ls swap a boat
 

just got a new boat it has 2 inboards and 2 alpha 1 outdrives and looking at ls swapping it looking for any info on how to do it

you can look here: starts about the 3min mark

LS swap the world
 

Needs a turbo. I’ve been wondering about an LS swap, a 6.0 with a cam should put a beat down on an 454.

The LS is a great engine, but it needs a transmission with at least 1,8:1, preferably 2:1.
Our LS376/480 was lousy with the 1,56:1 transmission as the propeller spins to almost 4,000 rpm and lacks torque, but with the 2:1 transmission it's a completely different story. I wouldn't put it in the boat without at least a 1.8:1 gear option.

I take you have the motor in a inboard ski boat?

No, it is installed in a 4,900 lbs speedboat with MSA surface drive. With the ZF63A-1.56, the engine struggled to turn the SL5-22" propeller and would not go over 62 mph-Livorsi GPS. After swapping out the ZF63A-1.56 for the ZF63A-2.04, the engine spins Maximus 30" easily and we've gotten to 65 mph so far. It would go far over, but to small skeg made dangerous ride. We are prolonged skeg and on the spring will go back on the water. My expectations are betwen 67 and 70 mph, hopefully close to the 70 mph.

With transmision 1.56:

https://i.postimg.cc/RWZ07tpC/kajak.jpg

I have swapped a forged 370ci in a 94 baja outlaw. Message me if you have any questions.
https://cimg6.ibsrv.net/gimg/www.off...0dc665c740.jpg

A prop change can solve that pretty quick, but I realize that surface props are not the cheapest to source.

My Arnesons are 1.32, with cupped 25 pitch 5 blades. I don't think I would even try to turn them with SBCs or LSs. It does keep the cruise rpm down though...

Nice clean setup.

Care to share some horsepower and speed information?

And I would never put a bb mastodon in my speedboat. (I do not looking for 80+ Mph) This about the torques, the size of the boat and the inadequacy of the LS motor is often taken out of context on this forum. (Outboards with 400 or 500 hp do not have better torque than LS engines, all of rhem are surfacing "engines"...)

1.) I believe LS engines don't work well with Z drives because all decent Z drives have the biggest gear ratio of 1.6:1, which is too low for an LS that revs to 6,400 rpm and put out the best power at 5,800 to 6,200 rpm. In this case, you get about 4,000 rpm on the propeller, which means very little torque and this is only suitable for very light and fast speedboats, with less than 3.500 lbs weight for each engine.
2.) If you put a 2:1 gear between the LS engine and the propeller, you get, in my case with the LS376/480, torques on the propeller that are very comparable to the torques of the Merc. 525 EFI and 1.5:1 gear drive.
3.) Check out the Volvo Penta inboard motors for example!
4.) LS engine and 2:1 transmision give similary prop rpm like BB with 1.6:1 transmision.

Our speedboat pulled like a snot with the 1.56:1 gear. It took 7 seconds to come out of the water and 12 seconds to 20 Mph, but when we put in the 2:1 gearbox and the Maximus 30, it reaches 20 Mph in about 6 seconds and up to 65 Mph the first results are very comparable to the Velocity SC29 test with 8.1 HO, which seems ok to me for the first tests. I guess we will need a 28" propeller in the end.

A very simple calc that is good enough for comparison is:
P = D**** x n*** x H** x A
P = needed power to turn prop. In this case only like factor to compare diferent situations.
D = propeller diameter
n = propeller rpm
H = propeller pitch
A = propeller area
told me that with a Signature LS 22 propeller and a 1.56 gear, I put out 485 hp, and the same work was done that would have been done at the same speed achieved with a 2:1 gear, a 30" propeller, and 375 hp!
Due to the simplification of the formula, you do not get an exact power result, but it is enough to compare different situations.

Not to go too far, I would like to share my next opinion:
If you have the possibility of using a gear ratio of at least 1.8:1, even better 2:1, the LS engine is at least as good as the BB with much lower consumption. With Z drives you must have less than 3.500 lbs boat weight per engine.


p.s.
I hope the text is understandable, I didn't mix up the words too much and at the same time I apologize for my English.

