Prop slippage is killin me!!!

[VegasHallett]

I'm having problems with major prop slippage and tried many things. I need a little help and maybe even try a 5 blade prop. I have the following prop info for anyone that can help:
1999 270S Hallett (step bottom)
Motor 502 with Whipple
Outdrive Bravo XR
Fuel level 3/8
Gear Ratio 1.5
26 pitch prop (4 Blade Bravo SS)
71.6
5200 rpm about 16% slippage
28 pitch prop (4 Blade Bravo SS) (3 blades were 27.5 & one 28)
75.3
5050 rpm 15% slippage
Sent the 28 pitch prop to a prop shop and had it trued and cupped
28.5 pitch prop
70.4
4800 17% slippage
Obviously the 28.5 prop is too big for my boat and I was thinking about running a 24P or 26P 5 blade prop, which will keep my RPM's up and inturn keep the Boost pessure up on the supercharger. I'm just wondering if I have enough HP to pull the extra blade. I'm trying to get down to 10% slippage or less. Any suggestions would be greatly appreciated?????? :cry:

[Havasu Hangin']

10% or below is in the cat range...pretty tough to get a v-bottom in that range.
Where is the propshaft in relation to the bottom? How much are you trimming it?

[VegasHallett]

The X dimension is higher in a step bottom then a regular V Hallett. If I make any type of turn I get pretty good prop burnout. I trimed the drive out just until the GPS shows a decrease and then I bump it back in slightly.

[Havasu Hangin']

The X dimension is higher in a step bottom then a regular V Hallett. If I make any type of turn I get pretty good prop burnout. I trimed the drive out just until the GPS shows a decrease and then I bump it back in slightly.
Loose = fast
There's a fine line between a high X and speed tradeoff (slippage).
What is the diameter on those 4 blades? If it were me, before I went to a 5 blade...I'd go up 1/2" on the 4 blade.
Standoff box?

[VegasHallett]

My Bravo one diameter is 15 1/4" (stock). Since I have a step bottom, I was told never decrease the diameter from stock. But is it worth adding diameter to a Bravo one prop or maybe just go with a differnt prop confiuration.

[Havasu Hangin']

My Bravo one diameter is 15 1/4" (stock). Since I have a step bottom, I was told never decrease the diameter from stock. But is it worth adding diameter to a Bravo one prop or maybe just go with a differnt prop confiuration.
Have you asked Hallet?

[Trailer Park Casanova]

Where is the propshaft in relation to the bottom? How much are you trimming it?
There it is.
Is the Jesus nut on the shaft lined up with the bottom of the hull.
That is, the center of the prop, should be at the bottom of the hull.

[Partycattin]

Curious,
If you need more HP to run a 5 blade, why would they come on a Chaparal deckboat with a stock 7.4?

[VegasHallett]

It's all about the pitch on the 5 blade. 5 blade props usally reduce prop slippage, however the extra blade increases the drag in the water (reduce top end). The 5 blade prop on a 7.4 deck boat is probably not even a 24. I'm pondering if I have enough HP to pull a 26p 5 blade maximus with a whipple.

[scarabrick2]

ttt

[LHC30Victory]

Call Julie at Throttle Up in Fl. Do a search here or on OffshoreOnly.com for them. Or call Bronson Hill. Both places have great reps and know their wheels.

[phebus]

No Ka Oi, I never get tired of you posting pics of your boat. Beautifull.

[pussywuped]

Vegas Hallett,
I had the same problem with my tunnel, As you can see from the graph insreased diameter helped my mid or low range cruise slip numbers. Also use 1" less pitch when calculating your slip with a Bravo this will help with your numbers. http://www.***boat.com/image_center/data/520/2457graph_boat_Page_2.jpg

[ToMorrow44]

I have that same problem with mine. All the bravo I's tend to have a 17%+ prop slip. The 30p lab spins 5300rpm at 83 but then going down to a 28 lab doesnt really increase speed, just rpm because the slip is so high. Tried a Hydromotive P5-X and that worked horribly. It drove the nose of the boat down and picked up the back end and wanted to bow steer a lot. It also only spun 4800rpm and went 75. The best prop so far is the new 25p revolution 4 from mercury. It acts a little like a bigger prop but still way too small for my boat as it was on the rev limiter at about 3/4 throttle. It cut the slip down to about 14.5% which is awesome and it gave the boat a lot of bow lift which is what Vs need. The ideal range for slip is in the 12-14% range regardless of cat or vee. Getting any lower than that (besides being very hard to do) is very hard on the drivetrain of the boat.
-Tom

[STV_Keith]

If you're in Vegas, call Kevin at R&R Prop and see what he can do for you. 702-564-7502.

[VegasHallett]

If you're in Vegas, call Kevin at R&R Prop and see what he can do for you. 702-564-7502.
Kevin is the one that worked on my 28 to begin with. I went by his shop this Friday to drop off the prop again. He is going to put it back to a 27.5 and rework the cup on the trailing end of the blades. That should get my RPM's back up to 5100 + and give it some bite. Kevin seems to be a stand up guy and hopefully I'll get back up to speed.
I talked to Throttle up on the phone and they stated 16% is not that bad for a stock Bravo XR. With some tweaking and luck I might see 12%. The guys at Throttle up help out a lot and sure know their stuff about props. :rollside:

[VegasHallett]

I assume your stats are based on runs at Lake Mead? If you are getting 71.6 with your 26 pitch prop @ 5,200, I'd say that is great! I don't know much about anything except I have a 270 with a 525 and 26" pitch also, which is almost identical to your set up except I do not have a whipple on mine. In July on 2 separate trips, I was only able to achieve 63 mph @ 5,000 rpm with my 270. However, I consistently hit 73 mph at 5,100 rpm (with full tank, and as many as 5 people avg 200 lbs) when I ran from Long Beach to Catalina and also at Havasu (in April, cooler weather).
I'd be happy hitting your 70+ speed at Lake Mead even with the slip.....
I'm sure altitude and temperature has a lot to do with it...
When I was doing my test runs at mead on July 17th it was 114 degrees ambient temp. Right now I'm working on how to get some fresh air into the engine compartment. The original engine compartment air flow design has its flaws
I can't wait to see what it does when I take it to Catalina later this year. Since boats are a little more buoyant in salt water I should have some more fun.