Dragracer_Art

Wife and I came home with this gorgeous 2007 Chaparral 256ssx a few weeks ago. It came with a 375hp Volvo Penta 8.1 Gi and DPS-A duoprop outdrive.
Finally got in on the water two Fridays ago and it runs great. Managed 55.4mph on the GPS pretty effortlessly. Might have hit 56 or 57 if I really played with the trim... but wife was already annoyed with the wind in her face.

Any normal, sane or rational person would be tickled to have a 55mph 26ft bowrider... but coming from 30 years of hotrodding cars, building big blocks and drag racing on the 1/4 mile... I want faster than 55mph.

Unfortunately I didnt do enough homework before buying the boat. Originally wanted this same hull but with Mercruiser 496HO power. Unfortunately Mercruiser power in this model is rare... and the HO version even more rare... so I compromised and at least still got the big block... but it is Volvo Penta... which means almost ZERO aftermarket support.

I am in talks with Larry Hofer at Raylar Engineering and he tells me I need to find a GXi ECM for the easiest way to make his stage1 525hp top end work... so that hunt is currently ongoing.

Other thoughts are...
I currently have F6 props (24pitch) on the boat. It jumps on plane and powers to 55mph without a struggle at all.
I am wondering if I can just do a simple jump to the F7 props (26pitch) and pick up a few more MPH since the 8.1 is a torque monster... or if this will just load the engine more and hold same speed at lower RPM.
I already have a pair on order (found them cheap @ $750)... so either way... maybe they will work better with the Raylar 525hp upgrades.


Any thoughts on this ?
And please dont say... "Leave it alone"... because I CAN'T leave it alone. Not even possible.

bencini231

Sorry to say this even though you said don't say this.... I would completely leave it alone or replace it with a 502 based engine. The 8.1 platform is not a very cheap build and I have seen way to many builds go wrong on the 8.1's.

Dragracer_Art

Duly noted.
I can always just build a 572/598 combo on a MKIV platform. Might be cheaper in the long run.

ICDEDPPL

You can throw a bunch of money and power at this hull but in the end you won`t be happy.
Anything power wise that will make a difference will blow your outdrive so then you go down that rabbit hole. It`s a deep and expensive one.
Basically you have a 10 bolt and you`re trying to throw a bunch of power at it , Its not going to last and upgrades are $$$$.
That hull is not made for speed either.
Either enjoy what you have or get a different hull.


not on this site

techman

That motor will have a hard time spinning an F7 prop set. You RPM at WOT will be greatly affected. That boat is setup perfectly as it...don't spend a dime on chasing speed with it...it ain't gonna happen without a motor transplant and your "gorgeous" bowrider will be a lab experiment that no one will ever touch down the road.

Sorry, just not the platform for speed.

Dragracer_Art

And that's what brought me here.

F-2 Speedy

..........

Cap'm Kurt

Techman and Icdedppl got it right.

Only thing is, is to check that your WOT rpm is near the top end of your recommended rpm for that motor. Otherwise it will feel more sluggish than it should. Very simple idea, but so many dont understand that concept, or have never even checked it. But chances are what you have is correct.

Dragracer_Art

It is approx 4500-4600 @ 55mph... so yeah it is spot-on and does run like a beast for a 5500lb boat. Last boat was a 5.7 merc and was all done @ 42mph. Nothing I did to it made it any faster. Tried a set of Stainless Marine manifolds/risers, Holley carb, new DUI HEI distributor, etc... and it still only went 42mph.
The new 350 I built for it never made it into the boat... as I sold everything and got back into a big block platform. That got me out of an underpowered smallblock boat and into a strong running big block boat.
My problem is... I like to make everything better/faster... hence the reason I am here.
I gave up on the F7 props. The ebay seller flaked on me and now i am doing battle trying to recover $850.
I will likely just build a whole 'nuther engine for the boat and prop it accordingly.
Wife and I really like this hull layout. We shopped several months for the right deal and paid $45k for a $60k boat.
I would be happy if I could squeeze another 10mph out of it with a healthy big cube combo.

speicher lane

You will be farther ahead selling a stock 55mph Chappy as a 55 mph day cruiser and just buying an 80mph performance boat - less money/ headaches and you know what you have under you without settling for 65 or 70mph steps each time you want to go faster.