ttpower

I currently have the stock merc 330's and the boat tops out at approx 4600rpm and 65mph with 25p mirages. From what I've read, these motors make approx. 460ftlb and to my knowlege that's the most important thing in a boat. A stump puller.
Now, I have been searching ALOT on lq4/9's and people putting them in jetboats. That info has been helpful, but still leaves unanswered questions.
Its evident with stock gm part swaps from the lsx family, you can make gobs of power with these platforms. Thats fantastic, except for the rpms required to do so. From a marine aspect that's not good.
Has anyone ever engine dyno'd an lq4/9 combo? rwhp #'s need not apply. I know the stock lq4 is rated @ 300/360tq and the lq9 345/380tq. Is it possible to make the required tq to get my pig on plane and satisfy the rpm window of TYPICAL marine engines? I figured a max of 5000-5250rpm is ok. I started the thread saying lq4 because of the lower compression, and I predominantly run regular.
I know I COULD drop pitch and make up for the tq difference with prop rpm, but that's not appealing to me. Cruise speed and range would drop.
This swap should make the boat faster, well more efficient, if it produces the same hp/tq as my stock junkers. Id be saving 500lbs., probably more. The boat looses approx 3-4mph stuffed with 150gal of fuel. I know it doesnt sound like much, but that's a HUGE difference when it comes to boats.
As far as the swap goes, Ill be using oem PCM manifolds and modifying the flexplate to accept the coupler. Bell should bolt up (minus a bolt from what I've read). I can fab the mounts. Psi harness. DIY Closed cooling.

71ANTICARB

iTrader: (23)

A boat is sooo not what I was thinkin when I read the title. Sorry no help though.

Pocket

iTrader: (22)

Put an overdriven large displacement roots or twin screw on top of them and a decent blower cam in the middle

Hope you've got deep pockets though

ttpower

lol that'd be insane

squee

iTrader: (16)

Kenne Bell twin screw can make **** LOADS of torque down low and some SERIOUS horsepower. LQ4 would be the better choice for superchargers as well, obviously.

ttpower

I would never do such a horrid thing to a beautiful motor when god gave us turbos to play with

Deep pockets? Thanks a negative ghost rider, but I have the stupidity and tools to fabricate just about anything. LOL I can get 2 lq4's for ~800 a piece, rebuild kits are <600, rod bolts <200, the manifolds are under 200 each, risers ~ 150ea, SS 800k btu heat exchangers~ 300 each, harnesses are no problem, fuel pump's no problem, engine swap/upgrades say 750 each, and tuning is free. Yea, that's scary.. but I have 2 motors that will sell for 2500 each in a heartbeat.

ttpower

turbo's make even more, more efficiently

ttpower

anyone can make tq with boost, I have a turbo car Thats not the point of the thread..... lq4/9 ........... stump puller......... go...

Pocket

iTrader: (22)

The point of a roots/twin screw SC engine is to make instant torque from the rock bottom to mid range with a very flat torque curve which is where you wanted your boat to be

sierrac3_s2000

iTrader: (6)

You might want to look at the LY6 engine. Its a 6.0 but with the L92 heads and has VVT which gives you more low end torque. With a CAM and valve spring swap and tune you can have almost 500 lb/ft of torque and its going to be a very flat curve. My L92 with Mast Motorsports CAM makes right at 400 lb/ft of torque at 2000 rpm.

ttpower

now that sounds promising

Irish350

iTrader: (14)

good point about the ly6, but that might not be cost effective. Especially if you're a turbo/fab guy, why not grab a couple lq4s and a couple turbos and entertain us all?



but really, i wonder what one of the 'cam gurus' would say about factory lq4 heads and a "marine torque cam" (say pat g, ed c@ flowtech, etc) and stock cubes.

I dont know **** about any of these boat builds but theyre probably one of my favorite things to follow

ttpower

cost effectiveness is key and that's why Id love to do this. IF they can make the same pwer, they are more efficient, and the pwr/weight ratio is better. All around the boat should perform better.

I was just going to toss some internally gated turbo's on my 330's, but IMO it be a waste except for the wow factor. Would it work, absolutely.. would I shatter the shorts, absolutely lol

The ONLY thing I dont like about using a power adder is that you WILL burn a **** load more fuel...

here here to the cam guru's!!

BLINGOLE

iTrader: (5)

Whatever route you go just make sure you retain the big truck intake manifolds. Those are a big part of the low end torque.

BLINGOLE

iTrader: (5)

Hell I wonder if you scratched those 317 70cc heads for some 241 heads or something while your rebuilding these. I mean a strong comp ratio should bringmidrange torque up and the cam profile will determined your rpm range. I think. Just a idea some heads like 241,799 etc etc can almost get giving to u at times.

Lq4's seem to make great midrange power to,, obvisouly drive a 2005 2500. So the cams may be ok ifyour on a budget

ttpower

The manifolds must be water jacketed because its an enclosed engine compartment. The main thing is getting it on plane.. Currently with the fat a$$es, it will get on plane @ ~2500 with proper use of the kplanes.



I am not partial to any motor/combination right now, just as long as I can run regular/plus. The cam might work.. water reversion might be an issue tho. Hell, I tow the some beotch with my tbss. I only run regular in that and there is no detonation(as far and the knock sensors say). Its even leaned out a bit lol

LQ9CHEVELLE

iTrader: (2)

Those mercruiser 330hp 454 motors were pretty anemic. Mercury sells a 377 scorpion small block, and a 383 (remanufactured) smallblock that is advertised as a good replacement for old, tired 330hp 454 motors. Many people have used them and picked up 3-5 mph with the added HP and less weight, despite the drop in torque. Also, i would doubt that a stock 330hp mercruiser actually makes 460lb ft of torque, at least @ rpm where the motor actually needs it (@ cruise rpm....the torque does no good if it peaks @ 2000k, that part of the power band is hardly used). I think a LQ4 or LQ9 repower would be very successful. You would be shaving 400lbs or more of the back of the boat, and gaining horsepower. I was researching this for my old boat, and was about to pull the trigger on the project, untill I came across my current boat

LQ9CHEVELLE

iTrader: (2)

Stock LQ4 camshaft in later model motors are wider than 115lsa, that is very safe, no need to worry about water reversion back into the cylinders. The water jacketed exhaust manifolds are available from a austrailian company for a reasonable price. Indmar uses these motors, stock GM cam and all, in their "LQ9" engine packages, commonly found in wakeboard boats. They won't sell thier exhaust risers and manifolds seperately though, I checked