Disconnecting Engine Linkage

[Chip Hindes]

My experience has been the same as Dan and Catigale, which is what I've been saying all along. I've sailed with the motor up, then down, then up then down, for literally hours, on all points of sail, in all wind conditions, and have proved to my satisfaction beyond a reasonable doubt, that for my boat and motor, with the motor in neutral, there simply is no measurable difference. This is not only with the GPS, which I admit does have built-in averaging, but also with my paddle wheel speedo. Since the resolution of both these digital devices is 0.1 knots, an increase or decrease of 0.1 knots is pretty much in the noise.

As I said, I sail with the motor up primarily based on the fact that I know there's slightly less drag, even if I can't measure it. But it's also on principle, just like pulling in the fenders: it's what sailors do.

[Terry]

Interestingly, with only a couple exceptions, it seems that owners discern no noticeable difference yet owners do notice a difference. Could it be that hull and design differences attribute to the more subtle nuances that owners experience or is it the blue hull factor. I have tried both last summer and steering was exceptionally improved with the engine disconnected and raised. Steering was also improved with the engine down and connected but the improvement was moreso with the engine disconnected and raised. I also noticed a 1/2 - 1 mph gain in speed with the engine raised, but I also noticed better stability with the engine down. I believe my experience reflects the logic of physics and not my imagination. If I was racing anther Mac I would not hesitate to raise the engine for the extra gain, given that I was forgetful enough to not have raised it yet or had it down for other reasons. I find it hard to fathom that some folks actually believe that there is no difference when the laws of physics imply that there is a difference, go figure....

[DLT]

I don't think anyone is implying that there is absolutely zero difference. Rather, I think we all acknowledge that there must be some. You can't stick something in the water without "some" drag...

What we are disagreeing about is how much difference... Chip says that any difference is in the 0.1 knot noise, which sort of agrees with Moe's suggestion that the difference is basicially measured in tenths of knots.

I have seen a difference on the GPS. While I haven't run extensive tests, the difference has been in the tenths. But, I, personally, have no problem loosing those tenths, whether in the noise or not, for the peace of mind and smooth steering that I get with it down...

To others, that difference down in the noise is still important enough to raise the motor, if only on principle.

I wouldn't be surprised to see more difference on M's as opposed to X's. Not that I'm one of Rogers flock, but he does claim a less turbulent wake on the M. If that is so, then we should expect to see more difference in M's...

Again, though, you gotta ask yourself whether the difference is meaningful to you... If you think it might be, then try it both ways, on your own boat...

And yes, if I were somehow to find myself in a racing situation, I'd probably raise the motor... But, then again, I might just start it...

[Moe]

Let me once again add that because I don't trust myself to remember I've tilted the motor up, I remove the key from the ignition before tilting up. In fact, we never put the key in the switch when the motor is up. It's a reminder that will hopefully prevent us from running the impeller dry and damaging it.

[Chip Hindes]

I find it hard to fathom that some folks actually believe that there is no difference when the laws of physics imply that there is a difference, go figure....

Nobody said there is no difference, they only said the difference is so small as to be not measurable by means at our disposal. I'm fairly familiar with the laws of physics you cite, I've done some of these calculations in the past, and I can assure you the calculated difference will support my numbers, not yours.

So, what is not fathomable to me is how a 2-3% reduction in frontal and wetted area which occurs when you put the motor up can result in a >20% imcrease in speed.

[Frank C]

... As I said, I sail with the motor up ... on principle, just like pulling in the fenders: it's what sailors do.

Gotta agree with this ... it's the main reason for me too.

... If I was racing anther Mac I would not hesitate to raise the engine for the extra gain ...

Also, gotta figure he's otherwise going to assume you cheating!

[Chip Hindes]

... remove the key from the ignition before tilting up. In fact, we never put the key in the switch when the motor is up. It's a reminder that will hopefully prevent us from running the impeller dry and damaging it.

OK, it's true confession time. I confess, I leave the key in the ignition at all times. I further confess, I have started the motor while it was tilted up, on perhaps 5 or 6 occasions over the five years I've owned the boat (since new). I still further confess, I once got myself into such an emergency state of mind that started the motor while tilted up and then left it running the entire seven or eight seconds it took to tilt it down. When it's warm the motor starts in less than a full revolution; a fraction of a second of cranking and it's running. There's nothing quite like the rap of a good sized two stroke running with the prop out of the water.

