outboards

[dlandersson]

Make that 25 hp.

dlandersson wrote » Sat Nov 09, 2013 7:59 am

I keep re-visiting the idea of 25 mph also. A Mac 26X has a Mercury 30 mph and it seems to work fine. I'm thinking a 25 might also be enough to get me on plane - and at 25 mph, I would not need a separate policy for my boat.

Yup, 25 mph will put you on a plane pretty fast.

[mastreb]

I'm thinking a 25 might also be enough to get me on plane

25 hp will get you to 8 knots in a Mac X, nowhere near a plane. The only utility of 25hp over 15hp for a boat that size is hole-shot starting and stopping power (which is not to be discounted).

[dlandersson]

Even if I chrome everything?

I'm thinking a 25 might also be enough to get me on plane

25 hp will get you to 8 knots in a Mac X, nowhere near a plane. The only utility of 25hp over 15hp for a boat that size is hole-shot starting and stopping power (which is not to be discounted).

[Catigale]

Even if I chrome everything?

I'm thinking a 25 might also be enough to get me on plane

25 hp will get you to 8 knots in a Mac X, nowhere near a plane. The only utility of 25hp over 15hp for a boat that size is hole-shot starting and stopping power (which is not to be discounted).

Nice!!

Matt and I saw some hole shots last night in SAN....

[Ixneigh]

I have an etech 60. I consider it, or any motor, a mission-critical item on the Mac M because of its marginal sailing ability. I have sailed all my life. I love my M but it is NOT a keelboat. Just the way it is. I use the xd100 oil, and had the engine serviced last week by a local mobile shop. He told me that the 3 year service interval is pretty much bunk and suggested a 2 year service interval for my type of use. Water pump, plugs, compression check, gear oil etc. The engine has been fine so far, but will just barely get the boat on plane, at around 15 knots. I do have 350 lbs extra ballast in the form of lead in the bottom, and another 400 lbs of gas water and personal items. Fine. Close to the advertised 21 knots but one knot less for every 100 pounds of junk on the boat. because we hardly ever have flat calm where I am, I hardly ever run it full out on plane because I dont want to get drenched with saltwater. If I ever need another engine, I may consider the 25 FS Honda.

Why dont they make an oil recirculating two stroke? Wouldnt that solve all the problems? If the etech is point lubricated why not collect the oil and pump it back into the oil tank?
Ix

[mastreb]

The engine has been fine so far, but will just barely get the boat on plane, at around 15 knots.

Are you running ballast in? If so, this is the right speed. Dump ballast and you'll get to 17 knots, if not something is wrong. What prop and what is your tach reported WOT RPM?

Why don't they make an oil recirculating two stroke? Wouldn't that solve all the problems? If the ETEC is point lubricated why not collect the oil and pump it back into the oil tank?
Ix

Because there's no reason to do so.

In a two stroke, the valving arrangement that creates the power every-other-stroke phenomenon requires that some oil remain inside the combustion chamber when the gasoline is injected, and that oil gets flamed off when the gasoline detonates. So losing some oil is unavoidable. Read the wikipedia article on two strokes and imagine how you'd keep a wet-sump oil area separate from the combustion chamber, and you'll see the problem.

Now, with a direct-injection motor like the ETEC (but not a traditional two stroke), you could technically have a separate wet-sump separated from the combustion chamber, and while you'd have to oil both, you could have two separate oiling systems, one which flamed off in the chamber like a two stroke, and one which operated like a 4-stroke with a wet sump where the oil is "permanent" and would have to have periodic oil changes.

But given that you must burn oil anyway, why not cycle all the oil through through the combustion chamber so you've always got "new" oil in the motor?

This begs the question: Why do we change oil?

It's not because the oil gets "dirty". It's also not because the oil collect metal shavings from the engine as it wears. While both of those are true, neither of them are why oil degrades and neither of them would build up fast enough to require frequent oil changes.

