Props for 46

[splashandburn]

What props are you guys running on the 46's? I'm running stock 28P - 4 blades but not getting the speed that others say they're getting. Boat's an '03 with twin 500 EFI's with ProChargers running 5 psi boost and only seeing 4600 rpm and 66 mph. Any suggestions?

 

[Ratickle]

You're right, that seems very low for your performance package. What is the HP with that amount of boost?

 

[Cruz-N-Thunder]

2001 430EC with 575sci dynoed at 725hp, stock 32p bravo one, 85mph at 5300rpm. Seems like u have something wrong. When mine were stock and tired ran 28p bravo one at 5200 at 73mph. I am assuming you are a 1.5 ratio. If somehow a 1.3 ratio would explain how over propped you are. Otherwise something wrong. Tabs up and drives around 7?

 

[splashandburn]

You're right, that seems very low for your performance package. What is the HP with that amount of boost?

Not sure of HP but I'm guessing its gotta be around 600 HP or so . . .

 

[splashandburn]

2001 430EC with 575sci dynoed at 725hp, stock 32p bravo one, 85mph at 5300rpm. Seems like u have something wrong. When mine were stock and tired ran 28p bravo one at 5200 at 73mph. I am assuming you are a 1.5 ratio. If somehow a 1.3 ratio would explain how over propped you are. Otherwise something wrong. Tabs up and drives around 7?

Yes these are 1.5 ratio drives with tabs up and fully trimmed. The drives do have 2" spacers on them though which puts them pretty deep in the water - think that could explain why I'm not turning these 28's at a higher rpm?

 

[Serious News]

Hot Boat magazine did a test in July of 2003 on a twin engine 46 EC with 500EFI's stock. It ran "a consistent solid 70-mile-per-hour top end". In June of 1999 they tested a SC with the same power and it ran 73 with box-stock 26-inch Merc 4 blades and cruised at 60-mph at 4000 rpm.

 

[CarbonKevlar]

Check your bottom with a straight edge ,from the transom forward down the deadrise ,they have a tendency to prerelease ,you are looking for negatives (hooks) in the bottom. The straight edge should be 8' to 12' long.

 

[endeavor1]

My 43 with 500s and pro chargers is just took off would run a lot better than 66. I spun 32pitch bravo ones. Dyno sheet said over 750hp. M3sc @ 5lbs rinning a 1.5 bravo xr

 

[splashandburn]

Tried a set of 28P props yesterday that were labbed by Merc and spun those @ 5000 rpm but got exactly the same 66 mph. Not sure what to try next . .

 

[endeavor1]

That's 25% slip. Way to high. Is your speed gps? With 17% slip you would have been at 73. It sounds like you have a slip problem or your motors aren't making power. 5lbs on stock 500s should make 650 any day IMO and run upper 70s maybe 80.

 

[Ratickle]

Carbon Kevlar is right, you need to check for a hook in the bottom of the boat. Plus, if someone has added 2" spacers to the drives after it left the factory, I can't think of a good reason. Maybe they were running bad 3 blade props and now have switched to 4 blades, or the bottom is hooked (but that should make it plane off easier). Here's an outboard schematic, but basically you can check drive height by taping something straight to the bottom of the keel extending back alongside the drives, and then tape another straight piece onto the side of one of the drives. Check the distance between the two when they are accurately aligned. Then, let us know, and maybe even take a picture of your setup.

 

[Ratickle]

I should have said as close to the drive as possible, not the bottom of the keel. Even better would be to have the one taped to the bottom of the boat stop in front of the drive and the one taped to the side of the drive at propshaft centerline extend forward of the drive to get the accurate measurement of drive height.

 

[splashandburn]

I should have said as close to the drive as possible, not the bottom of the keel. Even better would be to have the one taped to the bottom of the boat stop in front of the drive and the one taped to the side of the drive at propshaft centerline extend forward of the drive to get the accurate measurement of drive height.

OK thanks I'll check all this out once I get the boat home. I did run a set of stock 26p props this weekend and boat ran much better - 5300 rpm and 71 mph. Seems like alot of rpm gain from a stock 28 @ 4600 to a stock 26 @ 5300 though?

 

[endeavor1]

OK thanks I'll check all this out once I get the boat home. I did run a set of stock 26p props this weekend and boat ran much better - 5300 rpm and 71 mph. Seems like alot of rpm gain from a stock 28 @ 4600 to a stock 26 @ 5300 though?

Something is wrong if you are only seeing 71 on blown 500efi. Are you sure your engines are making boost? Sounds like they are running weak if so. Timing? Fuel pressure?? What's the gauges telling you?

Call me if you want and I'll gladly share with you how mine ran and indicated with M3SCs on it or my 46 with 700s.
870 623 434five

Chris

 

[Ratickle]

If the engines are stock except for the boost, their peak RPM should be around 5200. Before you were under the max hp rpm range, so once you got to the optimum rpm for the configuration of the engine, it could have made that much difference. You'd be shocked at the difference a quarter of an inch will make in one of our race boats.

I still think you are a little low on speed for that package. I'll be really interested in the shape of the bottom and the depth of the drives.

Also, unless a prop has truly been blueprinted by a reputable prop shop, you really have no idea of how good they actually are.

 

[splashandburn]

I still think you are a little low on speed for that package. I'll be really interested in the shape of the bottom and the depth of the drives.

I plan to get the measurements in another week once I get the boat back home. I know the drives must be deeper than normal since its running with the 2" spacers on them. I'm planning to take those off and see what that does for the performance numbers.

 

[splashandburn]

Something is wrong if you are only seeing 71 on blown 500efi. Are you sure your engines are making boost? Sounds like they are running weak if so. Timing? Fuel pressure?? What's the gauges telling you?

Not sure of timing but fuel pressure is 40 psi and boost gauges are showing 5 lbs of boost @ WOT.

 

[endeavor1]

Get rid of the spacers. That's gonna be your problem I bet. I remember talking to the shop that repoed/mechanics lei end your boat from the previous owner and they stated the previous owner had those added to try and bury the drives and keep them from breaking. I misunderstood you and thought the boat already had those removed.

Good luck and let us know how it goes.

 

[splashandburn]

So whats the thought on burying the drives? Isn't that going to put even more stress on them?

 

[Coolerman]

2" spacers on that boat is a no-go...... The 2" spacer would keep the prop from spinning up if you are jumping cruiser wakes and didn't want to throttle it.

The boat will probably not only go faster without them, but probably handle much better to. I would even consider -2 shorties and 5 blades.