DaySailer on Long Island Sound: outboard thoughts?

[Afelgate]

I recently bought my friend's DS1 which we've sailed together the last few years. The boat is in great shape, but it's time for a few upgrades, and I would like to get the community's thoughts on sizing an outboard.

I'm based in Clinton, CT and sail on Long Island Sound. The area has tides, currents, and even waves (though not really big ones). The DS came with an electric trolling motor which just isn't powerful enough. Multiple times, I've had to fight my way back to the dock against the tide and/or current and haven't made headway. This is a safety issue, as I regularly take out friends and want my little boy to be able to join us too. Waiting for the tide to turn isn't an option - especially if a storm kicks up.

The factors I'm considering in choosing an outboard are power, weight, and length. I'm not considering used 2-strokes; safety and reliability are the overriding concerns (besides, I paid $500 for the DS & trailer so can afford to splurge on the engine I would really welcome feedback from folks sailing on Long Island Sound in particular, or ocean conditions in general.

O'Day recommends a long shaft, so unless anyone can convince me otherwise I'm going with that. Power is a little trickier. Some folks on this forum and others seem to think 2.5hp will be adequate. I'm skeptical for my conditions - and adequate isn't good enough in this case. I need to have power in reserve in case we ever need it. I'm thinking a minimum of 3.5hp would be better; but how much do I really need?

Weight, of course, is the other part of the equation. How much will start to impact sailing performance? Typically there will be two adults in the boat, 400 lbs max total. Add in a couple of kids and maybe we'll be pushing 600 lbs. Factoring in an outboard, will an additional 30 lbs on the transom be a problem? How about 40, or 60 (the largest outboard I would consider @6hp)?

My inclination - if no one at all has any feedback on this post, which I hope isn't the case! - would be to go with a 3.5hp 4-stroke Nissan long shaft weighing in at 43 lbs. But like I said, I'd like to hear what you all think.

Thanks in advance for any and all feedback.

Alan
DS1 #10236

[Alan]

As someone who's paddled for dear life on San Francisco Bay when a tanker somehow didn't get the memo from Vessel Control that a swim race we were escorting was coming through, I'd suggest that on Long Island Sound you consider run-for-it speed above all.

[K.C. Walker]

I sail on Long Island sound, specifically Fishers Island sound. I use an older Johnson 4 hp, long shaft, two-stroke that weighs 30 pounds. I never open it up all the way, so I feel that it has plenty of reserve power. I wish that I didn't have that much weight on the transom but don't feel that it's much of a problem for cruising. I think a long shaft is good for a transom mounted sailboat motor, in that if you walk forward, it does not cavitate.

In Stonington we have more current out in the Sound but we don't have as much tide fluctuation, so we don't have as much current in the harbors as you do. I have had no problems with current plus fighting a headwind.

I don't know what the exact sweet spot for a DaySailer would be horsepower wise. Unless you modify the transom you're not going to get enough power to make the boat plane, nor would you want the weight penalty to do so. So, 4 hp is more than enough to maintain hull speed. Until you get enough horsepower to plane (I would guess 20+ hp) anything more than 4 hp would be a waste.

This is a long way of saying that the 3.5 hp Tohatsu is probably a good compromise between weight and power to fight the current. Though, the little Honda weighs less and might be enough power. Tim Webb just picked up a small Honda, upgrading from trolling motor, and he might chime in on whether he thinks it's enough.

[jeadstx]

I think the specs on the Day Sailer recommend a motor from 3 to 7 HP. I have a 2.5 HP motor.

John

[seandwyer]

Alan,

I understand what you mean about wanting to be sure you can get out of the way or where you need to be in an emergency. I use a Mercury 3.3 and I have never felt like I needed more power, or, that even if I had more power that it would have been of any use. I feel like the shape and size of the DS is such that anything in that 2.5 to 4 HP is plenty.

That said, what I have had some problems with (at the most inopportune time) is flooding and, once, dirty fuel that caused the motor to keep stalling. Motors costing what they do, I have no intentions of buying a new one, but have often thought that if I did I might look into one of the Lehr propane outboards. There's no potential for flooding or getting tainted fuel and there's no chance of spilling fuel. The motors don't even have a choke. From what I have heard they are very simple and very reliable and there's far less danger or mess (spilled fuel etc). You can buy a large fuel tank, or use one of the Coleman sized propane canisters--one lasts about two hours on the smaller engine. I should say that I don't know anyone that has one and have never used one myself, but someone on here was talking about them about a year ago and maybe with a little coaxing they will come forward. Worth looking into.
http://golehr.com/lehr-marine/

[Alan]

Sean,

I suppose it depends on what sort of vessel traffic there is in a given sailing area. When I read "Long Island Sound" I immediately thought of big ships. It sounds like K.C. has peaceful water to sail in, so maybe I was overly worried.