What makes oil "oily" (high viscosity and low coefficient of friction) is the fact that oil is made of very long molecular chains of hydrocarbons. They are basically simple hydrocarbon molecules attached end-to-end that create very long chains. The longer the molecular chain, the more lubricative that particular molecule is. Think of them like molecular bearings: The longer they are, the more likely it is that a part will slide all the way along them without hitting anything else. As they get short, the part has to "hit" a lot of different ones as it goes by, each "hit" increasing friction, which increases heat and the probability of strike damage.

Natural crude oil is a collection of various random lengths of chains. Refiners separate crude oil by distilling it at different heats, and they measure the viscosity to create different grades of oil. These viscosities map to an "average" molecular chain length, but the fact is that all natural oils contain a lot of short chains, medium chains, and long chains.

Synthetics are created with all long chains. So they're not a random blend, all the molecules are long.

When you run you engine, these molecular chains are cleaved (cut in pieces) by the mechanical motion of the engine. Think about that: Your engine is slicing up oil molecules as it runs. The long chains get cleaved into medium chains, and the medium chains get cleaved into short chains. The effect is that as you run your engine, the oil becomes more and more "watery", i.e. having lower viscosity and less of a lubricating effect.

This is why synthetic oils last far longer than natural oils: Because all the chains start out long, it takes much more cleaving to get them all to short. Starting with random chains, even at the same measured viscosity, results in a more short chains faster.

XD-100 is extremely long-chain synthetic oil, along with some other detergents. That's what makes it different than TC-W3, which is typically natural oil. Because it's all long-chain, Evinrude knows it will last longer so they can direct-inject less of it.

So, when you run your engine, you're breaking down your oil period. With a two-stroke, you have the >opportunity< to blow that broken down oil out the exhaust port rather than keeping it and breaking it down further. Since the owner has to dump new oil in anyway, why not just blow it all out?

The ETEC (and other prototype designs now being considered for alcohol-based engines achieve their emissions compliance in two ways):

1) Direct fuel injection eliminates the phase where new air/gas is pushed into the cylinder while the exhaust port is open. In traditional two-strokes, the new air/gas was use to to push out the previous stroke's exhaust, and this meant that some unburnt fuel/oil mix would go out with the exhaust. That's >horrible< for emissions. With a direct fuel injection, they pump in clean air to push out the exhaust, and then inject gasoline after the cylinder has moved past the exhaust port closing it.

2) By directly injecting oil only when necessary and only where necessary, a feat they accomplish using heat sensors and precision injectors, they can minimize (but not eliminate) the amount of oil that winds up being combusted. Long chain oil is much harder to completely burn than short-chain gasoline, so you want to have as little as possible of it in your combustion chamber. It's required for lubrication on the stroke however, so you have to have some.

At WOT the amount of oil burned in an ETEC at combustion is about the same as an old-fashioned two-stroke (1 part oil to 100 parts gasoline), but at idle it's dramatically lower (something like 1:300) because much less heat is generated at low speed. This is why you'll always see the ETEC's emissions reported as being super awesome at IDLE, but they don't talk so much about its emissions at WOT.

When all is said and done, the ETEC emissions are much lower at idle than a modern four stroke, but probably a bit higher at WOT. In all, they're about equal.

[March]

Very informative entry, Mastreb. Thank you, that makes a lot of sense

[bartmac]

25 hp will get you to 8 knots in a Mac X, nowhere near a plane. The only utility of 25hp over 15hp for a boat that size is hole-shot starting and stopping power (which is not to be discounted).

Probably anything beyond 10hp is a waste....we fitted a 15hp Suzuki 4 stroke cw high thrust prop and anywhere above about 1/3 revs is not making a difference speed wise and having had a myriad of other trailersailers of similar size all fitted with 9.9hp seems to enforce the hull speed argument...if you don't have the hp to plane that's it speed wise

[Catigale]

Thanks bartmac, I've been looking for that 15 HP datapoint...

