MacGregorSailors.com

Yea, I'm about petering out on this one as well...although I think there are still a couple counter punches coming my way.

I will say that I do have the highest respect for both Moe and Chip and I have learned a ton of things from both of them on this board....but one last comment (jab) since perhaps I got a bit personal here:

Moe wrote: Since this is basic high-school physics, that's the only educational qualification one needs. And you don't even need my 44 years of working on and hot-rodding engines. There are many with only a few years experience who understand this, and some even went the vo-tech route and didn't take physics in high-school.

I have no doubt that you are probably one of the world's top mechanics, not only because you have a super comprehensive view of the "how" but also a pretty decent grasp of the "why" which puts you way above the average mechanic and more into the realm of mechanical engineer. I try to focus not only on that...but also on the "why not" part which is why I tend to be a bit outspoken (ok, my Greek heritage also has something to do with it too) and question things alot. I certainly understand, that there are plenty of super successful people who never went to college, and conversely, many total failures with college degrees (my BIL's for example..lol). Decades ago, the difference between graduating HS (or vo tech) and graduating college seemed to be that after HS, you thought that you knew everything, whereas after college, you realize that there is still a hull of a lot more to learn. Maybe things are a bit different these days as I hear that the general ability in (some) universities has gone way down lately. And frankly, some college professors are total assh*les anyway..usually when they have forgotten what it is like to learn..because they end up "teaching" all the time.

Anyway, that is a bit of who I am...if I had my druthers, I would be an astro physics guy trying to disprove/enhance Einstein's theories like Hawking, but alas, life is short, and you end up doing what you can make the most money at.

So to make up for that void, I come here and argue with you guys instead... I'm pretty sure that all of us take it in good debate spirit and end up leaving a little wiser than we were...I know I do.

Moe wrote:Trying to pull a fat girl up slalom one time doesn't break an outboard crank.

What about a fat cat on two skis?

Besides. What about the fat cat??

If I tied my boat to a tree on shore then went full throttle, my boat would remain in place. Would the outboard blow up? If so, how long would it take to blow up? Would it be independant of prop size?

Moe, you are mixing good technical details in with preposterous theories. Do you really expect to prove or have anyone believe that HP (force) and wear and tear actually go down with a ballasted boat....both running at WOT (and with the same prop)? We are going around in circles again, but let me just restate: higher fuel consuption at lower RPM with ballasted boat = more energy used, hence more wear and tear.

I thought it was quite a stretch even saying they were the same, but I was almost buying that...except for the fuel consumption and induction noise part! Going back to the original thread, does this mean that BK can now actually buy a smaller engine to power around with full ballast? (rhetorical question, please don't answer)

I tried to offer you an olive branch, but you don't want to budge an inch on your theories, so I can't argue with you anymore.

Maybe you should go fly a constant speed airplane around for a bit so that you can understand that it is not all about RPM..and that load does factor heavily into this equation...or see how much fuel you burn with your engine at 6000 RPM in neutral. Better yet, go tie your boat up to a dock (or tow a 100 ton barge around) and run it at WOT for a few weeks and then report back to Mark.

P.S. - Appropriate graphics Mark (wonder how long you have been waiting to use the cat on skis one!). And as far as head banging, this thread is getting almost as bad as politics! We may as well agree to disagree.

Dimitri-2000X-Tampa wrote:Moe, you are mixing good technical details in with preposterous theories. Do you really expect to prove or have anyone believe that HP (force) and wear and tear actually go down with a ballasted boat....both running at WOT (and with the same prop)? We are going around in circles again, but let me just restate:

As I said before, only the guy who put the motor on the dyno at WOT knows whether horsepower at 5300 is less than or equal to the horsepower at 5900 rpm. While there is a good possibility it is the same, it is also likely it is less.

Read my prevous post carefully... I said the wear attributable to rpm goes down at lower rpm. Relative to the higher rpm unballasted condition, wear attributable to torque (combustion pressure) will go up, since in the peak rpm range, torque is falling as rpm increases. The end result is dependent on the rate of torque change relative to the rpm change.

Dimitri wrote: higher fuel consuption at lower RPM with ballasted boat = more energy used, hence more wear and tear.

Is that the logic (more energy used) that you use to determine the engine is putting out more horsepower at WOT and a lower rpm ballasted than at WOT and a higher rpm unballasted? If you use a fuel flow meter, you should find the fuel used at WOT, whether ballasted or not, is roughly the same. That won't be the case at part-throttle where you are adjusting the throttle to achieve the same rpm or boat speed. In this case, fuel use will be higher when ballasted.