Throw a lot of extra money at it and hope it performs.

The alpha drive has a 2:1 gear ratio.

What Alpha drive are you referring to? He never listed a serial #.
The have:
1.47
1.62
1.81
1.94
2.00
2.40

With 2:1 you will have better torque on the propeller than 8.2 HO with 1.6:1 and maximum propeller revolutions around 3,000 rpm.
With 1.94:1 you will have identical conditions on the propeller as with 8.2 HO and gear 1.6:1.
With 1.8:1 you will have similar conditions as with 8.2 HO and gear 1.5:1.
In all cases will be consumption of LS smaller becouse of better engine construction than BB and SB.
I do not know what will be the best for you, but I would looking betwen 1.94 ansd 2:1.

Depending on the weight of your vessel, search between these gears. Less mass comes on one motor with a smaller gear. I don't know how much the Alpha drive can handle, and with 1.8:1 it holds more than with 2:1.
About how much would your speedboat weigh? Check this: https://i.postimg.cc/jjTkKhHP/47713064-3.png it is just marine dresed LS3 or LT engine coupeled on Z drive.

You have to put aluminum exhausts on the engines because of the electrolysis (We put Kodiak.), which is the biggest additional cost. It will definitely be much lighter than SB.

Like I told: We have 4950 lbs heavy boat 30# LOA and id ride well with 2:1, MSA surface drive (Ugly but good except skeg which we need to prolongate.) MSA Marine Systems and at the moment Maximus 30, probably will be at the end 28, but I do not know yet.

You guys know how much power and load a 2:1 Alpha dive will handle ?
This is what the OP has

Back in the day I replaced a broken 1.47 that was behind my stock 260 with a 1.81 from a 4 cylinder that was laying around. Increased the pitch to get some of the speed back. The outdrive lasted a month before it broke the vertical shaft but that was the old MRs.

I have a LSA set up in my 24 Pantera. 78mph so far at only 5500 rpm.
https://cimg9.ibsrv.net/gimg/www.off...ba18fb57a.jpeg

LSA have enough torque for 1.5:1 gearbox, but atmosferic LS not.
Did you make any special modifications to the engine for marinating? What is the fuel consumption?

So I put about 150-200 hard hours on it and it needed a rebuild. I have the engine at a marine based engine builder now to set the bearing tolerances properly. I think the oil got too hot and wiped the bearings. So plans for next season definitely include a larger oil cooler.

The OP is long gone so this thread is sort of irrelevant as far as he's concerned and your case with the surface drive and your boat is obviously a one off situation more or less.

BUT to say in general an NA LS lacks enough torque, or doesn't work with "Z drives", is inaccurate info that'll be spread by internet BS.
It's case dependent.
Podunk is proof.
Do you realize every anemic SB 350 CI 260HP with an Alpha is in front of a 1.47/1.50:1 drive.
And every 300 HP 350MPI in front of 1.65:1 or 1.50:1 Bravos.
Even your LS376/480 produces 400 lb-ft at 2500 RPM according to the CPP catalog.

Are you saying a Big Block Chevy is big? Or archaic with the Mastodon statement?
If archaic you mean cam in block, pushrod, 2 valve per cylinder just like an LS?
(The LS with better OEM ports perhaps, but the aftermarket has the BBC taken care of.)
If so and also, you're arguing for torque but at the same time disparaging the king of torque. AKA, the big block Chevy.


So you slowed your prop speed down with the new trans then stepped up in pitch to recuperate and you gained 3 MPH?

1.) I reduced the propeller shaft rpm from 4,000 to 3,100 and gained much over 3 mph. I also explained why. Again briefly:

The propeller takes power approximately with:
- diameter to the fourth potency.
- rotations to the third potency.
- pitch to the second potency
- linear with the difference of the front surface.
This applies to all propellers that rotate in liquids, including e.g. for airlines. I work professionally with bigg propellers for air flows and I know what I'm talking about, although the language barrier and simplification may make it look different.

