I have a 29ft envision engine is a dog. I know 496 ho and 502mag are good options but can't seem to find any. I'm in missouri. Drive is a bravo 1 so wanting to stay around 550hp. I have a 454 in the garage thats a 2 piece rear main. Not a boat engine builder but if I had all the pieces I could build the engine. What's the best thing or option to upgrade my engine. I know l29 is all hyper internals and cast crank not good for a build. Will my 2 piece block be usable for a build? Just bare block? I know nothing about marine stuff. Any helps appreciated

Keep in mind that hull is a dog as well. Great rough water hull but takes a million HP to get any speed out of it. What are your goals with the engine swap?

I'm out on lake ozark speed is not my concern as much as big water and it being smooth. I just want the punch of a high compression engine. Tops at 46mph rite now. It has a 454 mpi and it sound pitiful

Reasonably priced higher hp engines are few and far between; I myself have been looking for a nice 500EFI to swap for my 454 MPI. It comes down to are you willing to drop maybe 30 large to get...8 - 10 mph more? I boat on Table Rock pretty much exclusively and it has become rougher and rougher over the last few years, to the point that a 35 - 40 mph cruise in the rough stuff is about all I really want to do these days. And LOTO is far, far rougher...on a good day, in any of the 'big water' areas. I get where you are coming from, speed is fun, my last boat was a high 60s/low 70s boat...and I miss that, but there were very few places on TR that I could open it up and run that. It sounds like you boat handles the rough stuff nicely. You have two engines that are suited for different levels of power increase, or you can go to a blue engine and scratch that speed itch a bit, lol!

Roll and stroke the 454 and make a 496 out of it. More than likely it's a 4 bolt already.

The MPI came out in in '96. It's a 4 bolt main. All 454's from about 91-92 (Gen V) are standard 4 bolt mains.
It would be an easy build to do and a lot cheaper than buying a complete motor. Wouldn't even have to bore it if all you want is around 550hp.

As an alternative to strokin it, I picked up 10 mph in a 24x7 by doing the following:
Cam: I used a Crane 169611, required cutting some notches in the pistons, and cutting the valve guides down for seals for dual springs and to clear the bottom of the valve retainer.
Intake: any single plane, I used a Vic Jr.
Heads: Stock, just smoothed the intake ports out out with a burr, and slightly reshaped the exhaust.
EMI thunder exhaust.
I used a 0.027" head gasket, the chambers in the L29 heads are already 100CC so it put me barely over 9:1.
All pretty DIY, no need to take it to a machine shop, I didn't even touch the bottom end, have about ~200 hours on it with no problems yet.

That crane cam is what merc used in it’s HP500’s.