My Torqeedo, which claims to be the equivalent of a 3 hp gas motor, moved my heavy DSII at 5.6 mph the one time I tried a speed run (indicated on the motor's GPS). That would indicate that 3.5 hp is enough, at least for normal wind and current. And a gas motor wouldn't have the Torqeedo's problem, which is a drastic reduction in range when you use full throttle.

I think a Lehr propane motor would be ideal in most circumstances. I really like the idea of the screw-on canisters - easy to change out when you need a refill, compact and easy to store, and relatively safe. The only reason it wouldn't work for me is that my two local reservoirs are electric only.

[seandwyer]

Hey, Alan,

Sorry--I think I wrote my response in a rather confusing manner. I was actually addressing the guy that started this thread--his name is also Alan. As for what you said about paddling--I completely understand. I'm not in that lake much, but I have had to move out of the way fast a few times in Lake Erie for a freighter and once a large ferry. Also, the chop can be pretty tough to get through at times. But when it's all said and done my motor always seemed to be more than enough--I've never had to open it up, but when I did I didn't really notice an increase in speed which makes me wonder if there is a limit to how fast the DS can go being pushed. I'm sure a larger engine could make it go faster, especially a larger prop, but the weight would probably be too much for the transom etc.

Come to think of it, from some of the reading I have been doing lately about guys that buy a transom mounted outboard to replace a defunct diesel inboard, a lot of thought seems to lean towards bigger props being more effective. They say that although a diesel runs much slower, having a bigger prop pushes better than a faster rotating outboard with a smaller prop. Me, well, I don't know. I used a motor once last year and am shooting for not even once this year--but if I take a trip to Erie, the motor is coming with!

[TIM WEBB]

So far, I've found the Honda 2 to be more than adequate, WAY better than the old 45# troller, even against some pretty strong headwinds. Haven't had to deal w/ much tide or current tho. I replaced the carb and fuel line/filter, and am religious about only running fresh, non-ethanol fuel through it. With the motor mount I built, the short shaft is fine (cav plate is a good 5-6 inches below water level).

The 2.5 that jeadstx has is a Lehr motor. If I was buying new, I'd definitely go that route ...

[GreenLake]

@seandwyer - you asked "is there a limit on how fast a DS can be pushed?"

The answer two that is "yes". The limit is called the hull speed and depends on the property of the medium (water) and the geometry (length) of the boat. The value (in knots) is something like 1.34 times the square root of the waterline length in feet, or just a touch over 5 knt for a 16' DS.

Right around that speed, the force needed to "push" the boat increases steeply with speed, so opening up your outboard has seemingly no effect. The curve doesn't go to infinity, so with sufficient power (>10hp?) you will leave the regimen that is described by that curve ("displacement" and enter first "forced mode" and then "planing". Initially, planing takes less power than forced mode, but as you go (much) faster the resistance increases again. If your boat is loaded, the power to get through forced mode is higher, by the way, making it less likely for you to get to planing, but the speed at which those transitions happen is unchanged.

The reason for the simple formula for hull speed has to do with the physics of water, less with the details of your boat.

Surface waves in water move faster, the longer their wavelength is. That's why tsunamis travel so fast. In reverse, if you create a wave at a fixed speed (bow and stern wave) it gets longer as you move faster. At some point crests and troughs will be separated just far enough that the bow will continually be climbing a wave crest while the stern squats in the trough. That's the hull speed, and given by the formula above.

To get a boat like the DS to plane under sails, it helps to get a temporary boost from a wave or gust and to steer for maximum speed until the boat is on the plane (after that, less power is required to maintain the plane).

Hull shape (other than length) does not change the hull speed, but it does influence the nature of the transition to planing (and how easy it is for the hull to plane). There are some modern skiffs that have hulls that no longer have a discernible forced mode. They transition smoothly from displacement mode to planing. It probably doesn't hurt that they are lighter as well.

Because of the limitations of hull speed, once your outboard can push the DS to about 5kts, getting a larger outboard will not provide much benefits - other than if you need to motor into a building gale - at that point, any additional horse power might come in handy to overcome the additional wind resistance.

