Ideal Prop Slip %
 

Even with my prop shaft at 4.5" below the keel of the boat (just like everyone else) my prop slip % is super low (7-8%).

Is there a magic # with respect to slip. Do I want/need to be up in the 12% range to free up the prop. I can't seem to get close to the 6100 I need to spin and it seems to make sense if I come up 1/2" or 1" it should free it up a bit.

Please throw some numbers out there. Most cats dream about 7-8%. I can't imaging a Heat with those kind of numbers.
RPM, speed, Gear ratio, Prop (and type) and work done to the prop if any.
Thanks,
Dave

0%

1.5 ratio, 6100, 89 GPS, 26 (25) Stock B1 was base # the boat came with.

1.5 ratio, 5800, 86 GPS 25 P5X in Havasu.

Standard height drive, prop is 4.5 inches below the keel of the boat. IMCO SC Xtreme (I thought I might have to much drive in the water but most everyone is about the same in terms of prop depth).

I was working down the path of the wrong gears , I.E. 1.34's because the slip actually pencils out at 12-13ish with a 1.34but I actually pulled the lower and confirmed 1.5's.

I need to spin 6100.... The boat usually runs in the 56 to 5700range with the 26.

From talking to you.... you might want to point out that you have yet to personally see the boat go over 86mph. The 89 mph figure was stated by others, but never seen by you.

5800rpm, 25 pitch prop, 86 mph = 6% slip

This seems really low.

You should also post this question over in the Prop section, and hopefully get some expert opinions.

How fast have you personally seen a 26 Bravo go? RPM? Speed?

Chris

I have a labed 28 from mercury racing that would work great on your boat. If you are at 8% slip you are doing good but some boats like slip to get the best top end numbers. Most fountains run in the 20's with slip to get the best top end speed.

I've actually run the boat 87 on Elsinor w/two people and a little over 1/4 tank.

87 @ 5850 with a box stock B1.

Once again, 6%.

Maybe I need to take a little cup out to free up the prop..
or come up a 1/2.

I don't know.

Have you checked to find out what prop was on the boat to get it to run 89 mph?

I seriously doubt it was a stock prop.

You can have the stock B1 thinned and labbed to pick up aprox 200 rpm. Or try a Mercury Racing labbed 26. It also will turn more rpm's than a stock 26 B1 while also probably being faster.

Chris

SouthOCG

Julie at Throttle-Up told me that the ideal slip for our type of hull is between 10% - 14% .
Steve Z's and BobL's slip is right around 13.5% using a P5x prop.

You might indeed need to raise your outdrive in order to increase slip and pick up speed.

Before going to that expense, I would have your current 26 Bravo thinned and blueprinted in order to increase rpm and speed. Or buy a Mercury labbed 26. Both these options are sure to increase your speed by a couple of mph.

Both these options will also increase your slip.

Chris.

On a side note, If you take the speed per horsepower on my boat, Steve Z's boat, and Bob L's boat, and plug this constant (227-229) into BAM's boat speed calculator, along with your aproximate weight of 4850#'s - 5000#'s, in addition to your 700hp. It perdicts your boat speed at between 86 and 88 MPH. Your boat speed to horsepower is right in line with everyone else. Both BobL and Steve Z have done a lot of calculations on our boats, and I find their math to be correct on my boat as well.

and
 

SouthOCG,
Altitude, weather, water conditions, and loads (people, gear, fuel) have a big effect on speeds. My boat varies up to 5 MPH from ideal conditions to bad conditions.
Do you boat at a higher altitude than the Havasu test that resulted in 89 MPH?
I assume your boat was lightly loaded during that test.
What was the weather like when they ran the test? I assume they tested in the winter to make deadlines for spring publication.
If you factor in ideal conditions, ie cool weather, light load, lower altitude than your locale, that could easily make a 3-5 MPH differential from the Hotboat test.
Have you asked Nordic to borrow that "magic" :rolleyes: prop they used for the HB test? I would.
A friend of mine owns a new 27' Lavey step vee with a 710 Ilmore, and he usually runs 87-89 here in summer heat. That boat has a much more radical double step hull than ours, and being a former drag boat racer, he's an excellent driver. I know he's squeezing everything he can out of it.
With a TU blueprinted 28" P-5X, my boat runs 90 @ 5850, 91 @ 5900, and 93 @ 6000 on the limiter. This propeller has about 13% slip, and equates to 30" Bravo 1 4 blade in performance.
I agree with Chris that your #s @ 700 HP are correct and in line with our (Bob, Dave, me) testing.
Best Regards,
Steve

My boat does a max of between 80 and 82 mph in perfect conditions at 600 hp. Using the known value of aprox 17hp per mph for our boats, with you having 100 more hp, that would put your top speed between 86 and 88 mph. I can hit between 79 and 80 most of the time. I have hit 82 once. SouthOCG's boat should be about 6 mph faster than mine.

