38 scarab avs
 

What speeds would I pull out of a 38 scarab avs and how would handle in rough water with some 700 hp blower motors n bravos?

my 38 avs had factory 575sc with ext boxes would run 86. i would be scared of bravo 1's 700hp is not a question of are you going to break the drives but when!

was just curious cause i am tossed up between the hustler and the avs what boat would be faster and handle better at top speed and big water

Hustlers are fast hulls.

i have not drove a boat that handles the big water at high speeds like my AVS double step hull. its amazing

Hustlers are fast hulls, but depending on the year of the 388, the older ones were known to be a little squirrely at speed.

extension boxes
 

I see in your post you have extension boxes on your 38 avs want to know how hard they were to install and if you would recommend it, I have a 1999 38avs 800 hp motors and xr drives 31 5 blade props and hitting a wall at 87 miles an hour and wondering if boxes and shorties would help. I would be willing to go thru the effort to install the boxes
if I had some idea of what the outcome would be

interesting I have 800 n/a motors but have 32 lab 4 blades and I hit 92 mph could it be the 5 blades??

Standard length drives and 5 blades are probably hurting your speed. By adding boxes this will submerge the props in even deeper water, the boxes AND shorties would be the mod. You might want to try a 30 or 32 Bravo 4 blade before anything.

I have run bravo 32 4 blades and the slip on the bottom is worse the mid range is not as good and the top end is the same. did you put the boxes in your boat or did you buy it with them on.I know it is a lot of work and if I can find some buddy who has done it already and can give me some input as to what I am in for would be very helpfuff
thanks for any and all input or advise

now this is interesting my bravo 32 4blades are not lab nor are my hyromotive 31 5 blades are you running standard length xr drives

yes they are standard length but I have nose cones on the drives I run 54 mph at 3500 rpm and boat comes on plane with ease

we are not to far apart at 3500 I am running 55 mph did you run the boat with props that were not lab props and if you did how much difference did it make. I just feel like I have the hull and the hp I should be able to see 100 plus mph and if shorties and boxes are the answer along with a pair of hearings I am willing to do it. That being said I am not an engineer and if I do all this work and spend all this money and do not get the results I am looking for I will not be a happy camper . Do you know any buddy who has put the extension boxes on a 38 avs hull and if so would he do it again. thanks for the info I really appreciate it And yes I know if you want your boat to go faster just buy a faster boat

no never tried boat without lab did try with the 5 blade and it went slower than the bravo 4 everyone that puts shorties on boats all seam to be faster by 2 to 4 mph my motors dynoed at 804 with 790 ft of torque boat ran 96 at its best before I dialed them back to a safe setting this is in fresh water also

Any new info?
 

I'm curious if anyone never made the mods spoken of. Inown a 1999 38 avs with 700's. Best has been 85 with 30 Maximus and 86 with 32 bravos
​

Its not that hard to install an extension box once everything is out of the boat. If you are going with shorties then you can use a neutral box and use the original bolt holes. ( I raised mine 1 1/8 inches so I had to redo everything. Already running -3 IMCO shorties.) You just bolt the box on,then bolt the transom assemble to the box,then install the engine,check the alignment and install the drive. It really wasn't that hard.
The herd part was cleaning up all of the hoses. I ran my hydraulic hoses through the box. Less holes in the transom. Trim cable also.

You sure you have 700 HP? What is your prop slip?

86.9 sounds about right, around 650 for 85. not much difference from 650 to 700, 1.9 gain is probably it, maybe another couple mph gain in 3' choppy water getting hull out of water more. 38avs seems to be around 17% prop slip with bravo 4 blade. 32 pitch 4 blade 5200 17% slip 87mph, 88 with 16% slip. U are right there.

Did you ever get yours going with the new mills? How's it run now

Pretty sure

Problem is that you are loosing power up top. This my Zz572s/620 engine in 99 38 Avs. 30 pitch 5400/5500, 84/86 mph. Wouldn't pull passed that rpm. Your numbers are about the same.

My sheet shows horsepower climbing all the way through 5800.

Yes so did my Zz572s . 5hp increments with torque falling quickly, u probably need 700 at 5400 to notice a difference . That's not going to keep spinning prop faster it's not a car on flat ground. You had 19hp increase in 400 rpm engine might be making 700 but it only has 680 usable hp at 5400.

Hmm.... looking at the numbers you guys have posted here... I'm a little dissapointed in what this AVS I just built some 725hp NA engines for is going to run for top speed. I was hoping closer to 90mph but it seems like mid 80's is where it will be.

Baja226sport, is this Paul F.? Looking at your peak torque, I'm wondering more cam duration might be better for your setup. Looks like it plateau's around 4200. If you're spinning 5500/5600 WOT and even though the HP number are climbing (they usually do with blowers) I usually want to cam it so the peak torque range will be a little higher (say 4500-4800) from the setups I've put together.

yeah I don’t think u have enough to get to next barrier, either need more cam or possible retard cam 2 to 4 degrees and move torque higher up in rpm to push the prop some more. Probably 30 pitch 5500 as u are now.

I usually prop something like this 800-1000 rpm above peak torque so figure 5700-6000. It has bravo's so I can't lug it either.

What have you guys needed to do with the fuel system on your AVS's from the tank to the engines?

The boat ran 87mph with a small chop, 6 people on board and full of fuel. 28" Bravo 1, -2 Sportmaster, ITS steering/extension box, 5600 rpm. AFR is also rich (12:1) and air temp was around 90 with high humidity. 90 mph should be possible after some fine tuning with better weather and water conditions.

Saw this article the other day. I really like the 38 AVS setups

https://www.boats.com/reviews/speed-merchant/

Panther, how would you compare the ride and handling to a Top Gun or your 36 Apache? Never been on a 38avs

Tough Question.

I'd say it's very comparable to my Apache however, I haven't been on the AVS in any "really" rough water like I've been on in mine over the years. I've run with a few in rough water and they seem to keep up just fine but I also have a lot more power than any of the ones I've run with.

I will say that the AVS rides better in calm water than mine (no hull rocker). It's a bigger boat, both wider and longer as well as heavier than my 36'. This boat came in at like 13K lbs or something like that. It was weighed this winter while getting a new transom. Like an Apache, they need a lot of power to go fast.

Mid range on the AVS's isn't stellar. it has like 18% slip in the mid range and 11-12% on top (rough numbers). I attribute the mid range slip to not being "on the step" yet. Once you hit 4200 rpm the boat hooks up and really digs in and moves.

Of the TG and Flat Decks that I've been on, they all seem to ride very different. It could be differences in weight, balance and cabin configurations. Surprisingly, I haven't been enamored by them. I'd probably skip the 38' and go to a 39'.

We tried some 5 blades last weekend and they were a little tall so the RPM's were short and as such the speed was down considerably on top. Mid-range picked up a lot though. We're going try the next size down 5 blade and see if it finds a happy medium. We might even try a 1" spacer so the 4 blade works better mid-range. Other than that, the way it sits now, it'll be an 84-87 mph boat every day of the week with 90 mph on a glory run is my expectation.

One other thing about the AVS. I really think the Volvo DPX is the best all around drive for this boat. I rode on one a couple times that had the 600 dpx setup and it' performed really well.

New top speed; Small chop, less fuel and 4 people, 88mph

Sounded good on Rock The Bay!!