posted 01-15-2008 01:39 AM ET (US)        

BP tests have been around a LONG LONG time. I cant find a reference to the History. The man who built my Tug and set me up in buisness comes from a Family that has been Towboating since the late 1800's. I believe he said the BP tests originated in the Steamboat days. He implied performance data was too easy to manipulate for billing purposes so the US Dept of Commerce uses BP tests to set Towing Rates...be it a Tug, ski boat (Uhh Jim, is there any similarity between a Commercial Tug Boat and a Recreational Ski boat? of course there is) or canoe.

And here I am. I dont buy all this recreational WOT performance data to be accurate although I truely believe you are unbiased and trying your damndest to zero it in. Thanks again. Your efforts have potential to save the members who repower a ton of money.

I am shopping for a new engine with the most amount of torque or horsepower using the least amount of fuel. Seeking recreational POWER, I have learned a max HP engine the transom will allow and lowest gears gives me the best opportunity to do this. How do I really find out if a 60 hp Etec is more powerfull than a 60 hp Big Foot? Numbers can be manipulated. Both have the same gears and HP rating. I want to bypass the self promoting OEM data and simply hook em up to a Bollard pull test using the same exact prop on both tests and see who wins.

US Dept of Commerce using this method implies, you cant cheat, you cant manipulate the numbers. What you see is what you get.

I would like to see BP test results of a 150 hp Etec against a 150 hp Merc Optimax with floscan metering installed in the fuel line. Both seem to be awesome engines. No clue who would win. Do you agree the bollard pull test will reveal a undeniable winner without regards to data?

posted 01-15-2008 09:16 AM ET (US)            

A great deal of criticism was directed at Bombardier for using this test. It seemed to enrage many boaters. The test clearly demonstrated that the E-TEC engine produced considerably more bollard pull force than the competitor's engine, so much more that it pulled the competitor's engine's boat under water and swamped it. Yet, very knowledgeable and highly respected recreational boaters tried to pooh-pooh this bollard pull test as a "stunt" that had no value to them.

posted 01-17-2008 05:54 PM ET (US)            

Although other conditions are important I have only included
the few which are never done for these outboard tests.

In the last discussion of these tests in a recent contentious
thread, several tests presented and they showed opposite results. I found it increadable that an engineer said that a
test done ONE time was valid. Later different tests were presented that refuted the first one.

posted 01-18-2008 03:25 PM ET (US)            

Forget about my Tug stuff, I also own 4 sport boats.

I know pulling a skier or wakeboard is hard for a Great Lakes guy to comprehend.
hehe.

At the Portland Boat Show, I would say the ratio between fish boats and ski boats was about 2 to 1. Would anyone here advise me to use the same engine/gears/prop for fishing purposes as skiing (pulling) purposes with the same hull?

CW references conclude using the max HP allowed by OEM transom/hull specs results in better fuel/power/performance than underpowering will.

Regarding gears and prop options, as Tom says, "it depends". CW offers scientific data, references, expert advice and debate on figuring out the best setups.
Try to put all that aside for now and consider a bollard pull test.

The only scientific data that is required with a BP test is the depth of the water, the length of the towline and certified calibration of the pull scale. BP testing involves huge Tugs, outboards are relatively very small, the same test could be applied to a outboard inside a tank.

A BP test does not care what props they use. I WANT OEM to apply the best prop they can muster for these conditions (a dead pull).

BP TEST:

Install a fuel flow meter, hook em up, PULL.
What's goin on at various ranges of RPMs?
This isnt subjective data, you are looking at X amount of fuel being used while pulling Y pounds at Z rpms.
BPHP = max achievable HP using certified BP test methods.

The results of this bollard pull test matter to me because I will promptly run out and buy the engine that has the most pull using the least amount of fuel. Most likely the custom prop they use will be useless for general recreational purposes. So, I will get back on this site and use Jims data AND solicit prop experts knowledge/experiance to try to figure out which prop is best suited to apply to my hull factors & needs.

outa time. mk

posted 01-18-2008 11:44 PM ET (US)            

I read about this in Hunt For Red October. They had to be careful not to pour too much coal to the propeller or there would be cavitation and noise.

posted 01-19-2008 12:41 AM ET (US)            

I would be happy to discuss static pull tests if you would be kind enough to start a topic.