Finally, it matters what propeller you fix on your outboard. At full revs your outboard may turn so fast that the "screw" that a standard propeller describes through the water may be moving at a much faster rate forward than the 5 knots that you can push your DS. That means, the propeller is constantly slipping. It's just churning the water. If you match the propeller to your max speed then it would be more efficient. (If your outboard is oversized, then you'd be trying to match not the max revs, but whatever intermediate value corresponds to 5knt motion).

[Afelgate]

Thanks so much for all of your feedback... this is really helpful.

I'm definitely intrigued by the Lehr 2.5hp propane outboard. I'm liking the quiet, simple, reliable operation. Reviews seem positive.

But I'm wondering if 2.5hp would be enough power. Specifically, would moving up to 3.5hp make that much of a difference? I know anything will be stronger than my current trolling engine, so if 2.5hp can move the DS in most conditions, then I'm good with that.

One other concern: the Lehr 2.5hp is only available in a short-shaft version. O'Day themselves recommend a long-shaft. But are there (not overly complex) ways to address this?

John - since you have the Lehr 2.5hp yourself, have you found this to be adequate? Where do you sail, and in what conditions?

K.C. - you're in Stonington, what are your thoughts? Great to hear from a local guy!

[TIM WEBB]

If you clamp the motor to the transom, you probably want the long shaft. If you are using some sort of motor mount that allows the motor to sit lower, the short shaft will be fine.

[GreenLake]

@afelgate - if 2.5 hp gets the DS to hull speed (or near hull speed), going to 3.5hp will not make it go appreciably faster; that's because the power required to add that extra fractional knot goes up so quickly near hull speed.

In an earlier post @Alan reported that he reached 5.6 mph (not knts). This compares to 6.2 mph for theoretical hull speed. His motor was a nominal 3HP electric outboard. Torqeedo uses a propeller that's well matched for those speeds, so you might need a 3.5HP to get to the same speed he reached, if it uses a standard prop. Allowing for some uncertainties in the power ratings and estimates there's a good chance that the 2.5HP would get you to at at least 5mph, especially if fitted with a thrust propeller. That would mean, the last HP would get you only an additional .5 mph.

If you motor against a 3knt current, both motors would give you nearly the same speed over ground (a bit over 2knt), because hull speed limits the speed through water.

However, if you occasionally motor against strong winds, a 3.5HP may, in that scenario, have the advantage of being able to overcome the added wind resistance, where the 2.5HP would perhaps not be able to maintain the same speed. However, keep in mind, that wind resistance does go up with the square of the wind velocity, so once you get to the point where your progress is limited by wind resistance, you'd need to double your additional engine power for every 40% increase in wind speed.

Which should convince you that even with a larger motor, your DS won't be a good vessel to take out into a gale

All of this points to that 2.5HP is going to be sufficient power in a wide range of applications, and conversely, that pretty much anything above 3.5HP starts being unnecessary, because you can't make the DS move any faster (except in a frontal gale).

I don't mix (too) much with traffic where I sail but I do sail in currents. I've managed, so far, to work around the limitation of the trolling motor I use, which perhaps rates 1HP?, so I can't conceive of where I would put to use 2.5HP, let alone 3.5HP. Both seem more than plenty from my perspective. But, it's your decision.

[K.C. Walker]

We all wish that we could do without auxiliary power. So each motor already has one strike against it. I think the general consensus here is that 2 hp is adequate and 4 hp is more than adequate. I think your three choices are the three that I would consider if buying new.

They are all going to be noisy, though the Honda is a little bit noisier. They are all going to be a little heavy, but the Honda is a little lighter.

The Lehr has the positive of no gasoline, but you will want a motor bracket for the short shaft. Also, outboard motors generally last for decades so a good track record and solid service and parts network is important. These motors are new with an unknown track record. The Honda and the Tohatsu have a very strong parts and service network and good durability reputation.

You might want to check the current in Clinton Harbor to see what you are actually dealing with.

Also, you should join us in Fairhaven for the New England DaySailer meet up!

[jeadstx]

My 2.5 hp motor is not a long shaft and works with the transom. The cavitation plate sits just below the water. Originally I was going to put a motor mount on, but decided I didn't need to.

John

[GreenLake]

@K.C. nicely put. There's definitely a love-hate relationship that sailors have towards their auxiliaries.

One final thought: even with a (sufficiently) powerful outboard at hand, it's best to remember that it's supposed to be an auxiliary, and plan your trips so that you primarily rely on sail. Otherwise, you'll quickly want a second outboard as redundancy