Honda 15

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chicagocat
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Re: Honda 15

Post by chicagocat »

Hi Terry,

The Torqeedo 4.0 R would likely work. It's rated at about 9 hp, and the shaft is about 20". It's a bit expensive, at about 3K. But it would be nice and quiet.

Regarding shaft length: I know that the Yamaha 9.9 everyone uses is the 25" shaft. But looking at mine, I think a 20" shaft would work. The cavitation plate on my 9.9 is at least 6" below the water currently. But most sources say that the cavitation plate should be right about at the water line. So I think that the 20" shaft would be fine.
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and 2001 PDQ 36 Classic (Tall Rig)- "Cat Tales" - Punta Gorda, FL
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Re: Honda 15

Post by doubledutch »

Having experienced white knuckle docking with the 9.9 Yammies on full throttle trying to maintain control in high winds I would not consider the Torquedo. They develop only 280 lb. of thrust vs 250 for the 9.9 s. I have looked at the Ray Electric outboards which claim 250 lb. thrust in their 60 volt version - they might be up to the task.
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Re: Honda 15

Post by ATTITUDE »

Greetings to All:

When I added Honda 15's to ATTITUDE, I initially had them mounted to high. This resulted in ventilation* (often confused with cavitation) whenever I was waked. The solution was to mount the motors closer to the water. Since then, no problem.

This past summer ATTITUDE journeyed from Stuart, FL to Bermuda and returned via the Abacos. WHAT A TRIP!!!!!!!!!!!!!!! ATTITUDE, a 2000 Capella, and the Honda's performed perfectly!

Doug

* Ventilation is a phenomenon that occurs when surface air or exhaust gas (in the case of motors equipped with through-hub exhaust) is drawn into the spinning propeller blades. With the propeller pushing mostly air instead of water, the load on the engine is greatly reduced, causing the engine to race and the prop to spin fast enough to result in cavitation, at which point little thrust is generated at all. The condition continues until the prop slows enough for the air bubbles to rise to the surface.[4] The primary causes of ventilation are: motor mounted too high, motor trimmed out excessively, damage to the antiventilation plate, damage to propeller, foreign object lodged in the diffuser ring.
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Re: Honda 15

Post by mikeandrebecca »

ATTITUDE wrote:* Ventilation is a phenomenon that occurs when surface air or exhaust gas (in the case of motors equipped with through-hub exhaust) is drawn into the spinning propeller blades. With the propeller pushing mostly air instead of water, the load on the engine is greatly reduced, causing the engine to race and the prop to spin fast enough to result in cavitation, at which point little thrust is generated at all. The condition continues until the prop slows enough for the air bubbles to rise to the surface.[4] The primary causes of ventilation are: motor mounted too high, motor trimmed out excessively, damage to the antiventilation plate, damage to propeller, foreign object lodged in the diffuser ring.
I don't want to hijack this thread, because I am quite interested in the discussion, but this sounds like what was happening intermittently yesterday to the 9.9 Yamaha 2 stroke mounted on our dinghy.
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Re: Honda 15

Post by chicagocat »

HI Doug,

What shaft length are your Honda 15s?

Thanks
PDQ 36052 - 1996 LRC - "Anne Z" - Chicago
and 2001 PDQ 36 Classic (Tall Rig)- "Cat Tales" - Punta Gorda, FL
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Re: Honda 15

Post by Page 83 »

I've looked at the Torqedo's pretty hard. It's perfectly do-able, provides some interesting advantages, but will cost* as much as five Yamaha 9.9 High Thrust engines, filters, oil and parts for 2000 hours, allowing for inflation. And that does not include a generator which would be necessary if you were cruising away from nightly shore-power. The most intriguing bonus is the ability to steer the motors far enough left or right to power the vessel sideways, into or out of a windward T head.

*The price of two Torqedo HP motors (48 volts required), 8 lithium batteries, proper sized cables and charger plus modifications to the nacelles. If you want to replace the amps you burned during the day by running a generator at the same time or longer, the price doubles again. A wind generator and a big array of solar panels might work in the islands where there are an abundance of breeze and sunshine might accomplish part of that load. But they won't get you down the ditch.
Sandy Daugherty "Page 83" PDQ 36026
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Re: Honda 15

Post by Page 83 »

