Modifications
 

I have a 1996 scarab. My prop shaft depth is 8" at the moment with the stock bravo one. I want to install a -3 imco lower. But have heard that I'll have to modify the upper. I also have thoughts about an ext box. But from what I've read I don't think I'm gonna go that route. Any advice will be appreciated, thank you. Travis

the guys on this site who are really in the know about set up, first need the length, model, single or twins and hp and what props before they could suggest a route to follow

It's a 26' scarab with stock bravo one, 26p labbed prop, 672 hp n/a 540.

this could get good

Why you say that. Lol.

What complaints do you have, and what would you like to better

They are a 26 degree deep V right?

It is a deep V don't know the degree tho. It's a 26 foot scarab. I don't have any real complaints so to speak. But at 5300 I'll 75 all day. My peak hp/tq is 5800. But can't reach it with the 26 I have. I'm trying to figure if I bring my prop shaft depth up to 5 from 8 would I run better and more efficient cruising.

I do have a stock bravo 24p prop but I run out of rpms. So I know 26 is what I want just want more R' s. So I think with the -3 shortie lower I can get what I want, but I've been told that I need to modify my upper to make it work.

It may work but there is also the very real possibility your prop wont be right at the new height either.

Right, I was thinking of looking at trying a 28 with the new lower

-2" and there are no mods needed to the upper to clear the propeller. It does sound like -3 is where you want to be. You'll lose leverage and it might be harder to keep the bow up. Yes, this could get interesting. Let the Scarab Gurus hook you up with what to do.

Yeah I'm not 100 percent what I want to do. Its def a heavier boat then some.

Something doesn't make sense. what rpm do you spin the 24p? and 672HP should be way more than enough for the 26 on that hull, your slip is very good for mph. sounds like a real peaky torque curve. we need a motor guy to look at your dyno sheet.

because it is a cool boat with big power,

welcome to oso, before your done you'll be posting similar vides

https://www.youtube.com/watch?v=TmqvQCPlUAg

I can turn the 24 to 5800. And I peak both go and tq at 5800 To 6k. But I struggle to get it with a 26. Idk if I need to find a 25 and try that. Or shorten the drive up a Lil to relieve some drag.

I got ya bud.

Find someone with a -2 that will let you try it. I am running a -3 and it isn't that much to modify the upper. I have a -2 also that I have as a spare.
I wouldn't think that 5 inches down should be a problem. You will not have to trim it anywhere near what you used to at 8 down.
An IMCO extension box should help also - Increased bow lift for more efficiency.
The boat should handle better at top speed because you won't have to trim as high.
do you have tabs? You may need them.
I used to have a 34 SCARAB and put -2's on it.
I only gained about 1 MPH but handling greatly improved.
I did have to go to 4 blade BRAVO props. (28 pitch)
boat came with Mirage 3 blade 25 pitch.
The deeper drive will improve cruise but hurt top speed.
The higher the drive height the harder to get on plane and the more slip you will have at cruise speeds.
I went from the -2 at 1.5 ratio to the -3 at 1.34 ratio on my current boat and also added the IMCO neutral extension box.
BUT - I am running the prop shaft 2 inches ABOVE the bottom of the boat.
WITH only a 4 blade BRAVO prop.

Sounds good, I do have tabs. I have 30 inch k planes. And I thought the ext box would put the drive back down in the water. Cuz I thought about that too. Getting a -2 and putting on a raised 3 ext box.

The -3 WITH the box I think would be perfect. ( neutral box or 3 inch rise NOT installed for rise.) You can always lower the box or easier to add a spacer to the drive.

When you say neutral box, that's just straight right. Does nothing else but extend.

Right
If memory serves me My Scarab 34 had the drives down 5 inches.( with the -2 drives) BUT it was a twin. BUT it weighed a LOT MORE than your 26.

Ok cool.

I would start with a -2. Lots more used ones available and you don't have to modify the upper.