nopostduece

The boat was rigged with SBCs, it has twin disk tranys and kaama surface drives good for 1000HP. Getting the motors in the boat and making them run is not a problem. Should bolt right up to existing bellhousings and flex plates, motor plate the fronts and call it a day. However, getting the exhaust out of the boat is another story. The're wet manifolds on the market but are $1600 a pair, twice the cost of bone yard motors im out. I have thought of a few other options like sand rail headers, block huggers upside down or just make my own from a kit. The exhaust must be water injected at some point. all this trouble broadens the horizon...... Single turbo set ups on stock motors with valve springs???? Turbos and boats go hand and hand. See you have a good size radiator and constant cool water for liquid to air heat exchangers. But on the other hand the boat went 80MPH with mild 400HP SBCs so no need to get out of hand with the power. I think 550HP each would get it in the triple digits.

Any ideas on the best bang for the buck would be great. 6.0s vs 5.3s, convert to carbs with cams vs leaving stock injection with Ebay harnesses and cams, or going turbo... would it be cooler floatin' up with two Trexs choppin' with no muffs or hair dryers cryin. just looking for more thoughts on the project.

Now that im on the board someone put me in touch with Matt G. I worked with him at FASTech in Garland TX. about 10 years ago and lost touch, it would be good to here from him. Im sure he still posts here...

G-Body

iTrader: (4)

You could go 5.3 or 6.0. I would say if your going to go turbo use the 5.3`s. NA you will get more power out of the 6.0`s, but they are a little more expensive to buy.

The exhaust is a stumbling block, but I have heard that ford 351 cleavland exhaust manifolds have the same port spacing and some of the bolt holes even line up. So you should be able to find reasonably priced logs or even water injected headers.

Could go carb or injected, if going turbo definitely go injected. If not use whatever you are more comfortable with.

530sx

iTrader: (2)

sweet a thread involving my two favorite hobbies! this would be a great question for Speedwake or Offshoreonly. personally I'd rather have the dependability of an N/A setup with more low end grunt for hole shot. twin 6.0L would be awesome. the real cost though is going to be the rebuild on both motors. remember while boats just run older gen GM motors they are built completely different to allow for different tolerances...getting a 8000lb boat up on plane and then running it at 3500-6000rpm all day is a competely different job then driving a truck down the road and the motors are built differently to accomodate that sort of thing. I think it's a very challenging project. raw water pumps, exhaust manifolds and risers, oil coolers, fuel system, new cams, and then the whole fact that to my knowledge the only ls motors used in the marine industry are a few special edition inboard ski boats really adds to the difficulties.....sounds expensive (but isn't all boating). haha you could get brand new remanufactured marine SBC long blocks for around $1500 with some searching if you realy wanted....just some food for thought.

Ryphraph

iTrader: (2)

I would stick with the water cooled exhaust if the enginges are under a cover. The heat from dry headers can easily cause a fire. The only turbo boats out there are small, ski race boats that have the engine open to the air. Anything covered, use a supercharger.

Ryph

garys 68

iTrader: (1)

What he said.
Exhaust, 351 cleveland logs or these:
http://www.cassellmarine.com.au/p/85...manifolds.html
Spark arrested starters/alternators:
http://www.crusaderengines.com/Products/6_0.html

ace_xp2

IIRC somewhere on speedwake there's a thread about turbocharging. I believe someone there built watecooled shields to cover the turbine side,just an idea.

s.r.e.

Before you get ahead of yourself if you want triple digits your probably going to need at least 800hp a piece. I just guessing but you have a 80'ish boat and speed gages are prone to inaccuracies. Shot in the dark says that on radar your boat will run 58 to 62mph. Also don't think what works in a car applies to boats or your motors will have a life expectancy of twenty hours run time. Think truck towing a loaded car hauler up a never ending hill. Totally different duty cycles, second heat and fiberglass is a bad combo. Turbos can be done but you have to be ready to spend the money for the right parts. Go supercharger less of a hassle to package on the water.

