Prop/Drive Height Advice NSX
 

Hello,
I purchased a 2004 2600 NSX in February of this year. The boat should have around 750HP when the motor is complete. The current drive is setup w/ Imco 3" raised box, XR upper and Imco std length lower w/ 1.5 gear ratio. The previous owner had a 5 blade Hydromotive on it and mentioned it had a difficult time carrying the nose. I purchased the boat without a prop so we're starting blind. The prop shaft is currently 1.5 inches above the bottom of the boat. Any insight would be greatly appreciated. Thanks in advance! I'll try and post a pick of the transom if I can figure out how to do it correctly.

I read an article in Powerboat Magazine (2002) through American Offshore's website that the company offered a 650SC package from the factory with a Bravo 1 Drive, 32 pitch 4 blade and 1.36 lower gears that pushed the boat 104.4 mph at 5500rpms. Should that be a good starting point? The previous owner of my boat mentioned the boat didn't plane well with a 4 blade prop with the 3" box and that is why he ended up with a 5 blade. He blew a head gasket before he was able to find the correct prop and drive height. The engine won't be complete for another month. I'm having it rebuilt by Young Performance Marine. I'm looking for a setup that maximizes overall boat performance (planing, turning, overall handling and not maximum top speed). I noticed someone posted a youtube video of a green NSX with a Stellings Adjustable Extension Box. Does anyone know the owner of that boat? It looks like he's really got his boat dialed in. I'll post a few more pics of my new ride. I can't wait to get it back, this is going to be a fun Summer.

Here is the boat running when we picked it up, sounds awesome! The previous owner is a great guy that spent a lot of time and money on this girl. I'm not mechanically inclined so I took it to Young Performance Marine to dial it in. The whole process has been a lot of fun so far. He's putting new Gaffrig gauges in, and swapping the crank, heads, exhaust, blower, intercooler, etc into a larger bore engine block. I can't wait to have her cooking on the water. Will keep everyone posted.

Gauges in!

Looks good! Eddie does a great job

Thanks! Yes Eddie's the man. I call him at least once a week for an update and he'll bull**** with me over the phone all my about my boat. Good stuff. I'll keep posting pics of the upgrades as they come.

Canopies went from a canvas material cover to vinyl. What do you think?

Custom ski tow. Eddie's thinking outside of the box, pretty cool.

I saw your boat when I went to get my Talon from Eddie.I gotta say that ski pylon looks like something Eddie would come up with.I hope him and Travis have lots of fun with the "Ski Pylon " I'm not sure bout them two all couped in that shop all day you know ??????? hf...

Ha, good point! That ski pylon may cause a cat fight or two at the party cove on who gets to sit on the back of the boat:eekdrop:

You know that I don't roll like that.lol

I ordered a 32 pitch 15.25 Maximus prop today with a shortened diffuser ring. I'll post the performance data as soon as the boat is back together.

Short block coming together.

Engine painted

Engine tuned on the dyno

Engine back in the boat, looking good. Water test coming soon.

Have you tried to increase the negative trim. It worked on my 26 Daytona. I shortened the trim ram inner rods 3/4 inch and with a little cutting and grinding I got the drive to go down equal to 3/4 inch shorter rams. The boat wouldn't even try to get on plane with a 28 pitch 4 blade bravo prop. After I Tinkered with the negative trim it hops up on plane with the 4 blade.

I tried a stock 26 Maximus and it made the boat ill handling.

Thanks for the info Tinkerer. We took the boat out yesterday and tried a 32 Maximus and 32 Bravo 4 blade. It seemed to like the Bravo 4 blade better. Planing wasn't an issue which is interesting. We're going back out this morning because it was too rough from all of the boat traffic to dial in the fuel air ratio at higher speeds.

Eddie tuning the carb on the 4th of July. We're going back out this morning to dial in A/F ratio. Eddie Young is the real deal!

Here are a few more pics from my trip to Young Performance Marine last weekend. Eddie Young and his young apprentice Travis work hard for a living. We took the boat out two times dialing in the Air Fuel ratio and trying out props. We tried a Maximus 32/15.25 with a shortened diffuser ring and a 32 stock Bravo 1. The Maximus had so much bite the motor had a hard time picking up rpms to plane. The 32 Bravo planed much better but was really loose at speed with a lot of slip, We're thinking about trying a Hydromotive P5X but the previous owner mentioned that was on the boat before and didn't carry the nose very well. I wouldn't mind dropping the X-dimension down with a spacer and going back to the 4 blade Bravo. Any thoughts?

We talked with Art DiNick at American Offshore. It sounds like the drive is just too high. We're going to try a spacer and stick with a Bravo 1 style prop. Will keep you posted.

Rob, thanks for the ride Saturday. Popped my cat cherry! Boat is on rails at 90 MPH. Eddie and crew did a great job!.

Thanks Jeff, I'm really please with how the boat handles. It's not as fast as I thought it would be on the top end but overall handling is awesome. After a few WOT pulls I thought a saw 95mph on the GPS speedo. I hit the speedo recall option on Sunday while putting the boat away and it said 93mph. That's with a 3" raised box and a 2" drive spacer turning a 30 pitch labbed prop at 5400rpms. The slip is in the single digits but I think the drive needs to go up a little. The engine starts, idles and behaves like the 454MAG in my previous boat. Eddie Young knows how to build and tune an engine, that's for sure. Kuddos to American Offshore for building such a fun boat to drive, this thing's sweet!

What prop did you use and where is your shaft in relation to the bottom of the boat.

30 B1, prop shaft according to my measurement is currently 1 inch below bottom of boat with IMCO box

Thanks for the info, Are you using a thur hull water pick up or are you getting water thur the lower. I'm getting ready to start testing with mine gain.

The lower unit is IMCO SC with low water pickup.

Rob, the last day that Travis and I ran it, I squeezed 101 mph out of it. It was pretty warm (low 90's) but there was about a 1' chop and the boat loved that water.

I agree that it needs a 1" spacer instead of the 2" spacer. I went with the 2" to keep the thing safe and driveable until you got a little seat time in it. Let me know when you are ready and we can get the 1" spacer on the way. Be safe out there and enjoy it.

Thanks for the kind words.
Eddie

Nice ride, slight hijack for Eddie, how have the World Products stuff been looking since the PBM buyout?

Eddie,
Thanks for setting up a kick ass ride. We've been at Lake Cumberland since Saturday. We taught our 8 year old son how to waterski with the boat. We've been tubing and driving this thing all over. The motor is outstanding. This thing is turn key. After getting a little more seat time I agree this boat is a 100mph ride as is. I'm not sure I want to go any faster. Anyway job well done!
Rob

Rob, did you get your trim indicator working again? Glad the boat is working out for you. You've wanted a ride like this for a long time!

Yep everything's working, sweet.

Cool thread

Thanks. Here are a few pictures of the boat from last week at Lake Cumberland. First time at Cumberland, the lake is gorgeous.

I passed you guys heading north on 75 toward cincy as I was heading south to Cumberland Friday morning. I was hauling a 25 daytona

Yes I saw you as well, driving through some heavy rain. I hope you had better weather over the weekend. Nice looking boat!

Took the NSX out over the weekend. I found a drive height and prop that works great. The boat has an IMCO extension box. The prop shaft center is 1/2 inch above center sponson, prop is non-labbed 34 Bravo 1. Boat planes great, cruises effortlessly and gets to triple digits in short order. I love this boat!

It looked good out on the water Saturday running with that Eliminator. Congrats!

Does your setup have any chine walk at top speed? Have you ran it thru the prop slip calculator? http://www.go-fast.com/Prop_Slip_Calculator.htm