Prop Upgrade
 

I've done some research and planning to replace the factory 3 x 3 26p Bravo III props with a set of 4 x 3 25p props on my 2005 370 SS with 496 HO's this offseason. I know if you're looking to squeeze every last mph in a performance boat with big HP, going to a place like BBlades for the props would be money well spent. While my boat has the Fastech hull, most of our boating is cruising in the 3500 - 4,000 rpm range. I've been on BBlades website and they sell the Mercury Racing XR Pro props that have the extra cupping designed for the heavier boats with Bravo III's. Does anyone have an opinion on whether I'd be worth the extra $$ to have them labbed by BBlades or will pretty much any local prop shop do for my needs.

Why the upgrade?
 

What's the performance gain you are looking for with the prop change? Higher top end? Higher cruise speed? Just curious, I don't have any prop experience on my 370.

I'm mainly looking for better cruise (same mph but lower rpm). Also, when I trim my drives for best mph at cruise with the current props, the bow gets very light and I get a wave induced purposing action which is annoying. Trimming the drives down and/or adding a little tap generally corrects this but I loose a mph or two. I'm also lookin to get a little extra bite around the docks and don't want to lose any top end mph if possible (I've seen 56 mph with a light load). From what I understand the 4 x 3 XR props should get me all this. I guess my question better stated is, should I run them stock or are there measurable gains to be had by having them worked on?

Sounds like a good plan, I'd be interested in the change in speed at 3600 RPM at 35-37 MPH which is where i like to run. The hull runs better at 40 MPH but I don't want to run at 3900-4000 RPM at cruise, just seems to high an RPM for such a big motor.

This boat has changed the way I trim, keeping the drives at a nearly flat has given me the best speed vs. rpm. As soon as I trim up to get the bow out of the water I have to apply a lot more throttle to keep the porpoising at bay, or tab a bit which works well in chop but just cuts speed in the calm stuff. Eventually I decided that this boat runs flat, the steps do their job and the vertical bow motion is reduced. I can get 4800-5000 RPM at WOT with 53-54 MPH on the GPS, don't think it's going to go any faster without more power and prop. I'm in fresh water, that might effect top end a little bit.

Great boat, doesn't seem to care if I have 10 people or just the wife, the boat loves to go.

Doug, you expressed exactly what I was thinking also. This hull really seems happiest going 38 - 40 mph. I can run those speeds turning 3700 - 3800 RPM (I'm in brackish water) but like you said, seems a lot for these big motors. I would love to get those speeds turning 200 - 300 less RPM. I have a friend who purchased the identical boat as mine but has bottom paint (mine does not). His came with 3 x 3 28p props and surprisingly his cruise numbers are the same (mph and RPM). And his top end mph is about the same but at about 400 rpm less.

We got our first full season in with the boat this past summer and I can't say how much we love the boat. Really was everything we wanted and more. We've had as many as 11 people on the boat and hardly noticed a difference in the way it drove.

just sent pics of the 25 XR props. Ran WOT 62 MPH at 5100 rpm and cruised 40 mph at 3400 rpm with 496 mag ho on my 38 fountain.

Running at 3600 rpms vs 3900-4000rpms will make no difference to the longevity of the engines.
The most important thing is to make sure the engine is propped to run the correct WOT rpms. The closer to the upper recommended rpm the better.