Paul57

Boats love (& need!!!) TORQUE!!! Definitely go 6.0!!!
If you decide to use a turbo or supercharger go LQ4.
If you are staying NA then LQ9. It has about 10 more ft lbs and 20-ish more HP to start with because of the extra compression.

ramdaspadhye

iTrader: (3)

Hell, if you're gonna go turbo, a 5.3 will suit you fine. The output stock for stock of an LQ4 vs a 5.3 turbo is minimal for the usual cost difference in the motors (usually 500-1000 each). If you know you're going turbo, def go with the 5.3's. If you're going all motor, go with 6.0's, pref the LQ9 if you're gonna leave it stock.

garys 68

iTrader: (1)

BTW, I've been in a 31' Scarab at over 90mph, 540s, SSMIVs. The hull gets pretty unstable at that speed. Dont bother to build hp for those speeds.
As for turbos, they eat motors in boats. I cant think any non racing boat motor offered since about 1980. There are plenty of supercharged motors though. I've had Merc 525SCs, great motor, last a lot of hours, low CR, 5psi boost.
Check out these guys:
http://www.raylarengine.com/550_engine.html
Also check out GM:
http://www.gm.com/experience/technol...ne_engines.jsp

Ryphraph

iTrader: (2)

A boat's speed is often dependant on the hull. You could end up doubling the HP to only get about 5 more MPH in some cases. If you are running 80 with mild small blocks, you would be way ahead just to freshen them and have a good running boat. Twins suck for maintenance as the cost of everything is doubled and there is little room to work. a FI system will add to these issues. A higher performance set up will take more fun out of your boating experience in the long run in my opinion. I have always had mor fun on solid stock boats than high performance set ups but that is just me.

Ryph

GIGAPUNK

iTrader: (2)

turbo 5.3s will hit 500 for sure. Why not just use stock, cast, truck manifolds. Then have them and the turbine ceramic coated and inject the water after the turbo. Add a little ventilation to the engine compartment and you're good. For the cost that turbos add though, you may find it just as cost effective to build a n/a LQ9 block with stock L92 heads. That will get you over 500 hp as well, be easier to tune, weigh less, and not run as hot.

nopostduece

well i have the exhaust problem solved. Schoenfeld Headers has sprint car/dyno headers for $279. should work with minimal modds. tig in some bungs for water injection an inch after the flange and get them coated in and out. i think im just going to stick stock 6.0 bone yard dogs with cams for this season. beat the hell out of them, and if they live freshen up the bottom ends and go with l92 heads over next winter. the boat is not a production piece, its an old race boat with surface drives and very well built. i have had a few "marine motors" apart and never found anything more then rotators on the IN/EX valves, and mild cam (witch got trashed for better parts in the builds) compared to an auto motor.

i think i can pull it off under 6k.

s.r.e.

Its not water injection on boat headers. The headers are actually a double walled to create a water jacket. Water doesn't actually enter the exhaust until just before the transom. Doing what your thinking is just asking for trouble. I've been doing the go fast thing on the water for twenty years now. We had 20k into a 454 stroked to a 498 with World block and heads. It pulls 650hp on the dyno and still need a to be freshened up every 350 hours. Its was built and gets refreshed by the same shop that use to build the motors for the USA1 monster truck. If your going to go down this road your really going to want to go talk to someone that knows marine motors.

G-Body

iTrader: (4)

Some boat headers are water injected not water jacketed. They are typically only used on smaller ( <25 foot) jets and v-drives though.

If you are going to run injected headers you should be running a banderlog valve or something similar to cut down on the chances of reversion

s.r.e.

OK thats a new one. I've seen some peoples crazy redneck stuff, but I've never seen anyone nutter enough to run a setup like that.

G-Body

iTrader: (4)

Thats very common practice on jet boats. Never really seen it on the big offshore boats, but the california style performance boats have been doing it since at least the 70`s. http://www.bassettracing.com/faq1.htm Bassett headers are the first large company that makes water injected headers that comes to mind, but I know there are others. But then again this is also popular on boats that don`t have much of an option to run a water cooled log manifold anyway because the boat is 12-18 inches tall from the bottom of the keel to the top of the transom. They almost have to run over the transom headers.

hotrodscrap

iTrader: (10)

Want to see some pic's, gl on your LS boat!

-SS