Hey guys,

Longtime lurker but finally decided to join. I am looking to either upgrade my motor or eventually repower. I have two Chaparral 2550 SXs, one fully restored/upgraded aka mint and one 7/10. I love this boat and it is seaworthy and suitable for big water, while being single-engined and trailerable by my SUV. It really ticks all of my boxes and is likely a boat ill keep for many more years as sport cuddies have gone out of style.

I would like more speed and performance within reason. The hull is 20 degrees with a pad. The boat weighs about 5,000 lbs. I like the Bravo 3 for overall efficiency, docking, fast planing, rough water performance, etc. My current cruise speed is a respectable 35-40 MPH GPS and top speed is around 52 MPH GPS. I would like to get close to, or break, 60. I would like to cruise 45 without stressing the motor. I think these goals are realistic. I am torn between old and new school. I did a top end rebuild on my motor in 2020 and its been bulletproof since. If money were no object, I would sell my 454 and drop one of these in:

*6.2 L87 EnPac by Marine Power (Full closed cooling, no cats)

Does anybody have experience with this Marine Power offering? There is also this one by Kodiak, but it has exhaust catalysts so I'm leery.



I could also possibly build my own or have one built if anyone has any recommendations in that regard. I am a fairly experienced mechanic, but am out of my depth with this new school stuff.

Thoughts? I have no interest in getting rid of my boat for something like a go-fast as they aren't versatile or functional enough for diving, overnighting, etc.

I would post links and pictures, but it won't let me.

The direct injection system as far as I know...has the issue of the back of intake valves getting carboned up from not having fuel wash and clean etc...as well as egr.

Many LS options for marine, to utilize the good heads and cam base circle size, without going DI.

I like the L8T block, as it has longer cyl bores and allows longer strokes without the piston skirts coming out at the bottom. But I would not use the DI heads and system.

I like to minimize complicated systems in marine systems as much as I can. DI and variable cam phasing type tech seems to be more complicated than it's worth.

the load in a boat application is probably high enough for that to never be an issue

Yeah I know DI can carbon up valves, but I would think the fuel metering and delivery would be advanced enough by this point to keep things running smoothly for the long run.

How difficult would you say it is to build an LS from an auto engine that's been pulled out? If I could find a suitable core and off the shelf parts to convert it I would consider that route, but nothing is as reliable as a complete finished product like the Marine Power LT motor.

Here's my boat by the way, at this point it is all theoretical as the 454 runs like a top.

If you search there are threads such as yours that pop up every 6 or so months.
I know you're window shopping.
But that offering from marine power is rated at 420HP.
If you want to say you got an LT DI in your boat fine.

But you could out-do that power with a good build on your 454.
Supercharge a good build on your 454 and you'll clobber it!
With more torque everywhere with both builds.

Money no object, might as well spring for Marine Power LT4 offering from their Sportpac line.

To answer your DI in boats question, it's been going on.
Probably overwhelmingly as those wake boats are all you see anymore on most inland lakes/rivers.
Be nice to see the last few years production figures on them.
I don't know when they started but the brands below are all pretty much GM DI.
Malibu is using their in house produced marinized GM DI 5.3, 6.2, and the LT4 in their boats now.
PCM offers GM DI 5.3 and 6.2 for Natique and the 6.2 for Centurion boats.
Ilmor is also doing DI 5.3, 6.2, and the LT4 for Mastercraft.

I've always been about losing weight etc...but the iron LS blocks are only a few pounds less than a BBC block.

Alum heads on a BBC with a well designed package is hard to beat.

BBCs are very responsive to getting more power out of them. You are better starting with a good solid foundation of the bottom end.

Then don't complicate things. That 454 has plenty of upgrade options that you could wrench yourself. A new mil transplant is far from plug an play. Everything from a new fuel system, wiring, gauges, controls. motor mounts, alignment, just to name a few.

No replacement for displacement!

What year are they? My wife and I had the exact boat however ours was a 1988 2550 SX with a stock 454. I installed lightning headers and cut in through hull exhaust. Ours had a B1 and It would run 60 mph (not gps) We would probably still have it today if we didn't lose it in a storage fire.