Chris

This was all hashed out before on this boat before SouthCog owned it. I figured it would come back around on it's own :drink:
The boat obviously has 1.36 gears. Bravo One props run 1"-1.5" less pitch than advertised (per Julie) whick makes this all a further stretch of physics.
Dave

(By the way, don't forget Mr. T was driving his own marketed package down river in crisp, cool, zero humidity Parker air if my memory serves me well (which is questionable))
http://www.offshoreonly.com/forums/s...=illmor&page=2

My thoughts too Dave. It's hard to fool physics. My boat had 20% slip with a similar setup.
Steve

OK....

Just back from Havasu (boat is down there for the winter now).

For clarification.......... Postively 1.50 gears.
I pulled the lower and checked them.

I did have an opportunity to run a -1 while I was there.
The results were close to my 0.

Light load, mid 80's, little wind, 84 @ 5700.
And this is with the labbed B1 26

Took the boat in to hook it up to the computer and it turns out I have a bad IAC and a bad mass air sensor, which is reading the temp on the motor much higher which in turn is changing the curve on the computer.

Ilmor is sending out some new parts as well as a new computer. Parts will be put in next week, I on the other hand won't be back down until the middle of November so I'll work on some new numbers then.

That is awsome that you found the computer thing, and were able to try a -1 lower. Sounds like you are narrowing in on the issues.

Was the -1 worth anything in terms of handeling or otherwise?

Chris

I've got to start over after I put in the new ecm.
Once I've got some good numbers, I'll throw the -1 back on and give it a run.

I will say with the -1, the boat didn't cavitate when it rolled over. Seemed to be a little quicker 20-50 and 40-70 as well.
Didn't need as much trim and my slip was a little higher (10%).

I may run back down next week late to run it again just to see where it's at. From what Ilmor is saying, the new ecm, new iac and mass air sensor I should be able to move through the 5700 wall with ease.

If anyone wants to come and verify the #'s (because nobody seems to think they're not accurate), by all means you can meet me there and we can go for a ride. :argue:

You need a 34 with 710's or a thor then you wouldnt need to try so hard to go fast. I think a thor with a 710 would be bad ass and run way over 100mph.

This coming from the guy who is trying to sell his 525 and build a 1000hp motor.
Did I miss something somewhere?

It's no as much about going so fast as it is about getting the motor to run right/pull the right RPM's. The top end is simply a result of getting the boat to run right. How often am I going to run 90??? Probably every chance I get.

As far as a 34 with 710's..... You never know.

The Thor................... When I was in Havasu last week, I was talking to a very reputable person with "friends" at Nordic and the word is that production is coming to a halt on the Thor. Rumor has it, they're completely looking to re-tool the bottom once again because of performance issues.
That would make 4 bottoms in 4 or 5 years.
The other side of it, who's to say that anyone know's what they're talking about.

Good luck with the boat. I would get a new prop from bronson hill (bravo 1) . If I do put a new engine in the boat it will run over 120 and I will promise that. Look how flat the gen 3 bottom runs with a good driver.
http://www.youtube.com/watch?v=Xzyfi...eature=related

The cat definately looks like it is running flat and fast.... but that is very smooth water compared to what I boat on most of the time.

Chris

P.S. One of my favorite quotes...

The true measure of a man or a thing, isn't done when conditions are good, but when things or conditions are poor.

They say that the Thor has problems in flat water that is why I posted this one. The thor handles the rough better than my last boat which was a Heat with a 500efi
http://www.youtube.com/watch?v=Q7GVL7LxXvc

They are NOT going to change the bottom again! Here are some real #'s 2008 525 wood free boat 92+ mph. 2008 full CARBON/KEVLAR boat merc 700sci NXT package 112.8 MPH
We have these boats instock now! If anyone is interested in a new Nordic thor please call for the correct info. Or better yet come out and see us in person,and if iam wrong on the performance of these boat . Ill pay for your trip out!
Tim
oregoncustommarine.com

John,

Your boat is one best looking water machines I have ever seen!

Cant wait to take a ride in a Thor !