I have commented here before about alternate engines for PDQs, Seawinds, Geminis and Maine Cats. I will again. Here are some facts to consider:
Four stroke engines have a power curve (very similar among all the engines in this category) that peaks at the designated maximum operating RPM, and manufacturers install speed limiters to achieve the longevity expected of their product.
The driveshaft turns at engine rpm, which is reduced at the lower end, with a specified gear ratio, as found in published specs.
A propeller is designed to consume a specified amount of power at a specific speed through the water, and a particular rpm.
Small diameter propellers must turn faster to deliver the same amount of thrust as a larger diameter propeller turning at a slower RPM, but they sacrifice a lot of efficiency in doing so. The most efficient propeller blade is long and narrow. The most efficient propeller has, believe it or not, one blade.
With the exception of the Yamaha High Thrust Series (and not all of them!) outboards between 5 and thirty five horsepower are built for small open planing boats that might expect to run between 15 and 25 knots. The engines have gear ratios and propellers designed to reach their maximum horsepower at those speeds.
At slower speeds, these engines are not turning at best power. At the range of speeds that our catamarans are capable of (without assistance from sails) these engines are running as much as a thousand rpm lower than max power, or they are cavitating. This is apparent in the amount of white water in the prop wash. They are putting as little as half their advertised horsepower into the water. And they are burning gas at the full throttle rate.
Our cats cruise under power at eight knots or less. They go faster under sail, which can develop as much as sixty horsepower on a beam reach in twenty five knots of breeze. In smooth water that makes for a very exciting ride.
Meanwhile, back under the engine hatches, we find only two available engines that put out almost their rated power at 8 knots. Those are the Yamaha 8 and 9.9 HP high thrust engines; they have almost a 3:1 gear ratio, and the lower unit has enough room for an eleven inch plus diameter propeller. My eights turn 5400 rpm at full throttle producing 7 knots on my very heavy PDQ 36 with a clean bottom and bare poles in no wind. This is the actual average of four timed laps up and down wind in calm water.
Time for a little independent research. Collect the numbers for all the engines you are interested in, and study them. You will find that Hondas and Tohatsu's and Mercury's and Suzukis may have decals that say "big Foot" or "High output" but they have gear ratio's much closer to 2:1, and lower units that can't accommodate larger diameter propellers. Don't believe me, go look for yourself. What this means is that you can't put a prop on them that will maximize their performance at eight knots. If there's enough horse power, opening the throttle will spin the prop and cavitate.
For the record, I think Yamaha Outboard as a company sucks. I drive a Honda Van, I've owned several Honda Motorcycles, and if Honda made Wheaties I'd have them for breakfast. I would love to put a Honda outboard on my PDQ, but it would not work as well and the Yamahas. Would a new Honda 15 or 20 move the boat faster than some clapped out Yammies? Probably. Would it move the boat faster than a pair of newish, well maintained 9.9's? I think you know the answer now. But even I would rather give my money to Honda than Yamaha. Except....
Those are the facts. Here is the anecdotal evidence.
I owned a Simpson Wildcat before Page 83. It was powered by a Honda BF50. Thats right, FIFTY horsepower. I could open the throttle wide and the engine would scream but we wouldn't go anywhere. The engine was more than deep enough, but it was obviously cavitating, not ventilating. A solid column of white shot out under water for a distance of 20 or 30 feet, and a wispy cloud of steam bubbled up, but there was no whirlpool above the lower end indicating it was sucking air. If I gradually opened the throttle and let the boat accelerate to full speed, I could jam the throttle forward with no apparent effect other than a change in the sound (and fuel consumption). It was clearly over propped for the 8 knots it reached.
Sandy Daugherty "Page 83" PDQ 36026
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Ed Ellis
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Re: Honda 15

Post by Ed Ellis »

I had Honda 15s - no they don't clear the water plus, mine got eaten up by electrolisys. Also, there are lots of parts on the Hondas that rust... Rather badly. I went back to Yamahas and won't consider using Hondas again.
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Re: Honda 15

Post by Page 83 »

Our PDQs are displacement hulls. They do not plane. The speed advantage comes from having narrow beams, and works fine to a point, but we still hit the wall, requiring more and more power to go less and less faster.

If we can occasionally sail at 12 knots sustained, why can't we motor at the same speed? It's a bit complicated, with several considerations such as: Thrust from the sails comes from above the waterline, preventing the bows from rising a bit. Thrust from the engines comes from under the waterline, allowing the bows to rise a bit, shortening the waterline. The result is another component in the equation that increasing power yields diminishing results.

I am sure that if there were a good place to mount them, a couple of 100 hp outboards would yield some double digit speeds, but the ultimate limiting factor, common sense, rules out that option.... :wink:

There was a cat for sale when I was working at Chesapeake Catamaran Center that had some really big outdrives, the theory being that you could pull a skier if you wanted to. Maybe a twelve-year-old skier. At something like twenty MPH. It didn't sail well.

So we're stuck; our boats work best within some practical limitations. We can motor at 7 or possibly 8 knots with reasonable fuel consumption. We can sail faster with the engines out of the water, and with less weight on board. We can maneuver with control up to a certain set of wind and wave conditions, beyond which drastic measures are required, like dropping an anchor or a drogue. Cautious seamanship may reduce our exposure to these conditions, but we must be prepared to meet them before they imperil vessel and occupants, weasels included. [does West Marine carry ferret preservers?]

I have heard that a certain un-named PDQ 36 was taken under tow after an unfortunate miscalculation of fuel capacity, but that Mr. Towboat had to run his twin 150's at full throttle to get both boats up to 10 knots. Purely an apocryphal report of course. Completely unscientific too; wind and wave conditions were not recorded. And no, it wasn't me (this time.)

So the bottom lines is this. The powerhead of the outboard is virtually irrelevant. What makes or breaks motoring in a sub 38' cat is the lower end, how deep it is, what the gear ratio is, and how big a prop it can spin.
Sandy Daugherty "Page 83" PDQ 36026
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Re: Honda 15

Post by thinwater »

Before my PDQ (7.2 knots with 2 x 9.9 Yamahas) I had a Stiletto 27. It came with a 8hp Seahorse (7.5 knots) which I upgraded to 15 hp Nissan (13.2 knots).

I did actually re-prop the Nissan, because in that year the prop was relatively slow. But here is the difference; the Stiletto wieghs 1300 pounds stripped bare and will get up on a semi-plane because of rather flat sections (she also pounds like hell). However, If I added a cruising load, water, fuel, another person and perhaps just a little fouling... 10.5 knots and terrible mileage.

Getting more speed from a PDQ is dreaming. Often I run on one engine just to save noise.
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Re: Honda 15

Post by Tom Green »

Unrelated use but I have a Torquedo on my dinghy. I like it for that application. It is clean, quiet and no other liquid fuel needed. It is also very light and easy to lift from the water and to remove from the dinghy and store.
I have not used it a great deal but the power is consumed fairly quickly if you run at at higher speeds. I would think for long hauls that would be a problem. They also represent that you can keep it running at a moderate speed with
a solar panel connection.
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