a reason for it. They did not want it to be said their drives could not hold up per their engines. Also IMO the break away coupler is the real reason for not adapting big power to the drive from Volvo. They have a small spline break away shaft for impact damage to save the drive for a short jist

old SX just before the 2008 version - this version is stronger but slower thru the water 1 to 3 mph depending

BUP , does the DPS/a unit not have a breakaway coupler ?

Well, that's not the news I was looking for lol. I was really hoping to hear they could handle close to 500hp. I'm not really looking to go all that much faster, since I doubt the hull is really suited for much more than low 60's My hope was just to build a mild LS3, with 10:1 and a decent sized cam. More for just having it sound more nasty than it is. I dont know anything about outdrives so I have no idea what the weak points are and how to strengthen them.

The more I research this project the deeper it gets. My boat has captains call with the exhaust out the sides and it sits pretty low in the water. So I'm sure that will not be good for water reversion. Not sure if this project is worth the trouble.