The only other thing I would like to know is what the smallest motor than make way (2 knots) against a 5 knot current?

I did manage to make 1.4 against 4 at Westport MA with. 4HP 4 stroke but I steered the boat with the motor due to the slow speed...helm was very sluggish

[seahouse]

Why dont they make an oil recirculating two stroke? Wouldnt that solve all the problems? If the etech is point lubricated why not collect the oil and pump it back into the oil tank?
Ix

Hey Ix –

Good question, and that is, in fact, what happens in the E-tec engine. The surplus oil gets collected and is pumped back and recirculated in the engine, just like the dry sump in a race car engine.

XD-100 oil has the advantages that all synthetics have – among them it has a higher flash point. That means that the thin film that is left behind by the oil control piston rings flashes off, or is burned, at a slower rate. So it stays longer in the microscopic nooks and crannies (rough texture) manufactured into the cylinder walls and does its magic for a longer time before having to be replaced by fresh oil. (Smoothe cylinder walls = bad; if anyone hasn't heard that old story- just ask ).

Of course, 4 strokes burn oil in this same way as well, but the 4 stroke's upper cylinders are separate and closed off to the oil in the crankcase, and 2 strokes, by their design pumping through the crank case to the combustion chamber, necessarily cannot be.

Regarding oil (my take - if you aren't technical in nature, you can skip the rest of this post ) -

The base oil stock does not break down in an engine, in fact the base oil will last more than the life span of an engine. That is the basis of the oil recycling industry – the base stock is very stable and long-lasting, so that is what is separated from the rest of the broken down additives and impurities, a new additive package is mixed in, and it's put back on the shelf for sale as recycled oil.

In the early 90's I worked for a company that used considerable amounts of oil, both collected from machine leakage and gear and crank case changing. It was collected in 45 gallon drums (some might call them 55 US gallons) a company took them away, and returned with “new oil”; recycled, cleaned, and with a new additive package. With the same base oil. And mixed in with that of other customers.

“Multigrade” (like in your car) engine oil is a thin oil that has had thickeners (viscosity {index} improvers, VI's) added to it so that it doesn't thin out at higher temperatures and lose its lubricity. It's the thickeners (and other components, pH buffers- the “base number”, dispersants, detergents, anti-oxidants etc) in the additive package that break down allowing the oil to thin, that's a major limit to the life span of oil in a modern engine. I'm guessing that is what you're thinking of in your post above, Mastreb, the VI's?

The VI's, are long molecules, the longer they are, the higher the viscosity of the oil they are in (thicker). Note that the actual oil molecules themselves are, in fact, short relative to the VI molecules. At lower temperatures VI's take on an amorphous shape, balled up and therefore short, so the oil behaves as if it were thin, such as when you want it to flow freely during a cold engine startup.

But as the temperature rises the cross-linking bonds release and the molecule becomes longer, thus increasing the viscosity of the oil, and preventing the oil from thinning out and losing its lubricating properties. The long molecules of the VI's do break down from shear in time and become shorter; the oil thins. So as the oil gets older, especially in high horsepower engines, the additive package becomes depleted and the oil thins.

It's important to know that the additive package is not oil and does not contribute to lubrication, quite the opposite. The more additives are mixed in, the more the oil and it's lubricating properties become diluted. Except with synthetic oils.

The beauty of synthetics is that they can be built from scratch to both flow easily at cold temperatures, and to not thin out at high temperatures, without any, or much fewer, additives than conventional mineral oil. Synthetics are actually multiple classes of oils that can be custom tailored to the needed properties, so they haven't been “diluted” with additives to the extent that mineral oils have.

One thing is for sure - oils just keep getting better and better.

Hope this might clarify things a wee bit. If not... ask.

- Brian.

