Choice of kicker size for a 22' Cruiser?

Matt Gurnsey":3eenk9ru said:
The C-Dory hull shape is definately a variable in the equation, as it is a more easily driven hull. Actual performance numbers would be enlightening, especially at full throttle.

I've talked to a lot of kicker buyers who figure if 9.9 is good, 15 must be better, which isn't always the case. I'd probably make more money if I sold them the 15, but in most cases, they don't need it.
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I think you are right on that Matt. When I test my 9.9 HP kicker next year, I plan to precisely calculate the length of the hull at the waterline, and perform WOT testing in calm waters with no current to see if she can go faster then hull speed. What I expect to see for sure is the law of diminishing returns applied. For all I know, which is not much, that extra 2.9 HP above what we need to achieve hull speed at 3,500 pounds total weight may only give us less than a one percent increase in velocity over hull speed!

Even though I would not need 15 HP, if I was buying a new engine, I still would consider that lightweight, fuel-injected kicker to avoid all the Ethanol problems we have on the East Coast. Out in the PNW, you people are lucky! Marinas such as Cap Sante have Ethanol-free fuel. There are no alternatives to Ethanol in the Northeast. What worries me, too, is how long the fuel has been sitting in the tanks -- particularly when we gas up early in the season.

Thanks!

Rich
 
Matt, do you know if that Suzuki 15 comes with electric tilt/trim. From their website it seems it doesn't, unless I missed it. I'm with you on the E10 and EFI.

Thanks
 
At this time the Suzuki does not have power tilt available.

I expect that to be an option in the future, especially when the very similar 9.9 High Thrust does have it. However, there were many small upgrades from the older 15 and the new 15, even though they look very similar. One item we discovered is that the prop shaft is different, so the old props don't fit on the new model.

It may be these small improvements that won't allow the old power tilt to be used on the new motor. I do know that Suzuki has been getting feedback from dealers that we want power tilt, and remote control models as well.
 
Buy a 9.9. They just work well as a kicker. Trolls very well and ridiculously fuel efficient. They are strong enough to point your boat in the right direction in high wind weather. They usually come with a shallow pitched prop with plenty of torque to move a big boat. They can troll from .5 mph to 6.8 mph depending how hard you make it work. 7mph with a strong tail wind is possible.

Chris
 
I just recently purchased a 2013 Tohatsu 6hp 4-stroke kicker for my 2007 CD 22. I'm really liking it, as I have taken it out the last few days breaking it in. I have found that at 3/4 throttle, or at about 4000 RPM I'm getting about 4.5 mph on the GPS. Run it up to full throttle, which right now is only giving me about 4400 rpm, and I can just get to 5mph. Several things here. I have decided to forego any kind of steering linkage to the main. The tiller on the kicker works just fine, and I'm also finding in calmer water, I can tighten the "turn" knob on the kicker to lock it into a straight position, then lower the main and use it as a rudder. I might see about .4mph reduction in drag, if that much. Also, if I tilt the main up, I'm not sure a linkage between the two would work anyway. Ok, as I said earlier, my WOT is about 4400 rpm. This motor is suppose to run 5000-6000 rpm at WOT. The prop that came with it is a 7.8x8 (8 being the pitch.) I'm thinking I need to go with a smaller pitch to get the rpm's up so the motor is not working so hard. Have others experienced this problem with putting the Tohatsu 6 on the CD-22, and if so, have you changed props and gotten it up to specs? Colby
 
We have the Nissan 8hp 4 stroke with electric start, and I believe it's 86 pounds. It will push the boat 7 mph WOT and it trolls excellent. The tie rod to connect to the main is well worth it, IMHO. Yes, you can tilt up and still use it, at least on ours.

Rick
 
Rick, do you have any photos of your linkage set up. I did just go look at your boats photo album here but didn't see any. Colby
 
Because I wanted a dual-purpose kicker to put on the dink and for trolling, I picked the Tohatsu 6hp extra long shaft. It pushes the Dory just under 5knots full throttle and is just barely useable on the 7' inflatable. If I were to do it over again, I would get a 8 or 9.9 fixed trolling/aux engine and get a 2-3hp for the dink.
 
hmm.. I'll have to check and see if I could mount in that location. I've got the Merc 115 4 stroke, with power steering. Not sure I have the same kind of mounting area. The other linkages I had seen mounted on the ventilation plates, and that would not work with the main tilted up. Thanks for the photo. Colby
 
The new 15/20HP injected Suzuki run from 97lbs to 108 lbs (long shaft electric start). I would think long and hard about getting a smaller motor if I were ever to want to move the motor over to a 15'-16' aluminium skiff. We rent a 16' with 15HP two stroke every year when we go to Lake Shasta to house boat. Load the boat up and 15HP is just enough. At WOT it eats gas! We can burn 3-5 gallons a day in a heart beat as it is much cheaper to run the skiff flat out and leave the houseboat moored to the beach. Last trip we used under 8 gallons of gas for a full week on the houseboat/generator (four cylinder monster) but we put 3+ gallons in the skiff everyday. For me, I would get the 20HP with electric start, we like that on the skiff we rent and it is easier for the wife.
bob
 
The prop for a "Kicker" is going to be entirely different than what you will have as a stock prop on most of these smaller (6 to 15 hp) engines. It will be max diameter (some of the high thrust outboards allow a prop of greater diameter). The pitch will be considerably lower, and allow you to reach 5500 RPM at WOT. There will be larger blades, often with little cup if any.

