Kicker Motor Performance/Speed

[bkuhn]

I have a 2000 X and am looking to add a small kicker motor to it. I'm trying to determine what the minimum reasonable HP needed is. Ideally I'd like to be doing 5 - 6 knots and trying to determine how many HP I'd need to do that. My goal is to have a backup to the primary motor, but also to have a more fuel efficient and quieter option for longer motoring (the primary motor is a 2 cycle 50hp Nissan).

The challenge is that the boat shop I am talking with says that mounting a 6hp might be all we can do because of the limited mounting space (thus limited options for a motor mount). A larger bracket would be required for a 9.9hp (heavier engine) and they don't think that it's possible.

So my question is, does anyone have an auxiliary motor somewhere ranging between 5 and 9.9hp on an X or M, and if so can you tell me what sort of speed you get out of that motor?

Appreciate any feedback from anyone with experience in this area. Thank you!

[rsvpasap]

Suzuki DF6

[kurz]

Interesting. How about gas consumption? Same speed and both motors? Which one wins the challenge?

[rsvpasap]

Suzuki DF6

[Russ]

I have a Suzuki 2.5 on my inflatable dinghy. On flat conditions, it can push the mac pretty fast. Amazing it can do that.

[NiceAft]

I have a Suzuki 2.5 on my inflatable dinghy. On flat conditions, it can push the mac pretty fast. Amazing it can do that.

Russ,

How is your Suzuki fastened to your M? I know Highlander created a specially shaped mount for his kicker. The M is far more difficult to attach a kicker to the stern than an X.

[Russ]

I have a Suzuki 2.5 on my inflatable dinghy. On flat conditions, it can push the mac pretty fast. Amazing it can do that.

Russ,

How is your Suzuki fastened to your M? I know Highlander created a specially shaped mount for his kicker. The M is far more difficult to attach a kicker to the stern than an X.

Oh, it's not attached to the Mac. My son was in the dinghy "pushing" the Mac with the motor on the dinghy. I can't remember but it seemed like we got 4-5 MPH out of it. I was amazed.

My comment was intended to show how little HP will move these boats.

[NiceAft]

I understand what you were communicating; I just wasn’t sure whether you had a kicker on your blue Mac, or were pushing it.

I have a 6hp, 4 stroke Merc on my Achilles. Now I’m going to try and convince the admiral to take command of the dingy, and try it with our M.

[Be Free]

Interesting. How about gas consumption? Same speed and both motors? Which one wins the challenge?

Kurtz,
I have a Honda BF40D on a heavily loaded 26X. At 3.5 knots I get 10 NMPG. At that speed ballast in or out did not make a noticeable difference after the boat was moving.

Bill

[wakataka]

I've got a 5hp Tohatsu 2-stroke kicker. At full throttle it will push the boat fully loaded with the boards down at 4.9 knots turning 4700 rpm. It's turning a 7" pitch prop, which is as flat as I could find for this motor but it still won't quite make 5000 rpm pushing this heavy a boat. A more comfortable 3/4 throttle cruising speed is about 4.3 knots.

The manual says it should burn about 0.7 gph at 5000 rpm. This is the same fuel burn as I would see at 4.9 knots using my main motor (a carburetted Yamaha F-50), so the two-stroke kicker won't save me any fuel. I suspect a 4 stroke kicker would be substantially more efficient than your 50hp 2-stroke, however.

One thing you need to consider. With the kicker being mounted off to one side the prop can come out of the water when the boat rolls. The kicker is best used in fairly flat conditions.

[NiceAft]

One thing you need to consider. With the kicker being mounted off to one side the prop can come out of the water when the boat rolls. The kicker is best used in fairly flat conditions.

Good point I never thought about that

[kurz]

One thing you need to consider. With the kicker being mounted off to one side the prop can come out of the water when the boat rolls. The kicker is best used in fairly flat conditions.

Do you normaly use short or long shaft for the kickers?

[wakataka]

Do you normaly use short or long shaft for the kickers?

I've used both. I think long shaft works better, particularly if you can find a 'long-throw' mount. Most standard trolling motor mounts don't have enough travel to keep the motor clear of the water when sailing and still put it far enough down in the water when in use. The standard kicker mounts are made for motor boats that don't heel over when sailing or roll as much as sailboats do.

If you can tilt the motor up when not in use the prop will stay mostly clear of the water. I tried a 6 hp Nissan on my mount and it was too big to tilt. The motor cowl would hit the transom before the tilt locks engaged. I could probably have shimmed the mount back about an inch and made it work. The 5 hp Tohastu just clears the transom when tilted, and the little 4 hp Johnson I had before that had plenty of room to tilt. If the motor isn't tilted, the prop will constantly drag in the water when sailing on port tack (motor was mounted on starboard side of transom). With the motor tilted, the prop can still drag but only when heeled way over.

[Chinook]

I carry a 2.5 hp 4 stroke Suzuki kicker on a retractable stern mount. It's a short shaft motor, and when the mount is lowered, the prop is deep enough to power the Mac. I mainly use the kicker on my inflatable dinghy. I also use it to power the Mac when I'm trolling for salmon, using a downrigger. I fish at speeds of 2 knots or so. I lock the kicker down so it pushes the boat straight ahead and steer with the rudders. I have used the kicker in emergency situations when the big engine failed, however it has serious limitations. While it can get me up to 4 or 5 knots, that's only on flat water with no headwind. If there's any degree of swell or chop, it definitely slows down, and it has real trouble making any kind of headway at all if I'm trying to buck a strong headwind. I've even had it completely stall out and fail to start when I was trying to counter a dragging anchor in 40 knot winds.
Also, it has trouble making turns if the wind is strong. I usually need to lean back over the stern and manually turn the kicker, which is awkward to say the least, since I can no longer see where I'm going. It's best relied on for going a short distance or getting around in protected waters. In open water, the sails are your best option for backup in the case of engine failure. One additional limitation in relying on the kicker to get you long distances is the fact that it utilizes a built in fuel tank, with very limited capacity, which will get consumed rather quickly if operated at full throttle. That means that you need to lean over the stern and refill the tank while bobbing out in open waters, which likely results in a fair amount of fuel spillage.

[bkuhn]

I wanted to post a reply in hopes that it might help someone in the future.

I ended up going with a 6hp 4cycle long shaft. The shop was able to mount a larger adjustable transom on the X capable of handling a 9.9hp. But they also had a used 6hp avaialble (only 2 hours on it, still under warranty) and agreed to let me take it out to test and see if it was sufficient.

Turns out it was. Very much so. What I found was that at about half throttle it pushes my X at just under 6 knots (with the water balast full). At full throttle I could get just about 7. So I take that to mean that a 9.9 would probably get me very little additional speed and probably just burn a lot more fuel. My conclusion was that a 6hp was more than adequate and it's also extremely fuel efficient.

Hopefully this helps someone in the future if they are strugglign wtih the same question I had when I posted this originally.