[mastreb]

Brian's explanation is more complete than mine: It is the viscosity improvers (mostly polymer waxes) in traditional oil that break down due to mechanical shearing far more than the natural mineral oil. They break down as described in my post. Unfortunately, natural mineral oil is not a great lubricant without VI's--they're present in all mineral motor oils.

Synthetic oils are made with from scratch with the molecular chain formations (mostly branching chains) that are required to get the lubrication properties desired without any viscosity improvers, and because they don't have the viscosity improvers which break down and cause thinning of the oil, they last longer.

I've never before heard the assertion that the hydrocarbon oils don't break down at all, however--even synthetics have to be changed periodically, and if they weren't breaking down oil, one would assume that oil filters could handle removing impurities without changing the oil out completely. In fact even the best Group IV base stock synthetics only triple the oil change period for a car.

In any case, full group IV synthetics like XD-100 last longer and smoke less than multigrade oils like TCW3 (a lot of the smoke is the ash of the viscosity improvers rather than the oil itself).

By the way, when you look at oils for your car, they're divided into four groups:

Group I & II: Mineral oil blends with viscosity improvers
Group III: Ultra-high quality refined mineral oil legally allowed to be advertised as synthetic
Group IV: Created from scratch using the FT Process, otherwise known as "Fully synthetic"

Most Synthetics, like Castrol GTX, Mobil1, and Valvoline SynPower are blends of Group III and IV and are not truly full synthetic. This matters little, because you change the oil in a four stroke anyway.

At the end of the day, I'm sticking with the TCW3 because it's available at fuel docks and because a two-stroke burns its oil long before it could possibly break down anyway. I'd hate to be locked into an oil I use a lot of (one quart per 24 gallons if you plane) and have to mail order.

[kadet]

The base oil stock does not break down in an engine, in fact the base oil will last more than the life span of an engine. That is the basis of the oil recycling industry – the base stock is very stable and long-lasting, so that is what is separated from the rest of the broken down additives and impurities, a new additive package is mixed in, and it's put back on the shelf for sale as recycled oil.

Actually not that simple, oil in an engine gets oxidised and breaks down molecularly with heat apart from absorbing water and other contaminates that are harmful to the lubrication process. This is a chemical not a mechanical process.

Every 10°C doubles oxidation and in fact most engine oil only has a relatively short shelf-life and should be used within 3 years if stored at 20°C. Modern synthetic oils are a lot more stable an in general should last twice as long but they still eventually succumb. This is also the reason oil changes are recommended at a time as well a mileage limit by engine/oil manufacturers.

Recycled oil is actually re-refined by being heated to very high temperatures and subject to high pressure to fuse hydrogen atoms at the molecular level to restore the hydrocarbon value it is basically newly refined oil again, and depending on the refining process it can be turned into not just motor oil but hydrologic fluid, automatic transmission fluid or just about any other lubricant as required.

If the base oil lasted forever all you would need to do is change your filter and put in a fresh additive package but this is not the case.

[RobertB]

By the way, when you look at oils for your car, they're divided into four groups:

Group I & II: Mineral oil blends with viscosity improvers
Group III: Ultra-high quality refined mineral oil legally allowed to be advertised as synthetic
Group IV: Created from scratch using the FT Process, otherwise known as "Fully synthetic"
Most Synthetics, like Castrol GTX, Mobil1, and Valvoline SynPower are blends of Group III and IV and are not truly full synthetic. This matters little, because you change the oil in a four stroke anyway.
At the end of the day, I'm sticking with the TCW3 because it's available at fuel docks and because a two-stroke burns its oil long before it could possibly break down anyway. I'd hate to be locked into an oil I use a lot of (one quart per 24 gallons if you plane) and have to mail order.

Notice you pointed out that Castrol is not Group IV. Recommend you look into the 0W30 and 5W40. These are different from the rest of the lineup, in fact they are one of the few synthetic oils that meet the ACEA A3 rating. Castro does not advertise what the base-stock of the oil is but is suspected that these two oils are indeed Group IV (research Bobistheoilguy.com. Look for "Green Castrol," previously the 0W30 was green - it has quite a cult following).