;-)
busy weekend ahead.

posted 01-19-2008 12:54 AM ET (US)            

Mike,

You're not making any sense at all here. Perhaps I am misunderstanding what you are talking about. Let's try this ab initio.

posted 01-19-2008 01:10 AM ET (US)            

A valid test in our boating world does not require multiple tests, certified instrumentation, et. al. But everything MUST be equal except for the device being tested AND be done with reasonably accurate (to within 1 - 5%, but not nessecarily certified traceable to the National Bureau of Standards) measurements and analyses of those results. Certainly, multiple tests will give multiple answers - but if done with reasonably accurate instrumentation and everything being "equal" - the results of a single test would be acceptable and valid for our purposes.

posted 01-19-2008 07:31 AM ET (US)            

Bartender, bring us a round please.
Gotta tell ya, A guy and his wife were having trouble getting the "urge" at the same time. So they go see the Doctor and the Doctor recommends...

Going any further would ruin our G rating.
cheers. Nobody has every confused me with being a math expert.

Jerry. Well said. Thanks. I understand the basic inertia factors involved with fwd propulsion.

Tom
http://www.nobledenton.com/guidelines/0021-5.pdf

In a BP test, the prop doesnt matter, in fact, the engine doesnt either.
The bollard pull scale will reveal how much pulling power the propulsion plant has.

Focused on OB testing,
Jim mentions cavitation issues on a dead pull. Ive towed docks, walkways, float houses & big logs with a single general use alum prop 20 hp outboard alum skiff many times. Ive found there is very little prop cavitation...if not the opposite. The engine does not achieve the rpms it does running lite.

Jerry mentions planing, well, how far has the hull lifted the engine out of the water at planing speed? How many threads involve lifting or dropping the engine a hole or two or trim out for speed, trim in for power? On a dead pull, using transom tow eyes or BW CPD tow bits, usually the engine does not lift high enough to grab air.

I am very impressed with all of the OEM outboard "boat tests." A guy can get real close to figuring out which engine/prop combo is best suited to repower. I am not debating that data, I am only debating whether or not a BP test is relevant. As Jerry and other experts say and CW performance topics constantly confirm, each hull (each test) is subjective.
The odds a REPOWER application will be exactly the same as the demo's are small...but...certainly close.

Is this a friendly debate between the data experts and a "user" expert?

Am I that far off to consider a Bollard Pull test will eliminate the hull factors using a fixed amount of HP and as many props as it takes to achieve the best results?
Is OEM "afraid" a dead pull will damage a new engine? If so, I want to know...I dont want that engine.

GRR, it hit me again. somebody stole my truck last night. If he is lucky, the cops will catch him before I do.

mk

posted 01-19-2008 11:38 AM ET (US)            

I'm sorry your truck was stolen, really I am. But I asked a simple question. What is a bollard pull test? It would be nice if you could have provided a simple answer. A paragraph or two about what that means and how it is applicable to Boston Whalers and the outboards that power them. This is your thread after all and it serves you to explain what you are talking about.

I do not appreciate being given a link to some source of information elsewhere, especially since this other location is not a specific answer to my simple question but a boring document that one needs to dig thorough to find the relevant information. At the very least, wouldn't it have been nice to point out the pertinent sections of said document?

I have answered questions here for what, six years? Thousands of replies with highly accurate, specific, spot-on technical information. Is it too much to expect a simple answer to a simple question in return once in a while?

Let me save the rest of you the trouble of reading the above referenced document and try to explain what a bollard pull test is:

A vessel is tied to a fixed point, like a bollard. The engine(s) are operated for a period of time, say five or ten minutes at a specific engine speed like "Maximum Continuous Rating MCR" of the engine(s). (What is the MCR of my Mercury outboards, anyway?) the maximum pull is measured in tonnes. The pitch of the propeller may be varied, the speed of the engines may be varied.

That's it. It is measurement of pull force with the boat tied to a fixed object.

How on earth can anybody claim that the propeller(s) and the engine(s) don't matter? The propeller(s) and engine(s) have EVERYTHING to do with it!