Here's why:

Because of the cable routing, my ignition switch is located on the bottom of the motor control, right side of the X pedestal facing downward at around mid calf height. I'm not particularly happy with it, but this is the way the original Havencraft did all their Tohatsu installations. The dust/water cover over the key slot spins freely, independently of the "correct" key orientation and can easily get misaligned with the actual switch when the key is out. It is quite a large PITA to get the key in the right orientation that it slides right into the switch on the first try. On occasion is has taken me more than 30 seconds to get it in right; before I learned how to do it by feel, twice I actually had to, in effect, stand on my head so I could see the cover and turn it to the correct orintation to allow the key to be inserted. At night, it's well nigh impossible.

So, when we're not tied at the dock the key stays in the switch for safety reasons.

Now, the tilt switch doesn't work with the key in the "off" position, and several times I've inadvertantly turned it to start when all I wanted was the ability to operate the tilt switch. I've also turned it to start when it was already running and I really wanted to shut it off. Remember, it's upside down so turning it in the correct direction is not intuitive. So, I normally leave the key in the "on" position at all times for tilt control, and shut the motor off by pushing the safety lanyard switch button.

But here's the kicker (pun intended); the key to the whole dissertation: Since delivery in Sep '00 I have never voluntarily replaced the impeller. It was finally "replaced" this fall along with the entire lower unit as a result of damage due to an accident. I'm sorry I didn't insist on seeing the old impeller, so the only thing I can testify to is that there was never any overheating, no reduced flow at the peehole, nor any other indication that the impeller was anything other than 100%. To top it off, after the accident but before the repair, this summer I went to Bimini and back with a bent prop shaft and that nasty old, run-dry-several-times impeller. No problem, Mon.

YMMV. This is not something I recommend. I'm only citing my experience to the fact that running a dry impeller for a few seconds is not necessarily akin to falling off a cliff or jumping out of an airlplane without a 'chute.

[Terry]

Chip wrote:

the difference is so small as to be not measurable by means at our disposal.

Strange, Both my GPs and paddle wheel device detected an instant 1/2 mph gain, beyond that may be attributed to other variables or perhaps a continual increase from a raised skeg, can't say for sure, but the means I had at my disposal registered an increase in speed the minute the skeg was raised. The skeg and 4 blade prop do create drag, perhaps it is just moreso in my case. In stronger winds I don't mind leaving it down for more stability and the drag is likely not as much concern as heeling is. Still, I stand by my results that were measured with two means at my disposal, results that were measureable in more than single tenths.

As for starting the engine while raised, well, I confess I'm guilty on two occasions, but the extra noise incurred by the engine is like an emergency alarm going off, key gets switched off in a heartbeat, and the scare pretty much makes it harder to forget in the future. My tilt works with the ignition off and key removed, no big deal but I have had a few occasions where I forgot to change the quick pin and reconnect the engine, most irksome to say the least.

Chip, my name is Terry, "Kermie" is the name of my boat, my wife collects frogs, I nick named her "Mrs. Kermie" after Kermit the frog and named the boat after her.

On edit:
Chip also wrote

I've done some of these calculations in the past, and I can assure you the calculated difference will support my numbers, not yours.

I wonder how many engineers and inventors throughout history discovered differences between real world results and classroom calculations.

[Frank C]

Chip wrote:

the difference is so small as to be not measurable by means at our disposal.

Strange, Both my GPs and paddle wheel device detected an instant 1/2 mph gain, beyond that may be attributed to other variables or perhaps a continual increase from a raised skeg, can't say for sure, but the means I had at my disposal registered an increase in speed the minute the skeg was raised.

Terry,
Neither Chip nor I recognize any significant difference, both X boats. You note a very significant difference in your M. It's easily concieveable that your earlier observation is THE answer ... the M hull reflects a much more significant demerit when dragging her outboard - not terribly surprising - means you're both right.

Just read Roger's Puffery - " ... much inherent drag in the X-boat's CB trunk and transom ... ," so that the motor makes little additional difference. Maybe it's not all "Puff."

[Chip Hindes]

I wonder how many engineers and inventors throughout history discovered differences between real world results and classroom calculations.

Probably a lot fewer than discovered their calculations were correctly validated by experimental results. Also, a lot fewer than the number who learned that anecdotal reports of results that contradict a simple calculation by a wide margin are to be treated with skepticism. This isn't rocket science and we're not breaking new ground here. These effects are quite well known and understood.

Exceptions to the rule normally have an explanation as well. By my experience about 90% of the time, it's that the experiment was fundamentally flawed and all the variables were not properly accounted for.

Not sure what to make of Frank's point. If we were to believe Roger Mac's most recent "puffery" as Frank puts it, we'd have to conclude that the combination of daggerboard and rotating mast make the M blindingly faster than the X, but other than a hull of a lot of smoke and flame on this board, I don't see the results of actual contests validating that supposition; if it exists at all, the improvement is quite modest. Could we suppose that the flow past the X CB trunk was so screwed up that by the time it hits the motor it makes no difference, while the M flow past the DB is pristine until competely trashed by the motor? Possible, but still doubtful. If it were so, we have reports of M's putting their motors up and running away from X's like they'd lit the afterburners. Not seen that at all; the only boats I've seen that could do that were 26D's.