Back a long time ago, a representative from the Oil institute of America (I think) gave a lecture at Texas A&M (where a co-worker went to school). One of the takeaways is that the durability of an oil is how long the carbon chains are. Oil is general from two geological locations - coastal/ocean and mid continent. Mid continent oil has longer carbon chains and by the way, Castrol oil is refined from mid continent oil (at least back in the 1980s). I believe today, one of the differentiators that makes synthetic oil special is the uniformity of the carbon chains/molecules. Personally, I am not concerned at all on what the base stock is, just what the final product is. I side with the courts on this one.

[seahouse]

The difference in the term "synthetic" as it is allowed to be put on the bottle is that it is considered a marketing term, as opposed to the use of the term as it is more accurately used by others to describe its chemistry. For the average application under normal conditions, such as in a standard automobile, the conditions are not severe enough that the difference will be noticed, so the use of the term synthetic is close enough (just like in horseshoes and hand grenades) . Using an oil with the suitable API certification label should keep you protected.

The difference becomes significant outside of normal operating conditions, such as found in turbo chargers, or motorcycles, or high temperatures, or very low temperatures (Canada). Or even if you happen to run without oil! If you are into any of these categories, and want that extra protection only a true synthetic (by the chemist's definition) can give, then the label on the bottle is not of much help in finding that product.

It's also not helpful that the court ruling made it legal for the oil companies to label a product as being of a higher quality than it really is, and charge a much higher price for a product that is only slightly more expensive for them to produce. You get less bang for your buck when you unwittingly purchase these products.

The court ruling was a loss for consumers, and a huge gain for big oil. It has led to a big mess because now you have to do a lot of research, and the info you get needs to be current because the formulas are changed regularly, so you're shooting at a constantly-moving target.

If the base oil lasted forever all you would need to do is change your filter and put in a fresh additive package but this is not the case.

And yet that is what this company did; the oil collected, recycled and returned was done by a relatively small company that did not have access to the massive cracking towers and other hugely costly oil refinery equipment. They collected and cleaned the oil, tested and renewed the additive package for hydraulic oil. If this oil were not performing up to spec, over the years this high-production equipment would have ground to a halt. It hasn't. I think that mastreb's assertion that the breakdown of the long molecule chains into shorter ones as a mechanical process, while it might seem simple, is accurate to what happens at the molecular level, and is one of several breakdown processes.

The future just might see the base oil retained, filtered, cleaned, and additive package renewed in some applications. That might even be the case now with stationary engines and ships. Oil made for diesel engines has a more durable additive package that greatly extends oil change intervals because the base oil lives on.

It's certainly safe to say the base stock will not last forever, no one here has said that, but the key point in our thread is that it is the additive package that breaks down long before the base stock oil does, and that is the most common motivation for changing your oil.

The whole premise of shortening of the molecules with stress makes me think of the similarities to apoptosis; which results from the progressive shortening of the telomeres on the end of (our) DNA strands. As DNA replication continues the telomeres get shorter and shorter from a number of influences and stressors, until finally they're so short that the cell (or we) die of old age or disease. But we can't simply renew ourselves by figuratively changing our oil. Quite yet.

[kadet]

They collected and cleaned the oil, tested and renewed the additive package for hydraulic oil.

An oil subjected to high temperature and pressure as part of it's usage, so it was probably possible because it is re-refined as part of it's use. Very different from what is going on in an engine.

A Synthetic oil is produced by combining or building individual units into a unified molecular structure. Pure Synthetic base stocks are are man-made and tailored to have a controlled molecular structure with predictable properties. Mineral base oils, which are complex mixtures of naturally occurring hydrocarbons.

However petroleum products can also be synthesised into a unified molecular structure so are they not also synthetic?

At the end of the day who care where the raw material comes from as long it performs the same.