Dimitri wrote: I thought it was quite a stretch even saying they were the same, but I was almost buying that...except for the fuel consumption and induction noise part! Going back to the original thread, does this mean that BK can now actually buy a smaller engine to power around with full ballast? (rhetorical question, please don't answer)

Okay, I won't answer that question.

Dimitri wrote: I tried to offer you an olive branch, but you don't want to budge an inch on your theories, so I can't argue with you anymore.

Whew!

Dimitri wrote: Maybe you should go fly a constant speed airplane around for a bit so that you can understand that it is not all about RPM..and that load does factor heavily into this equation...

I spent several years in aircraft maintenance and never heard of a constant speed airplane. Did you mean an airplane at a constant speed? If you want to move the discussion to weight and balance, and calculated fuel loads, I'll try to dig out my books on that. (no, I won't really... let's not go there).

Dimitri wrote: or see how much fuel you burn with your engine at 6000 RPM in neutral.

In the old days, this wouldn't be much fuel because the engine would grenade pretty quickly. These days, the calculations would be messed up because the rev-limiter would be turning the fuel or ignition (carbed motors) on and off to keep revs down. In fact, on some outboards, that would occur at a very low rpm if in neutral.

Dimitri wrote: Better yet, go tie your boat up to a dock (or tow a 100 ton barge around) and run it at WOT for a few weeks and then report back to Mark.

P.S. - Appropriate graphics Mark (wonder how long you have been waiting to use the cat on skis one!). And as far as head banging, this thread is getting almost as bad as politics! We may as well agree to disagree.

I will agree that we disagree, and try to come up with some catchy phrase like Duane did with "faster than hull speed." I understand now why he did! Now I don't know this for a fact, but I would suggest BK look at one of those 90HP Tohatsu's if he wants to make sure his MacGregor will plane.

--
Moe (duckin' and runnin')

PS I think we all deserve a pat on the back for keeping this debate civil.

Mark, your questions are easy. I understand those kind.

If I tied my boat to a tree on shore then went full throttle, my boat would remain in place. Would the outboard blow up? If so, how long would it take to blow up? Would it be independant of prop size?

Your engine will not blow for 6 years because it has a Suzuki warranty and everybody knows things don't break until after the warranty period. If the rear cleats hold, and if the lines are equal length, and if the ballast is empty, and if the boat is unloaded (and a few more ifs) and you apply full throttle with your big engine, the bow will probably rise and the stern sink flooding the engine. We use to bet on these things.

I hope it's not a long winter for these guys.

Back before I got remarried, I went to a biker party held by some people I didn't know. All was fine until some guy brought an old car, wired the throttle wide-open and started a pool on how long the engine would last after started. The car ran so poorly it wouldn't get anywhere near max rpm, and just ran, and ran, and ran. People started demanding their money back, and the guy started saying that would be too hard to do, etc. The crowd started getting ugly, and then someone drove the old car into the (big) bonfire, where it stalled. At that point, I got the hull outta there most hurriedly. Never did hear if the car blew up or how the owner fared.

--
Moe

Does all of this still apply to a blue hull

Holy ****, the beat goes on.

You gear heads should understand is that there are educated arts and letters types here about that dont understand what youre talking about.

There are different inclinations, layers of talent and intelligence.

However, the physics we ding bat letter types only comprehend is observable.

For instance, taking the little punkie out to the huge splinter filled teeter totter. Punkie gets placed on the end holding on for dear life to the handle bars. Dad gets way up toward the fulcrum and up and down we go and punkie doesnt get tossed up into the sky. Theres probably a formula for this.

Dimitri is fighting an up the stairs battle with swords twinging, flaming lanterns swinging.

Moe is patiently trying to explain. Dimitri is insulted swinging his sword more violently. Moe shakes his head and advances with a long pole with a point on the end.

If I was younger, I would print your stuff, fold it up and put it in my rear pocket.

Moe is convincing with his experience and tools. Dimitri is convincing with his background and observation.

Dinks, like me, have only their observation. I can only adhere to Dimitris argument about a smoking motor trying to push the pier onto the shore. Load, or what have you, on the prop generated up through the gears to the pistons.

However, Chip and Moe agree on Dimitris conclusion, and only disagree on how he got there. And how he might have got there, I havent a clue.

I like the part about Moe abandoning a biker rally before the car exploded. I mean, you figure this guy's been around?

Wow,
Talk about taking an uncomplicated issue and making it complicated! No wonder my wife hates History channel's "Modern marvels"! Physics really has nothing to do with engine wear. It all come down to how hard the engine is running (low vs. max capacity/torque). Speed and rpms are all irrelevant. An engine either runs at or near its maximum horsepower or not, regardless of the weight of the "load" it is pushing. If it is a heavy load, you go slower, if it is lighter load - faster. The engine wears at exactly the same rate, WOT-higher wear, Low throttle - lower wear. One of the reasons I got the 90 tohatsu -- go faster at lower rpm = lower engine wear. Hope I don't get any "college test day nitemares" after muddling thru all that.
Rolf

Dad, Can I go play in the puddle.........