Since there is one whole potency at revolutions and steps, it makes sense to lower the propeller revolutions as long as this is technically feasible. For speedboats, the lower limit is probably somewhere between 2,600 and 3,200 rpm, I did not search what is the best and I used 3,100 rpm becouse of lot of good propellers for this rpm and Re numbers still alow relative small diameter of prop.
If you keep gear ratio and change prop pitch you do not make a lot. With to high rpm on prop shaft you always have conditions like if you drive your car in 6 gear on steep slope, even if you change pitch. (Diference on the potency for rpm and pitch.)

If you use an LS or LT with a 1.5 or 1.6 drive, you get at least 4,000 rpm on the propeller, and these are conditions that are suitable for very fast and light catamarans, not at all for a V speedboat. There is to much rpm and to less torque on the prop.
Put a Mercury 400 or 500 outboard on a speedboat over 4,000 lbs and you'll run into the same problem. It will be less succesfuly than 8,2-HO.
But why did Fountaine give 1.6:1 and not 1.5:1?

Volvo Penta gives the LS engines a gear ratio of around 2:1 and realistically achieves better results than the Mercruiser 8.2 HO. If you put a 1.5:1 drive on the same engine, it won't go anywhere because there will be too many rpm and not enough torque. I know, they do not race, but this solution alove LS to push bigg boats succesfuly like BB and this is the point.

2.) Technically speaking, all these engines are very outdated, be it SB, BB, LS, LT. LS and LT still have some advantages over the other two.

LS engines are truly an amazing accomplishment. GM had brass ones to keep pushrod cam engines in their flagship cars and got amazing fuel mileage with performance. Compare that to the BMW V8s that have DOHC and are massive...with unlimited common issues.

SBC/BBC will be the dominant marine engines until there is something better enough...and it's not here yet.

TQ and HP are essentially the same thing...representing the net energy produced by the engine. Peak HP has more energy than peak tq. (Typically) Less TQ is produced at peak HP rpm, but there is more speed...so more energy. Of course TQ is the rotational energy, and HP is the power, and we generally focus on TQ at lower rpm, and HP at the higher rpm.
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OK;

All Z drives and propellers are designed for arround 5.000 engine rpm. SBC and BBC are in this range.
If you take such drive for LS or LT engine, you have no chance to use all benefits of this engine. It turn over 6.000 rpm and prop rpm it is to high, that mean prop shaft torque it is to low.
For speeds arround 70 mph it is the best gear nr. round 2:1. In this case you have a lot of propelers with pitch betwen 26 and 34 inch.
For speds over 80 mph should be 1.6:1 ok, but only like twin on light boat. Or single on really light and small boat who go wery fast. Tuff did similar thing with single 450 hp outboard Tuff 28.

I will never say that SB, BB, LS and LT engines are bad, but they have old technology inside. Since there are no more suitable ones, I myself have one LS in a speedboat, but I would never install a BB!
Any explanations why did Mercury go away from SB and BB and start with good, modern outboard engines?

Plain market demand. The newer generations of boaters (as i see it) didnt have the exposure to the visceral experience of loud boats like we did growing up and having a show like Miami Vice going every Sunday afternoon.....or have neighbors that are gearheads tuning up a loud muscle car. These kids now a days are all about fast and furious and fart-can mufflers and/or saving the earth from burning down! :rolleyes:
The guys like me that grew up in those times are getting older now and moving on to easier things. Hanging upside down while the blood is rushing to your head and your eyeballs feel like popping out of your skull while trying to change a starter motor on an inboard engine is just getting old. Dont get me wrong...im still doing it as im only 52 right now but the bones are starting to hurt when i wake up and working on an outboard is looking more and more appealing ;) Wont be the same as any inboard open exhaust engine but that's life sometimes... :cool:

My friend fired up one of his 400 Merc OB's on accident on the lift while back. Now if they could get THaT sound some how-- it might solve some of us Old Guys problem for
Need For Noise :evilb:Fuk the Neighbors :lolhit:

LOL yeah ive heard some "ROWDY" outboard start up when dry.....i agree they can sound good! :D