What's better, 50# lighter or 40hp more?

[signcoc43]

Id love to find a geared 480 like terrys motor than a 540

[Tony480]

You figure a dollar more per gallon. I payed 4.35 per gallon for 100ll. That would be about 20 bucks more every time I bought fuel. A lot of C/M's have 40 or more gallon tanks. That's not really a selling point in my eyes. Convenience of buying A/V gas and Oil would be at the top of concerns. My current boat runs great but next time I'll have another C/M!

Where is Av Gas $4.35/ gallon?? I would stock up! It is $5.99/ gallon here.

At the airport in Apopka

[Bruce]

go av 540 why not have the extra ponies and better cylinders not to mention an av just looks cooler if you can swing it dont buy somethin off the back of someones boat that has had the snot run out of it then got a degreasing and krylon overhaul lots of snakes out there

[Hog Guts]

Thanks for all the feedback. I know all this has probably been discussed a thousand times, but when I'm about to spend the money I like direct answers

So I've spoken with lots of folks and the general consensus is O-540 Straight Valve Wide Deck. I think thats my current direction. Next item of interest is the pistons. There are basically standard ones then 10:1 higher performance. I'm on the fence with the AV gas. If thats what it takes then I'll deal with it, but I have to tell you being able to stop at any gas station between here and there is nice without having to go out of the way tot he airport - forget the price difference, its the convenience more than anything. Is it good for the engine? Seen those threads don't need to go there again. I used 93 in the 520 but I Its sorta weird saying it worked fine after my motor unraveled the other day - even though that had nothing to do with it.

Is it worth the difference going 10:1 pistons? Does it make the motor any less dependable? Whats it do for me performance-wise? If I really can drop 93 in the lower compression engine if I happened to be in BFE etc it would be nice to know I could...

[ptr34]

10:1 will need avgas for sure. Plus you add cost of 1500 for pistons. If u get new ones

[Bruce]

10 to 1s in a straight valve so you can make the same power as the angle valve with a cylinder that doesnt hold up to heat as well this really doesnt make sense to me go with the av you can mix fuel in them should run straight av but in a pinch it can be done i wouldnt try it with a 10 to 1 motor

[fl cracker]

If your going to run the dog piss out of it hunting the 10-1 pistons will make more heat. My last SV 540
Had stock pistons, I don't think my current motor stands out in performance over the stock. Could be just me tho! Terry is was talking about LS fuel consumption, I know the ECO is good on gas.

[Hog Guts]

I'm sure you have a super healthy strong motor. I'm sure it's a fantastic deal. Me personally I'd rather buy a newly rebuilt motor with the warranty / backing of a reputable builder for <10k and add what I need to complete the project. If I were just looking for a deal and save money I could fix what I have for a few grand without doing the rigging over as well. Thanks for the offer though.


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[Outlawaircraftengines]

I have a GO-480 same as Terrys engine with 350 hours since aircraft overhaul for $4000.

[ptr34]

Dont know if he can handle all that power gary lolplus it wont fit where his 520 was

[Outlawaircraftengines]

10:1 from stock make a pretty good difference. Maybe between 100-200 rpm depending on engine and the throttle response is night and day. Av gas is a must with that and you probably will only get 75% life out of your jugs which is still ok. Ive built several with 10:1 and have not seen any cylinder issues with those yet, some are going on 6 years.

[Outlawaircraftengines]

8:7:1 on a stock a/v. 8:5:1 on a stock s/v. You can put the 10:1 (11487) in the a/v, but those are costly and made of gold. lol

[Southern Style]

I think you WOULD see a difference in 40 more HP... A SV 0-540 is ballpark 260 HP and a normal 0-470 is around 235... That's 25 HP... Now, ask anyone who has had a 470 and 540 and see which one they would pick,, Honestly, my last 2 boats were 540's.. And the new boat is a 470. Hell, the wife knows nothing about airboats, and she says she can see the difference in the 2 running dry ground.. NOT MAJOR enough not to own a 470, but enough to say, "Man, I had just a little more UMPH with the 540"... Still a nice motor and boat, but then again, I quit running 4 folks on the boat and went back to just me and the wife, so that 470 is plenty the motor.. But back to your question, the SV 0-540 is a pretty reliable motor like said before.. 25 HP is noticeable, much less 40... Your choice boss, Sorry bout the slow reply to your PM.. Was in Ga hunting several days over the holidays.. Good luck, your in the right place for questions and opinions !!

[gchuckie]

If was to build another motor it would be a 9.1 sv fuel injected motor. If yor not wanting to race up and down the river, and if your looking for something to run the hill and hunt out of me personally I would have a lower compression 93 octane motor. You could put some other goodies inside the motor instead of adding the higher compression. Jmo

[Bruce]

or just have the 300 hp to start with with a stouter cylinder

[Packman]

If was to build another motor it would be a 9.1 sv fuel injected motor. If yor not wanting to race up and down the river, and if your looking for something to run the hill and hunt out of me personally I would have a lower compression 93 octane motor. You could put some other goodies inside the motor instead of adding the higher compression. Jmo

X2

[P.Vento]

I have 4 540's and my personal experience not what I've heard through tribal knowledge or other bs is that the sv cylinders are tougher and handle heat better than the av, and yes I notice a difference in the weight of my wide deck motors and my narrow deck motors when I switch them on my boat, and yes they are all running motors, from 9:1 to 13:1, and yes they are all for sale, I'm building a supercharged ls

[Seven3]

I have 4 540's and my personal experience not what I've heard through tribal knowledge or other bs is that the sv cylinders are tougher and handle heat better than the av, and yes I notice a difference in the weight of my wide deck motors and my narrow deck motors when I switch them on my boat, and yes they are all running motors, from 9:1 to 13:1, and yes they are all for sale, I'm building a supercharged ls

I know the weight difference between AV and SV cylinders themselves has been discussed a lot, but what is the weight difference between narrow deck and wide deck cases? So what would you estimate is the weight difference between a narrow deck SV 540 (lightest configuration) and a wide deck AV 540 (heaviest configuration)? I know the wide decks are newer, but I've read several places that the narrow decks are less prone to cracking in certain areas of the case (which seems odd to me because wide decks are built thicker in areas)?

[Seven3]

I just found it again...on the vansairforce aircraft site it says the narrow decks are less prone to case cracks, specifically under the #2 cylinder mounting flange where wide decks are known for developing a "smiley face" crack. I've read this a few places, does anyone have some input on this from an airboat perspective?

[Outlawaircraftengines]

yes, wide decks crack more around the number 2 cylinder down to the bottom of case. Sometimes up to the top on the oil journal. Narrow decks not so much.

[Seven3]

Thanks Gary. Do you have a rough idea of how much lighter a narrow deck SV is compared to a wide deck AV?

[krazymatt]

Gary Barber has some good deals going on for a 540 this month..