It is only with greatest restraint I have stayed out of this one......lol....
[ON EDIT --Oops, as I check back on the first page of this thread...I already traipsed through-OFF EDIT]

Saw about 17 places to hop back in on this thread.......but As I like to only bring clarity, math, and repeatable metrics to the issues..... lol...., as well as good craftsmanship and occasional indepth analysis.....

and lest I fail to leave in time before the car explodes...heheheh

I must remember that we must only use our powers for good.......'Ommm Mani Padmi Ommmm'

keep the faith Brothers!! (And Sisters)

You all tried!!

(now let me put my gag back on........... I know I know.. some of you wish I hadnt taken it off............... )

Billy wrote:Mark, your questions are easy. (and a few more ifs) and you apply full throttle with your big engine, the bow will probably rise and the stern sink flooding the engine. We use to bet on these things.

Why, I'd bet that'd depend on the angle you set the motor trim at.

Vectors and scalars.

Trimmed all the way up, I'd bet you'd be correct and the stern would sink; however, based on off hand physics, if the motor were trimmed all the way down, the stern would not sink enough to flood the engine. One more thing, shouldn't we take into consideration the amount of weight in the bow and stern?

One more thing, shouldn't we take into consideration the amount of weight in the bow and stern?

Yes, Mark. Another one of those ifs I was talking about, but I was going to leave Dimitri's childhood friend out of this. (She has probably evolved into a swan anyway.)

If I used all this thought, research, standards, etc. when I did my mods years ago, I'd still be thinking and saying it wouldn't work. I like just using a little common sense, then bolt and go. I try to remember the Titanic was built by engineers and such and the Ark was built by amatuers. That way when I screw up, I can always say I didn't know any better.

Well, I tried really hard to stay out of this thread for a while anyway ..

Rolf wrote:Wow,
Talk about taking an uncomplicated issue and making it complicated! No wonder my wife hates History channel's "Modern marvels"! Physics really has nothing to do with engine wear. It all come down to how hard the engine is running (low vs. max capacity/torque). Speed and rpms are all irrelevant. An engine either runs at or near its maximum horsepower or not, regardless of the weight of the "load" it is pushing. If it is a heavy load, you go slower, if it is lighter load - faster. The engine wears at exactly the same rate, WOT-higher wear, Low throttle - lower wear. One of the reasons I got the 90 tohatsu -- go faster at lower rpm = lower engine wear. Hope I don't get any "college test day nitemares" after muddling thru all that.
Rolf

Rolf, I think that is a bit oversimplified and only agree with this in a perfect world when you change your prop each time between heavy load and light load. Synergizing with one of Moe's earlier posts on the matter, my point is that in the real world, most people prop the Mac for unballasted, highest speed operation. Therefore, when we are carrying a heavy load, we are essentially over-propped and overloading the motor.

Billy wrote:Yes, Mark. Another one of those ifs I was talking about, but I was going to leave Dimitri's childhood friend out of this. (She has probably evolved into a swan anyway.)

Probably a filthy rich swan from what I remember (her father had a huge business empire and you would know several of the businesses if I named them). Despite her size, she could do fairly well on a windsurfer too as well as the slalom skiing.

I have two props for the Whaler, and it takes maybe two-three minutes to change them. One is for heavy loads and/or heavy seas, where throttle response can save your life, and one is for light load, lower rpm cruising on calm water. The former can result in rpm slightly above Mercury's range for WOT if lightly loaded, while the latter results in rpm below that range, so we don't use WOT with that prop, and ease up on plane.

Some people put one sail on the forestay (especially with a roller furler) and never change it. Others (especially with a hanked foresail), switch between jib and genoa to suit conditions. The prop is no different and takes no more time to change than a hanked foresail.

Our Mac came with a 13" prop on the DF50, which will be replaced with Robert's recommended Solas 3 blade 12.25 X 9" stainless. I will try the 13", and may use it, for times we won't be powering the Mac at greater than hull speed (which will be most of the time), to keep the rpms down. At the least, we'll have a spare prop, which I wouldn't go out on any small boat without (well... at least one without sails and even with them I'd rather dock under power with the spare prop than under sail).

--
Moe

Hey I haven't been on this site for a while and I can see you're still "discussing" the finer points of motor sailing! Where is that fellow Frank Mighetto? I'm sure he could add something to your debate