V6 lfx or lv3 for a boat

I build jet boats for fun and I would like some engine advice. I have installed and used sbc's, bbc's, (both tbi's and carb) and a Vw TDI in jet boats and have always wanted to use an ls someday. Now I have a project that could use 300hp and I have been looking at the lv3 and lfx.

My experience with efi has been limited to megasquirt and I would call myself barely competent with it. I bought hptuners and plan to fully dive into the modern gm engine world.

A little info about jet boats...the jet works like a water dyno. It can handle any amount of power depending on the impeller you put in. and the conditions don't change as far as it is concerned. Running full throttle tied to the dock or running at 60mph is effectively exactly the same as far as the requirements on the engine...it will take the same amount of power to turn the jet to 3000 rpm in both scenarios. Elevation will change and temperature...etc but the power requirements won't. Fully loaded and pulling a skier or empty the jet just shoots a certain amount of water out the back at a given rpm and it will always take the same amount of power to turn the jet at that rpm.

Also, all the engine needs to do is run so the computer has a relatively simple job. With all of the variables ecu's deal with I think the difficult part will be eliminating what the computer usually needs to see to run.

I like the lfx more because of the exhaust and cost but it seems like it requires more integration with the bcm and other systems which maybe harder to eliminate.

The lv3 also seems like an amazing engine but the ones I have found cost more and water jacketing the exhaust would be much more difficult. On the plus side it seems easier to work with the the computer and there is more after market support..

The questions I have are:

Has anyone set up a standalone (not even a transmission) lfx and how difficult was it? Where is there info about it?

What would you choose and why?

Where is more information about these engines and how they work?

I mostly want to get something running and reliable and I want to be able to learn as I do it. I don't want to just buy something plug and play I want to understand and be able to fiddle with it.

Thanks, Matt.

The power curves for those two engines are totally different. For your application I would think the LV3 would be more suitable. The LFX needs to run at 6800 RPM for peak power and 4800-5300 RPM for peak torque. Conversely, the LV3 peaks power comes in at 5300 RPM and peak torque is 3900 RPM. While a variant of the LFX was used in the mid size trucks, I'd say the LV3 is probably better designed for sustained operation at peak power given its usage in the full size truck.

Either can be made to run stand-alone with the same ease.

I think you are right. The larger engine has a better power curve for my application. I was just looking at peak power numbers and not really taking into account the shape of the curve. Adding a turbo would solve that but also add a significant amount of complexity that I don't think I am ready for. Do you know of a thread or site that can give me info about how to make the 4.3 standalone?

Thanks, Matt.

There are three supercharger options for the LFX, LGY and LGZ motors... I have the LGZ, which is the newest pick up version with a slightly different bore, different heads and cam..actually the block is a little different two. They also added some things like a stock, in valley oil evap can etc... The big difference is the intake manifold and down pipes (the collectors are cast in the head). All that being said, for a truck motor it is still real peaky.

Now those caddie versions of the motors. Twin turbo goodness... Little turbos too so some awesome low end power, forged everything... room for some serious power no matter how you want to make it.

I am not a boat lover and I’m not acknowledged in this field. As an engineer I can say that you’ll need engines with the same power curves. And as turnerpro said, the best option can be the lv3 because is more suitable in your case. If you are interested to make the 4.3 standalone, try to consult engineers that are specialized in boats and yachts. On internet I’m not sure that you’ll be able to find the necessary information you need. By the way have you ever tried to drive a yacht? I can recommend using miami boat rental, their services are of the highest quality. And there is a vast models of yachts that can be rented.