Rage

Guys, I just talked to the Mercruiser mechanic. They checked out my Nordic Saturday both in the garage and on the water. The tachometer is dead on 1000-5000 rpm and no fault codes!

Any ideas on a next step?

Thanks!

ComfortablyNumb

Hi Rage,

I too am somewhat of a rookie. I moved from a 20' Ebbtide to the 25' Rage. I read the tests in the magazines also. I realize that I wouldn't be able to duplicate their reported speeds, especially at 5000'. I don't have a digital tach. I can probably only guestimate my rpm's within 200. Between the markings on the guage and trying to drive faster in a boat than I ever have before I can only be approximate on the engine speed and plug that into the slip formula. I'm sure on any given day the existing conditions can affect your top speed by a couple of mph or more. I read about true pitch being 1" less than advertised but I've never heard that before and then you take a look at the mercury website and their calculations also try to take into account for "cup". Then again I'll bet that the percentage of slip changes the faster you that go. Whatever . . . . . . . ., I guess it comes down to satisfaction. When I was deciding to buy the Rage I ran the numbers based upon the magazine tests. I then factored in my gear ratio, (1.65) and pitch (24") and came up with a speed in the low 60's. With my wife reading a garmin hand held gps we were running 65 mph plus or minus a couple of tenths. We've repeated that on more than on occasion in good conditions.In average conditions I was able to run it up to about 63 mph. So I've met my expectations that I established when I purchased the boat. This also indicated to me that the slip calculations based upon the magazine tests where reasonable. The Rage is a light boat with a good bottom. To me it would seem that the low 70's would be a reasonable expectation for you. 74 on a good day maybe 72 or 73 on average days. Anyhow, thats what I think

Steve Zuckerman

Rage:
Regarding the difference in the slip %s of your props. Most "lab" modifications include some combination of thinning, sharpening, balancing, cup reduction, and occasionally blade area reduction. All this is done in an attempt to get more RPMs, because speed generally does come with additional RPMs. My Merc lab 30" had virtually no cup and the worst slippage #s I've ever seen. I had a local guy here (Performance Propeller) add some cup to this prop and we got the slip #s down to around 17%. Still not very efficient, and attempting to carry a load in the boat made it worse.
I was able to correct a lot of this by going to the P5-X and an Imco gearcase. I consequently sold all my B-1s.
Realizing I didn't have a spare, I recently bought a stock 30" B-1, and I was really surprised to see how much cup is in these propellers when they are stock. I haven't run it, but I suspect the slip #s will be MUCH lower than the lab version. It may not be all that fast either, because the blades are thick, the leading edge is relatively dull, and these props do have blade to blade imbalances, as cast. If it tests anywhere near passable stock from a performance standpoint, I'll have Matt blueprint it, but this time we'll leave the cup in it to compensate for the high XD on my boat. Who knows, we may get a B-1 prop to work on my boat yet.
To make a long story short, I think you'll find your stock 26" B-1 has a lot more cup than the lab 28", and that is why the 28" has such a high slip%. This can be corrected by taking it to a knowledgable propeller service and gradually having cup added back to the propeller, until your slip #s come down.
The objective is to get your slip #s down, without killing your RPMs. It can be done.
Regards,
Steve

bobl

Rage... My experience has shown most Rages will have around 11-12% actual slip. Any slip less than that should raise a flag as to the validity of the data. As I said before don't base your boats performance on magazine tests. They are quite often BS. The slip numbers you posted even prove the speeds are not correct. What we are offering you on this board is real world information. So, from what all others have said and what I've personally experienced a 25 Rage with 496HO will run a best of 73-75 GPS at sea level under good conditions. In most normal boating conditions you'll run several MPH less than that, maybe not even breaking 70. No one has asked the question, but how are you trimming your boat? The Rage likes a lot of positive trim. I would expect a little more than 68 out of your boat, but no where near what you are expecting. I know of several Rage's running over 600 HP that run low 80's.

Bob

Rage

Steve,

Well this is another jump along my learning curve. Thanks for taking the time to explain all the changes that are included in a labbed prop and why. I knew about most of them but definitely not the reduction in cup and the reason why. In fairness to the prop shop that labbed my 28P Bravo1, when I shared my slip results they said to send it back and they would add some cup to reduce the slip. It now obviously makes sense and I will definitely do this.

Actually my focus has been what seems to me to be a GENERALLY higher slip with my Rage than other Rages with the same equipment including prop and test conditions. What do think is the reason why in the 2001 Power Boat Mag test of the essentially identical Nordic Rage to mine with a labbed 26P Bravo1 which should have more slip than a stock 26P Bravo1 had ~3% slip and my stock 26P Bravo1 has 14% slip at the same 5000 rpms @WOT? Also at 4500 rpms the 2001 test had 8% and mine 11%.

Thanks!

Rage

Bob,

Thanks again for your real world input. At WOT I trim out until I start to drop in mph then reduce and increase trim in small increments looking for max mph. This usually works out to ~3/4+/- trim out. With the labbed 28P Bravo1 I am around 5000 rpm with light load so I do not have an issue with the rev limiter. It takes a while for the boat to achieve its max mph for the conditions.

The 73-75mph GPS max under best conditions for the Rage at sea level you mention, is that at the lightest load, say one person and low gas? Do you recall the prop, pitch and if labbed or not that gave this max top end at sea level?

Thanks!