But more to the point: How is this relevant to Boston Whalers? The whole point of our boats is motion. Tying it to a bollard is not what our boats are used for. No propeller that is good at propelling a Boston Whaler at 30 MPH is going to be good at providing the maximum pull on a fixed object. The lower pitch prop with greater blade area will, but that is of no use to us. So I have to ask again:

posted 01-19-2008 06:09 PM ET (US)            

quote:

---

I googled "static pull test" and could not find anthing that would confirm you would get the same results using a static test as you would BOLLARD PULL TEST.

---

A bollard pull test is a static pull test. You tie the boat to something that won't move (e.g., a bollard) and pull on it. The boat does not move, it is static. You measure the amount of pull.

There is no reason to start another topic to discuss static pull tests because that is the generic name for a "Bollard pull test." You don't really have to use a bollard. You can tie the boat to anything that won't move.

My engine has enough power to spin my propeller up to 6,000-RPM. Can you explain why it won't have that power if the boat is tied to a bollard? How does the motor know that it is tied to a bollard and should lose power?

As for cavitation, in non-static testing, the propeller advances into clean water, but in a static test the propeller cannot advance. The propeller keeps turning in the same place. There is no advance. Clean water has to flow into the propeller, instead of the propeller simply advancing into clean water. I am certain that this will create an entirely different situation for the propeller. The angle of attack of the blades will change, the performance of the propeller will change.

posted 01-21-2008 12:41 AM ET (US)            

hehe.

Again, I am seeking simple test info that confirms Brand X engine will PULL the hardest using the least amount of fuel. WOT is covered.

I'll be back another time when things settle down.

posted 01-23-2008 11:58 AM ET (US)            

Does anyone have a link for this. I'd like to see the video.

posted 01-24-2008 02:22 AM ET (US)            

As mentioned by others a Bollard Pull for a recreation boat is not a good measure of the engine performance/spec within the recreational boat. (Bollard pull test for a docking tug boat or workboat, sure that is what it is designed to do, push massive things slowly. You will often find controllable pitch propellers (CPP’s), Z-drives, or Voith drives to accommodate for low speed high pull conditions. -- If my recreational whaler can pull an aircraft carrier at 2 knots that’s great, but if it can’t get on a plane, what’s the point.)

For a straight engine comparison I suggest that “brake horsepower” would be the measure of performance. Brake Horsepower (bhp) is the torque/power delivered at the shaft as measured by a dynamometer at certain RPM’s. (This removes propeller performance and the gear set can be accommodated for; which is a huge part of the overall boat/engine performance.)

Looking at a different marine industry: With marine diesel engines there are ISO standards the control the test conditions of these performance tests (such as air temp, ambient barometric pressure, humidity, etc). All most all diesel engine manufactures subsequently show: bhp versus RPM, fuel consumption versus RPM, and shaft torque versus RPM. These are the tools you would use when deciding on engines and selecting a ropeller for the vessel (a big deal). Outboard engine manufactures aren’t so forthcoming with this info at times, but it’s out there.

But as most of us know from looking at a performance curves of 2-stroke and 4-stroke engines there is a large difference in mid range torque capability (and thus bhp) and fuel economy. (Hence the swamped Yamaha in the video.) -- Hooking an engine to a dynamometer (calculating the effect of the gear set) and measuring the fuel flow is something that can be done in the shop and the results will be reasonable.

posted 01-24-2008 05:36 AM ET (US)            

I have performed this etec test MANY TIMES with Tugs in reverse.
Instead of bollard pull, we go nose to nose and somebody says go. Having nearly equal HP, the engine that will come up to turns the quickest or a teeny tiny head start will win every time. A Bollard or Static pull test is different because you can measure the pull and fuel consumption at any RPM. Again, use the same wheels Etec and Yamaha used.

I also refer my interest in BP or static testing to a couple of Etec owners who were able to diagnose their RPM curves over fairly long periods and I found it interesting their % of WOT was very small compared to CRUISING RPMS and IDLING.

I am learning and thick headed but Ive been around boats a long time.
I understand setting up the right prop & HP with the boat "depends" on many things...I am trying to remove the "depends" issue PRIOR to spending $15k on NEW ENGINE repower options. Thanks all for helping.

Stolen truck update:
Perp is still out there. 2003 F-350 Lariat LE (short box dually 50k miles) is totalled. Insured.
Too many assets = too many liabilities.
Garage sale forthcoming.