Chris

Tim,

Who's the new guy Nordic just hired to head up the some of these projects? I was told his name but can't recall off the top of my head......

Rumor has it he's shutting down the Thor line for right now until they get the bottom right. Like I said in my original post, rumors at this point all second hand info, but if I'm right?

I agree... possibly the best looking Thor I've seen.
For sure a nice ride.

The new guy is Mike L ! And your wrong! It really doesnt do anyone any good with that kinda of info.
I really dont think they can make this boat any better. Maybe a merc 1200hp and six package would be cool.
Tim
oregoncustommarine.com

I want one of those.

Thanks guys. I love all Nordic boats and cant see myself owning another brand. They take great care of there customers, and the dealers are all great also. I love my Thor just wish I had a little more like all of us do.

I might be on to something. Maybe i can get them to bld me one for the 2009 show season.

John what color's would you like to see it in. :ernaehrung004:
Tim
oregoncustommarine.com

Geezz.... I don't know, I think I would start with bagging as a start and then move from there.

The thought that the boat is a good as it can be and can't be any better is just the start of failure.....

Never rest or you're next to get passed, should be the the approach.

So are you saying thay are ?

1 changing the bottom

2 start bagging

3 no sure

Nordic is leading they way with wood free boats & and full on carbon/kevlar layups. With that being said why would you say they are changing the boat again? I posted some real # 's,and the Nordic Thor works really good.

There is always room for improvement.

:food-smiley-007:

I'm saying....

1. Rumor has it they're looking to work the bottom.

2. They don't bag.

3. no sure


If the boat stays the way it is, great.

If they change the bottom, we can all look back at this and say.. WTF, the rumor was true.

Like any vehicle company.... Chevy, Ford, Chrysler, Toyota, Nissan, etc, etc, etc

The product is changed and updated almost every year.

I see this as a good thing, and signs that progress is being made. I am sure Nordic will update all of their boats at some time.

I think that Nordic rocks, and applaud their continuing refinement.

Chris

P.S. I am sure I would love my boat even more with a 1200Sci --- Who wouldn't?

:Whatever:
call jim ie southocg for all Nordic future updates
Tim
oregoncustommarine.com

(You posted)The Thor................... When I was in Havasu last week, I was talking to a very reputable person with "friends" at Nordic and the word is that production is coming to a halt on the Thor. Rumor has it, they're completely looking to re-tool the bottom once again because of performance issues.
That would make 4 bottoms in 4 or 5 years.

Performance issues?

525 wood free boats 92mph

700 sci carbon/kevlar 112.8mph

And your point is ?

My point is.......

It's rumored that Nordic is looking to re-tool the bottom..
For what reason, I don't know.

With that being said and if it's true, F'ing good for them. At least they get the part about trying to be better/faster then the competition and not wanting to fall off the map.

Numbers are what they are and there will always be someone faster. For christ sakes, I think Howards 28V runs 92 with a 525 but at least Nordic isn't sitting on their hands looking to get their a$$ kicked.

So if they are stopping the Thor for now or looking to tool the bottom, I say good for them, they're doing the right thing and consumers should be made aware of these changes if in fact it's going to happen.

Unfortunately it may cost Nordic a couple sales now but they probably pick those up down road. Nobody wants to buy a boat and then find out 6 months down the road the next best $hit hit the block.

Not telling people about potential changes and having them find out 5 months after they just dropped a buck 40 as the new stuff starts to roll out is how you piss someone off and lose a potential repeat customer.

Kudos to Nordic even if the dealers don't want to hear it...!!

At 4.5 inches below the keel with my propshaft:

Prop slip with a 30 Bravo is at 13.4% at WOT of 5050
Prop slip with a 27 P5x is at 12.5% at WOT of 5350

Both at 80 mph +/- a few tenths

Since this is a prop slip thread........

Any thoughts?

Chris

Chris,

Thanx for getting us back on track....

As soon as I get back down to havasu and run the boat with the "fixed" ecm and iac, I'll have to start over on my numbers as everything should change.

The Real Story!
 

I would just like to add a little clarity on this whole “New Bottom” discussion! We are in-fact “re-tooling” a new bottom for the 2009 Open Bow Thor only, not the current Thor. This effort is totally focused on the NEW 2009 Open Bow Thor and the modifications are directly related to the Open Bow version, not the current Thor! At Nordic Boats we will always strive to improve all of our products, and new versions with updates will add to our quest for continues improve; this applies to the entire company, not just one model or boat design! At Nordic we will strive to build the very best 100% wood-free Performance Boats on the planet!