Steve Zuckerman

Rage,
There are labs, and labs. Actually, Mercury has an "off the shelf" lab job that is, in most cases, substantially faster than the same pitch stock propeller. That's what was on my boat when I bought it. The former owner was dissapointed with all the money he'd spent, because the off the shelf lab job wasn't anywhere correct for his/my boat. As soon as I looked as the prop, I told him that's what Mercury normally does if you just order a stock lab job, and that the prop needed additional modifications, certainly cup. I thought some cup would fix all my problems, man was I wrong. It did help.
Correctly "labbing" a prop involves taking accurate speed, RPM, temperature, altitude, humididty, load, and water condition measurements, and passing that data along to someone who is hopefully familiar with the boat your working on, because they ALL have quirks. Matt and Julie have an excellent form they want filled out before they start grinding, for instance.
That attention to detail, along with a databse of propeller styles, brands, blade #s, etc. will normally yield the best results. To be fair to Mercury, I'm sure they could have done a better job of tuning my old B-1, had the former owner or I taken the time to work with them further on it. Many prop shops, like yours, will usually include one or two modifications on their original lab jobs, because this isn't an exact science.
My point is, that a correctly labbed propeller should actually slip less than a stock propeller, AND be faster too.
If you are a manufacturer sending one your boats to a magazine for their evaluation, you aren't going to send a slug.
Even then, many manufacturers are going to get "optimistic" reviews, particularly those with big advertising budgets .....................so don't be surprised that your boat doesn't run like the ones in Powerboat or Hor Boat.
Check out the article in the Oct. 2005 Hot Boat on the Heat mid cabin. The reviewers were very positive regarding build quality and styling, as they should be. These are great boats.
This boat was powered with the new 625HP V-10 Viper motor. Certainly, no slug.
Nordic says the boat will run 86MPH "under ideal conditions".
I don't know what "ideal conditions" mean to Nordic, probably running on fumes with a skilled driver in ideal conditions.
How fast did the test boat run? 76.6. That is right in line with what 600HP in a Heat runs. Mine ran 76 with a stock 575. I've seen 86 ONE time with all the work I've done, and certainly can't replicate that # 99% of the time. Load a boat up with coolers, people, and gas, there goes those "magic #s". So I think you see how those "test" results can be favorably skewed and hard to replicate.
"there are lies, damn lies, and statistics"
Regards,
Steve

Rage

Steve (and Bob),

OK you convinced me. I can let the Power Boat Mag test results on the Rages go.

Absorbing what you and others have said about props/pitch slip/labbed/etc. let me run this by you. It seems as though the sweet spot for the Rage with a 425hp 496HO is generally a 26P Bravo1. Also, as you say, the boat mfg's will submit an optimized set up for a boat test in addition to the favorable bias that they will likely receive in the published analysis. Both the 2001 and the 2003 tests were with a 26P Bravo1. The 2001 test prop was labbed by a local Lake Havasu prop shop. The purpose of the 2003 test was a comparison between stock and supercharged set up in the 496HO Rage and the prop was only identified as 26P Bravo1 so it may have been stock or modified. The 2003 test boat was allegedly off the lot of Semper Marine in AZ which would imply a stock prop but who knows.

Based on my 68mph @5000 rpms at WOT and 14% slip with the stock 26P Bravo1 the prop shop said that I should go with a labbed 28P Bravo1 if I wanted better top end. Maybe that was the wrong direction. Maybe I should be working with dialing in a labbed 26P Bravo1 instead of a labbed 28P Bravo1. What do you think are the chances that this is a better road?

Steve Zuckerman

[QUOTE=Rage]Steve (and Bob),

OK you convinced me. I can let the Power Boat Mag test results on the Rages go.

Absorbing what you and others have said about props/pitch slip/labbed/etc. let me run this by you. It seems as though the sweet spot for the Rage with a 425hp 496HO is generally a 26P Bravo1. Also, as you say, the boat mfg's will submit an optimized set up for a boat test in addition to the favorable bias that they will likely receive in the published analysis. Both the 2001 and the 2003 tests were with a 26P Bravo1. The 2001 test prop was labbed by a local Lake Havasu prop shop. The purpose of the 2003 test was a comparison between stock and supercharged set up in the 496HO Rage and the prop was only identified as 26P Bravo1 so it may have been stock or modified. The 2003 test boat was allegedly off the lot of Semper Marine in AZ which would imply a stock prop but who knows.

Based on my 68mph @5000 rpms at WOT and 14% slip with the stock 26P Bravo1 the prop shop said that I should go with a labbed 28P Bravo1 if I wanted better top end. Maybe that was the wrong direction. Maybe I should be working with dialing in a labbed 26P Bravo1 instead of a labbed 28P Bravo1. What do you think are the chances that this is a better road?[/QUOTE
Rage:
Work with Matt and Julie here. They are the experts. I have purchased propellers from many different manufacturers, OEM and aftermarket, and used several different propeller services.
It always seems to me that there are 1 or 2 guys that have the hot setup for a given hull and engine, or racing class.
I used to race outboards and can tell you exactly where to go to get whatever you need (acelleration/top end/etc.) for a racing or HP outboard. My experience with offshore type I/Os is much more limited. I have only owned 2 of them. I just went to the people who were recommended to me here on this board (by BOBL and Dave), and mentioned favorably by some race teams, Throttle Up. They seem to be the go to guys for these boats.
I am impressed with their knowledge, products, and results. I am sure there are plenty of other good "prop grinders" out there for these boats, maybe some in your area.
I'm sticking with Throttle Up. The Heat is one of the harder I/O boats to set up properly IMHO, and they made it work.
Regards,
Steve

Rage

Thanks Steve, always appreciated!