Thinking about adding an Imco SC -2 lower. Any experience with this setup? Prop advice?

Lot's of past discussion on the topic for 280's. -2 is too much. -1 MAY work with a 5 blade but inconsistant results. The shorties do work better on twins but still - is 1 to 2 MPH really worth it?

Gotcha. Talked with Kenny H this morning about it. He said there is a possible gain of a couple mph with the right prop and lots of time and money testing. Not really worth it in the long run. Not to mention the added stress on the drive and prop. There you have it from the man who would know.

Honestly, It all depends on where the drive hole was cut. I have never seen two 260 or 280 velocity's have the same X dimension, Seriously.... I picked up 5 mpg with a -2 SC lower w/shim but my drive was set pretty low from the factory. You have to look at it this way, if a -2 lower is too much you can always add a spacer. If you have it blueprinted it will also make the boat handle better and take some of the chime walk out. You can pick up a used SC lower for 2000.00 - 2,500.00. It's also worth getting a 6' straight edge to check the last 6 feet of the hull for straightness and to make sure you don't have a hook. Prop really depends on where you want your sweet spot to be and having it labbed and polished will make a difference too.

It really isn't that hard to pop on a new lower / prop and go run it. Testing is simple and there are several companies who have a prop testing program. I'm not really sure what you mean by added stress on the drive ? A bravo XR running 70 mph behind a VR1 will have the same amount of stress as a standard lower or SC shorty lower. The gears in both are essentially the same XR gears. If your running a stock engine and want to keep it stock, fine tuning your x dimension and prop is some of the easiest mph and handling improvements you could pick up.

I've talked with Steve Stepp at length when I was working on fine tuning my X dimension. Depending on the hull there is a target ballpark measurement where you want to be.

Kenny was referring to my VR1 in particular. He is very familiar with my VR's drive height setup. Going with the 2 shorty would be bringing the drive height too high in his opinion. The added stress would come from the prop blades breaking the water surface shock loading the drive and mainly the prop blades.

It all depends on exactly what your X-dimension is, do you know what yours is ?

The worlds fastest single Velocity runs 117mph, I would target to have the same X dimension as him. Mine is set the same and anyone who runs well over 100 is also very close to it .

I am curious, what is the magic number for x dim. ?

Padraig

[QUOTc.f.E=Padraig;4176284]I am curious, what is the magic number for x dim. ?

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I am curious also. I am thinking of going with a imco or sportmaster this winter and didn't know weather to go shorter or not.

If I could ofter one general piece of advice, always consider your goals for your boating when chasing top end. A max top speed drive set-up comes at a trade off on other handling and in particular planing off given the higher x. There's a reason race boats are set up different and often tweaked for race conditions. Even moving to the "faster" Hydro's from Bravo's on my 39' requires a special technique to get on plane. Ryan is correct that "Bravo style" lower units don't last nearly as long being surfaced with 5 blade props - even with experienced hands and just 525's prop shafts get twisted more often. Whether it's more horsepower or drive/prop set-up, there's always trade-offs and decisions as you chase the maximum number. But even though it certainly gets expensive, I guess that's part of the fun and our acquired experience!

Good post. Very true.