I should point out as well it's not only M owners who report significant differences. A fair number of X owners have reported similarly large numbers as well.

Sorry about the "Kermie". No disrespect intended; I was replying to the signature; didn't notice that the name was different.

[They Theirs]

Motor Boat Propeller

The Drag of the Motor Boat Propeller is like dragging a bucket. Even the PHRF allows credit for boats possessing three-blade, specially designed with smaller blades, sailboat fixed blade propellers over those with feathering propellers. They also state these credits do not offset enough for the drag of these fixed propellers and also state the loss can very well amount to 50 seconds per mile over the feathered propellers. The fact that small boats suffer more from the drag of the fixed blade propeller than one proportional on a larger craft. (Can you imagine the Big Footprint of extreme oversize lower units of the biggest of these outboard maxi 3 and 4 blade motorboat propellers)?

Macs dont have a strut or fixed propeller in the water, as this is strictly a choice of the captain. If you want to drag a flat blade shovel at this point I cannot see any reason to convince you otherwise. For that matter, why not attach a rope and try throwing out a bucket and a couple of sea anchors to prove your boats are beyond any loses incurred by one and all, and of coarse while dragging a lower end and the huge blades of your outboard motorboat propeller and engine connected to your rudder steering.

For me, Im disconnecting the steering coupling and tilting my engine up to enjoy the benefits of sailing faster and better without the drag some seem to fancy.

[Terry]

Frank wrote:

Terry,
Neither Chip nor I recognize any significant difference, both X boats. You note a very significant difference in your M. It's easily concieveable that your earlier observation is THE answer ... the M hull reflects a much more significant demerit when dragging her outboard - not terribly surprising - means you're both right.

Just read Roger's Puffery - " ... much inherent drag in the X-boat's CB trunk and transom ... ," so that the motor makes little additional difference. Maybe it's not all "Puff."

Nice olive branch Frank, much obliged.
Chip wrote:

Could we suppose that the flow past the X CB trunk was so screwed up that by the time it hits the motor it makes no difference, while the M flow past the DB is pristine until competely trashed by the motor?

Chip, I find this very acceptable and whole heartedly agree, it supports another point you made:

Exceptions to the rule normally have an explanation as well. By my experience about 90% of the time, it's that the experiment was fundamentally flawed and all the variables were not properly accounted for.

Cheers!

[Chip Hindes]

The Drag of the Motor Boat Propeller is like dragging a bucket.

You can say this as many times as you wish. That doesn't make it so. You can say the drag of a centerboard is like dragging a tree trunk. Both statements are equally wrong.

[They Theirs]

Chip

As Don Adams used to say: "Sorry about that, Chief." And "Would you believe. . .?"

From "Offshore Cruising Encyclopedia"

For displacement speed, large, slow-turning props are much more efficient than smaller, fast-turning props. But large props take more space underwater and exert unbelievable amounts of drag when you're sailing.

[delevi]

Quite the controversy!
For those who do disconnect and don't use BWY's system, what do you use? I believe their system only works on a handful of engines, the Etec probably not being one of them.

I simply removed the bolt and nut from the bracket and replaced it with a hitch pin. The process is about 15 seconds to disconnect or reconnect. The problems is that the bolt and nut hold a rubber stopper (on the nut) which prevents the tiller tube from crushing the protective little cap around the opening in the transom for the tiller tube. Now I have the bolt back, after having the cover replaced and some patchwork done to the gelcoat around the opening, along with various steering adjustments and replacing the wheel break (unrelated.) Im sort of stuck with the bolt now, but certainly don't want to use tools if I choose to disconnect the iron genny. I like being able to reconnect in a hurry, and the thought of dropping tools in the water.... well you get the picture.

I think the consensus, for the most part is to leave the engine down in heavy weather, but tilting it up would be beneficial in lighter air, at least on an or just out of principal Chip & Frank, I know you tilt up (out of principal,) but do you disconnect? Frank you mentioned you dont and dont feel much of a difference in the helm. I feel a lot of difference. feels crapy. The helm is very heavy, even with the relatively light 230 lb Etec. Chip, what about you? Rick, I see you rigged the BWY system on your Yamaha. Jim, I can't see what engine you have but you use the system too. Was it plug & play or did you have to tweak anything? Terry & Aya, I'm curious to know what your setups are for disconnecting. Basically, any ideas on an easy disconnect setup that wont trash the side of the transom