A true displacement boat (think round bottom, with no appreciable chines) will be limited at somewhere close to the 1.34 x sq root LWL. You can apply more HP and it will not go much faster than this, as it digs a bigger hole in the water.

A planing hull, as the C Dory will go faster than the theoretical "hull speed". The more hp, along with an appropriate prop will go faster, but there will be a limit. We know it takes about 50 hp to get a light C Dory 22 up on a plane--maybe 12 knots or so (I know that some claim planing at less, but you are actually using more HP, at the lower planing speed.
 
Bob, I'm assuming your comments were for me. But if not, they still kind of address my question, but not quite entirely. ;-) Let me rephrase it. For those of you with kickers in the 5-6 HP range, what size prop are you using? Mine came with a 7.8 x 8, but I'm only getting 4400 rpms at WOT, and I need to be in the range of 5000-6000. Thanks. Colby
 
Colbysmith, yes, the post was in general, but specifically toward your problem There are two 6 hp--one is the sail drive, which has a slightly lower gear ration in the lower unit, and can swing a slightly larger prop--and would be best. However, I assume that you have the standard 6 hp, which comes with the 8" pitch prop.

First a question--what tach are you using?

You would expect for each inch decrease in pitch that you would gain 200 RPM--however, the 6" prop (smallest pitch I could find for this engine), is 0.2 inches more diameter--which may decrease the RPM slightly (maybe 80 RPM).

Here is a quote from Sailnet by audeojude. Where a tach was put on a 6 hp standard Tohatsu and the 8" and 6" props were compared with a strain gauge:

"engines with the 8 pitch prop could only turn 3700 to 3800 rpm and produce an average 124 lbs of thrust. With the 6 pitch prop they both turn about 4300 rpm and produce an average of 165 lbs of thrust. .

This is with a static load; you may get slightly more RPM with the boat moving, since it may allow more RPM (see your 4400 PRM vs their 3700 to 3800 static). Thus there is a good chance that with the boat moving, that a gain of 500 RPM will bring you very close to the 5000 RPM. Having said that, I would not run the engine at max RPM, I would go down to where it is moving the boat easily, and that may be about 4000 to 4200 RPM.
 
Colby
There is away to tie your Merc with hydralic steering using that tie bar set up. I did it with my 90 Merc unfourtunatly I dont have pictures. But I used a piece of aluminum barstock 1/4 x 1x8 inches that I screwed to the front of the motor right above the hydralic cylinder. If I remember right there is a handle like part on the motor that already had two holes drilled for cable linkage I think. Just screw up from below and counter sink your screws so that they dont interfere with your hydralics cylinder. Offset the bar so that you have a couple inches sticking out on you kicker side. Drill a hole for the ball connector of the tie bar And you are good to go. The down side of this for me was the geometry of the set up. I had to make compromises on turn radiuses. I could adjust to make full left turns or full right turns but not both. This was caused by the way the setup is mounted on the main with hydralic steering. You will see if you go this route. anyway again sorry that there are no pictures and I hope that I made some kind of sense to you as far as the set up goes.
 
Bob,
The Tach I'm using is a nice little one I just recently purchased. Hardline HR-8061-2.
http://www.amazon.com/gp/product/B000FO ... UTF8&psc=1
Seems to be pretty accurate. At least if the Kicker is idling where the factory says it's suppose to be. (Around 1300, which is what the little hour/tachometer reads when it's at idle.) (I ended up running the wire thru the grommet where the front shifter rod comes out, and then tie stripped the gauge to the bar across the front of the motor.) As I break the motor in, I'm getting about 4 mph at 3/4 throttle, which is probably where I would run it (or slower) while trolling. (Also, I don't really seem to gain much more speed by running WOT.) My WOT RPM concern is that if the engine isn't able to produce the spec'd 5000-6000, then perhaps it's working too hard with the prop that's on it. I did go ahead and order a 7.8 x 7 (one size down) Solas Prop from iboats. I'm hoping that prop works a little better. BTW, yes I've got the standard 6hp, with 20" shaft. (or is it 25?) Anyway, it's not the short shaft, but the next standard size. I did look at my engine earlier today, and don't think I could get much larger diameter prop on it, as there is not a lot of clearance with the ventilation plate. Colby
 
Chuck,
I'll have to look at the one earlier photo a little closer and see if there is a way to rig it on my boat. My Kicker sits back on the minijacker, which is also spaced about another inch aft. So I would probably need to fabricate something on the kicker to bring a ball mount forward 5 or 6 inches. The Merc 115 does have the two holes in that bar on the front of it. While I have been ok with steering with the tiller, or using the main as a rudder, if I could get an inexpensive linkage to work out, that would be better. Ok, I've reread your comments a few times, and I think I understand what you are saying. I understand that the barstock you attached is in line with that bar on the front of the engine, and basically extends it towards the Kicker. Then you set your linkage off of that bar, to the kicker. That might work with my set up. I'll need to think about it all a little more. Colby
 
Colby
You got the idea. If I remember correct the bar on the front of your Merc already has counter sunk holes . Just come up from below with your screws It may not be the prettiest setup, and like I said it does have its limits, but it does work
 
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