Ya this LS stuff is a bit challenging with so many tunes and cam grinds available. Im just trying to figure out how many blades I can spin with x given torque/hp Based on my experience, roughly 550 HSP will spin a 4 blade 83.5" R. This doesn't mean build an engine that makes 550 HSP at 6200 RPMs an...

Power loss or thrust loss? Are you comparing a 3 blade to a 4 blade using a 2.68 or are you comparing different ratios to a 2.68? Trying to understand what you are asking.

How many RPMs do you plan to run at WOT? This answer will help determine the gear ratio. Also a 4 blade is a better pusher prop than a 3 blade if you have the HSP to turn it.

That 540 must be making some HSP to turn a prop that big.

Been busy lately with work. Getting back to this thread. So I don't plan to spin 8000 RPMs. The max will be 7000 RPMs. Hopefully I will get a little more longevity out of this motor. :shock: The interesting thing is the LS7 comes from the factory with a 7000 RPM rev limit. The LS2 from the factory h...

The cam is one part of getting the direct drive to respond and run like it does. Why would Water thunder give away his cam spec's? My engine idle at 650 rpm's. The cam lope goes away at 900 rpm... Propellers tip speed is your limit here, the longer the prop, the faster the tip speed at the same eng...

Does anybody know the specs on the cam? I think everybody knows the answer to that.

So why do you think it was a radical cam? What RPM did it idle at?

It is what it is...it aint a full racer, but it is a fun boat to ride, performs amazing well, snaps hard. Remember its about 20% displacement disadvantage to a 0 540 Those thrust numbers were on tester, not a boat.....No cage etc in the way. The 3 blade Alpha is the only prop we tested that work in...

Here is the latest on the LOW TORQUE LS Build. Got the main bearings installed: https://southernairboat.com/wp/wp-content/uploads/rtMedia/users/171/2019/06/0518192206-800x450.jpg Torqued the inner studs to 60 ft lbs and the outer studs to 50 ft lbs. The side bolts were torqued to 20 ft lbs. Next ste...

Figured I'd stir the pot, been a few days and I was enjoying this thread lol https://youtu.be/u-MH4sf5xkY That video does a great job of explaining the science. 8) All the BIG TORQUE guys need to watch that video. :shock: Now I will say that airboats are different from a car because an airboat can'...

I really didn't expect much useful input on engine mounts from a CM guy, don't ya'll call em motor mounts or something? Watch the whole thing for sure, always good for more laughs. But I think Ricky was talkin about gear box boats at 54 seconds on the timeline. :stirpot: :stirpot: https://youtu.be/...

You just need to bite the bullet and put a gearbox on that A/C motor. Just think of all the prop shaft torque that you could make with a gearbox. A 1.5 ratio would increase the prop shaft torque by 50%. That is a game changer.

CMB, All good for me, a couple thoughts. Between #5 and #6 I say sure. I think you are sand bagging on #6. With 2.88 of gear your set up is gonna make more prop torque early on. The "Theory" that I am proposing is that thrust is going to be reasonably linear with the engine torque curve during prop...

Here are the main caps, main bearings and ARP main studs for the LOW TORQUE LS: https://southernairboat.com/wp/wp-content/uploads/rtMedia/users/171/2019/06/0518191605-800x450.jpg The main caps are stock LS main caps. Nothing special. P/N for the ARP main studs is 234-5608. Main studs are made from 8...

So we agree on items #1 thru #4. How about this for items #5 thru #9: 5. Measure on the thrust tester the time it takes to go from idle to 1000 foot lbs of thrust. If your BIG TORQUE A/C motor can't make 1000 foot lbs of thrust, we will drop to 900 foot lbs of thrust for the test. 6. Quickest time t...

Slidin Gator, You stated the following in other thread: "I certainly did, no doubt higher HP produces higher static thrust. Thrust needed is a function of the hull, friction and the load. I spot you top thrust king on the thrust tester vs. my 500 ft-lb motor. I am interested in the thrust response c...

Slidin Gator, You stated the following in other thread: "I certainly did, no doubt higher HP produces higher static thrust. Thrust needed is a function of the hull, friction and the load. I spot you top thrust king on the thrust tester vs. my 500 ft-lb motor. I am interested in the thrust response c...

Here is an update. Got the LS2 block cleaned: https://southernairboat.com/wp/wp-content/uploads/rtMedia/users/171/2019/05/0518191330-800x450.jpg This is a used block. There was a plug along with sealant in the oil dipstick hole. I think it was run as a dry sump in a car. I plan to run it as a wet su...

HP makes thrust, not torque. I guess them gear boxes are just a scam and everyone needs to get rid of em. All they do is increase useless torque, add weight, lighten your wallets and waste that precious HP. Just all negatives it turns out. :scratch: Really? You know better brother.... Gear box just...

I would also clean out the brand new tank after you get it. I have seen several brand new tanks with enough metal shavings in them to clog the filter. This happens more than people realize.

Yes, I was never planning to do a DD. Plan to run a 2.88 ratio with this motor and spin it.

Here is the latest on the low torque LS build. Decided to use the following cylinder heads: https://www.texas-speed.com/p-7650-precision-race-components-aftermarket-ls3-as-cast-cylinder-heads.aspx Planning to get the stainless hollow stem intake valves with 0.660 dual springs. The intake runner is 2...

Was that 427 LS on the dyno an LS3 or LS7?

It is also a good idea to install a wideband O2 sensor so that you can keep an eye on the AFR while you are driving.

Challenge heard and accepted, Game ON! We still need to negotiate the terms and the win/lose/draw basis, but I am in. Real busy with work this week, so I will just have to let this all fester until later. I will post my counter challenge later this week and we can all pick sides and start trash tal...