FormulaZR

iTrader: (7)

Ok guys - here's the deal. I have a 21' tunnel hull cat jet boat; and right now it has a 383 LS1 in it. Currently it's making about 525 fwhp (observed) @ 5800-6000 rpm.

I am looking to step up to something more along the lines of 850+ fwhp @ 5500-6100 rpm. I'm currently between several options. However, it's not simply as easy as you would think. Boats, unlike cars operate under a different set of circumstances - in my case it's mostly constant load (from the jet pump) and sustained (5-10 minute) high rpm.

I'm not really wanting to go an iron block because the boat really seems to like the weight savings of the aluminum engine.

So - here's my dilemma; do I:
1) Stay with the 383 - lower compression and FI it?
2) Go with an LS2 at 402-416 CI and FI it?
3) Go with an ERL Dry Sleeve with more CI and FI?
4) Go with an ERL Superdeck 1 with more CI and FI?
5) Reluctantly go with an iron 408 with FI?
6) Even more reluctantly go with an LSX with FI?
7) Something I haven't thought of yet?
8) *Maybe* try to figure out some way to go with an LS9?

I don't have unlimited funds - but I don't want a ticking time bomb either.

I'd like to stay with LS1/LS6 type ports and use the Fast 102 LSX RT intake - but if I need to change, I will. I'd think it's important to keep bore/stroke in mind when it comes to reliability...

EDIT: Talked to Virginia Speed, and this is the route I will be going. Looks like an RHS tall deck is in my future! Those guys over there sure know their stuff when it comes to marine engines...

PowerShift408

iTrader: (44)

I don't see a reason why you should compromise, stick with the aluminum block like you want. Seeing the circumstances that your boat is subjected to, that seems comparable to a road racing motor build. And when I think of LSx series motors and road racing, Katech comes to mind. I would recommend getting in touch with them and have them give you some thoughts on the project.

FormulaZR

iTrader: (7)

Yes - I'd agree...very similar to a road race/NASCAR type deal...

I have contacted Katech - and I'm on a little smaller budget...

PowerShift408

iTrader: (44)

Wow, didn't really expect that. Well in that case, give LME a shot. They just completed a pretty big build with me. Their customer service is nothing short of excellent and they will do whatever it takes to make sure that you're happy with the product. Bryan is great to talk to on the phone as well. He helped me out a lot, being that I'm currently in Iraq and my motor got finished since I've been here. Tell him Alex sent you his way. Their number is 1(713)849-4505.

redtan

iTrader: (5)

You can easily make the power that you want with some boost on the current engine you have. If there's nothing wrong with it and if it's build right, then there's no reason to have to change it. Like you said, lower the compression and throw some boost at it...that should work fine.

If you had the money sure go ahead and build a whole new engine+fi, but you said funds are limited so just use the already solid setup you have now and improve on it by boosting it. A forged rotating assembly should last quite a while under fi and sustained load.

farmington

iTrader: (14)

That thing is crying out for a turbo. With an air to water intercooler you could run pretty decent boost on pump gas too.

CHADsterss

mpatton

Besides all that ^^^^i would just go forced induction. Lower your compression etc and your goal is easily doable

FormulaZR

iTrader: (7)

Yes, I agree - I am trying to piece a twin turbo system together now.

I am still undecided on lowering my CR and seeing how the 383 performs - or going with a different setup.

pairof69s

Rectangular port heads and TURBO.........Wooooo!

COPO9560

I agree with others that FI is your best approach. You simply won't get 850 hp at the rpm levels you are looking for with the LS platform. 850 hp in NA form is easier to obtain from a BBC - at a lower cost but significant weight gain.

I'd suggest you consider going to an iron block 370 or 408 and reusing your top end. The larger bore will help the heads breath a little better and the iron block is more durable when producing 800 hp for more than 10 seconds at a time. You don't need a huge engine with FI - save your money and invest in quality rotating parts.

Turbo would be ideal for a jet boat but Procharger is a much easier install. The exhaust systems on boats are very expensive - you get to keep yours if you use a supercharger, with turbo it is all going up for sale.

Lastly - very important for FI boat is to use inconel exhaust valves. Stainless will not take the long term heat that a FI boat engine produces.

FormulaZR

iTrader: (7)

Spend quite a bit of time on the phone with Shawn at Virginia Speed - I gotta say, I'm impressed! Lots of knowledge about marine engines in general (coupled with what we already knew about them).

Anyway, looks like a tall deck RHS block is in my future. I have to collect some more funds; but when I do stay tuned for the build.