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ContinuousWave: Whaler Performance
1974 Outrage 19 -- Kicker Motor Questions
|Author||Topic: 1974 Outrage 19 -- Kicker Motor Questions|
posted 09-24-2004 04:43 AM ET (US)
Does anyone know the displacement hull speed of a classic 19 Outrage? I'm guessing it's 6-7 mph but I'm hoping it's higher. I'd like to add a kicker motor to my 1974 Outrage 19 and I'm wondering what horse power the kicker should be to move my boat at 8 knots in an emergency (assuming 8 knots is even possible). I don't fish so I'm not interested in trolling speeds. I take my boat several miles offshore and would like a "get me home" motor in case the 175HP Johnson fails. I live in the Puget Sound area and would like to be able to power through the 5-7 knot currents commonly found in narrow passageways. Thus, I'd like the kicker to be able to move my boat at least 8 knots. My main outboard is a two-stroke, so I want to stay with a two stroke kicker to share the belly tank when possible. (I'll carry spare fuel for the kicker anyway.)
Also, because my transom has a cut-out all along the back, I can easily mount the kicker directly to the transom without the need of an additional bracket. The port side is easier because the kicker won't interfere with steering and shifter cables. If I mount directly to the transom, a short shaft (15") appears to be a very good size for the kicker, as the cavitation plate will be at the same level as the bottom of the port side of the hull. If I use the short shaft, will I have cavitation problems in rough seas if the stern is lifted in swells?
Does anyone have experience with this hull and kicker motors? What speeds do you get with your kicker? What shaft length works best? I'm looking at 8HP, 9.9HP, and 15HP two-stroke kickers. What speed differences can I expect with these motors? If the speeds are nearly identical, will the larger motors last longer by straining less? Will a larger motor weigh too much?
Thanks for your help.
posted 09-24-2004 09:28 AM ET (US)
Hull speed = 1.34 x square root of waterline length. Assuming you've got 17.5 ft of water line you'd have a hull speed of about 5.6 knotts. Fro my experience that 8hp is the perfect kicker for that hull.
posted 09-24-2004 09:30 PM ET (US)
I have a 1975 19' Outrage with a 6HP 20" shaft 2 stroke Merc kicker. It is perfect for my needs but only pushes it 7 knots max. If you are fighting 5-7 KNOT currents then I would go with at least an 8 HP. Weight shouldn't be an issue so you could go up to a 15 HP especially if is a 2 stroke.
If I were to buy another kicker I would buy a high thrust one with an alternator.
posted 09-26-2004 11:03 PM ET (US)
Boy, 7 knotts with 6 hp, that sounds pretty incredible. That's marlin trolling speed. I don't think even 25 horse will get you 7 knotts or everybody would be using them to troll marlin jigs and saving a fortune on gas. Anyone care to chime in with their top end speeds with their kickers.
posted 09-29-2004 02:43 AM ET (US)
I'm surprised you can get 7 knots with a 6HP also. Is this going downhill ;-)?
Doesn't your 20" shaft place the cavitation plate lower than the bottom of the hull? I'm not talking about the deepest part of the hull under the keel, but the portion of the hull directly under the kicker.
Are the high thrust motors 2-stroke or 4? How do they deliver more thrust yet be rated for the same HP?
Thank you both for your responses.
posted 09-29-2004 10:59 PM ET (US)
"Are the high thrust motors 2-stroke or 4? How do they deliver more thrust yet be rated for the same HP?"
I'm only familiar (slightly) with 4-stroke high thrust. I see no reason why there could not be a 2-stroke one, except for the usual use, which would tend to carbon up 2-strokes.
Oldest high thrust engine I know of would be the British "Seagull". Put one of those on your boat you would go to a fairly good displacement speed (probably slower than you want). Put the same engine on a 30' cruising sailboat and it would do about the same speed. Huge multiblade props on that one, one speed. A outboard stripped of all frills. I used to use one.
Current high thrust motors are equipped with a lower gear ratio, but normally a identical, or near identical power head. Same power head turning the prop slower can turn a bigger prop. It's the bigger prop that's primarily responsible. High thrust simply moves larger volumes of water. The more weight of water it moves the higher the thrust.
Thrust is not just a function of hp, but how it's applied. Thrust is probably more important for moving a boat. This is better known for heavy displacement boats, so that's where the high thrust engines got started. A typical outboard with it's setup for high speed does a really poor job of pushing a large displacement load efficiently. For instance, a Yamaha 9.9 high thrust like I'm getting puts out the same thrust as a standard 15 does, when used to push a displacement load. But, it does it with the gas consumption of a 9.9, not a 15. Displacement requires little horsepower relatively, but lots of thrust if the load is heavy.
The really big advantages of high thrust are generally not at top end speed. There velocity of the water pushed by the motor becomes critical and everything is compromised for that. To get the highest speeds, a great many compromises have been made in engine and prop design. High thrust has it's biggest advantages at medium and slow speeds. If you don't normally do the highest speeds, high thrust, or even just different props may give you a better average performance over the full range of speeds.
On finding your displacement speed, just get out there and try it. Watch the wake, when the bow wave is right at the stern you are pretty close. That will be just before the stern drops and the wake becomes large. Yep, you can calculate numbers, but test will be more accurate for your boat. As soon as the stern drops into the hole, your power needs multiply trying to climb out. You don't have to have a small engine, just throttle that huge engine way down. It'll run you at hull speed. Any reasonable size kicker will not get you out of that hole, find a comfortable speed lower than the hole.
I'm just guessing, but I'd look at high thrust 9.9 at least. Not sure if that will get you 7 mph, but it might. There's a nice article on the site about using a Yamaha T8 kicker on a 22'
BTW, I'm familiar with Puget Sound's currents, though I don't live there. My father's boat "Attitudes" is a 36' motorsailer based in Brownsville that's been all over up there, including offshore, he built it right. The way you do it displacement is to time your travel. Work with the current, don't fight it. You will be amazed how little it's a problem with planning. If you are reduced to your kicker, on a boat not designed for long distance displacement, you will not make it home when planned. Enjoy the trip, don't fight it. Often you will make as good time anchoring and waiting for the turn of the tide as fighting it, and use less fuel.
posted 09-30-2004 02:30 PM ET (US)
The 6HP Merc 2 stroke is the same engine up through 15HP. When I said 7 knots max. that was downhill, with an empty tank, one person, with a 20 Knot wind at my back, and the bimini up. :-) Most likely you would cruise at 4-5 knots. This hull is the easiest planing hull I have ever owned. Look at the minimum HP as per BW. The reserve capacity is 4000 lbs. (2 tons) for a 19 FT boat.
The cavitation plate is below the hull. At trolling speeds it doesn't seem to make a difference and the prop always stays in the water under all conditions. I was concerned that a short shaft would be too short.
I didn't try one though. I would like to know if someone has used a short shaft. For resale reasons a 20" shaft makes more sense if you were to sell the engine seperately.
posted 10-02-2004 02:36 AM ET (US)
Thanks for your input. I'm taking my boat out tomorrow and will check the hull speed as you've described.
If I had the luxury of time I'd plan my trips to match the ebb and flow of the tides. However, most of my boating is done with my family (wife and 3 small kids), so our time on the water is dictated by when we actually manage to make it to the boat ramp. This rarely coincides with the optimal tidal flow!
posted 10-02-2004 10:45 PM ET (US)
I know about time. But you were talking about when one of those trips goes wrong and your main engine says no. Getting back with a small engine will be really helped knowing how to work the currents. Whatever timetable you thought you had went bye bye.
You don't have it like my dad. When his engine blew a seal on the fuel pump and started leaking oil he just shut it down and sailed back. Over the many years he's lost two engines, both times out in the Straits. Once in a storm. Now let's see, where do I step the mast on the Montauk ;-)
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