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In a different thread I posted on my experience with Aux motors and was coached to post this in a seperate thread as HarleyFXDL would like some data on performance of aux motors from 3-30hp for an article.

My tests this winter...
Test Boat 73 Montauk (non-smirk)
Main motor is a 1994 Mercury 75hp left in down position for all tests.
All tests were done with just me (300lbs) and 20 gals of fuel and my normal fishing gear.
Batteries mounted in Console and gas tank under the RPS.
Speed taken from GPS.
All aux motors mounted direct to transom on Starboard side. (one at a time of course)
Tests done in Saltwater estuary at slack tide with several runs and speed averaging.

55lb Thrust Electric motor max 2.5-MPH at WOT (Group 27 trolling battery on port side rear).
3hp 2-stroke long shaft Johnson 3.5mph at WOT. (built-in gas tank) (approx 30lbs)
5hp 4-stroke short shaft Honda no good too much cavitation 3.5mph. (used existing gas tank)
6hp 4-stroke long shaft Mercury 5.5mph at WOT. (used existing gas tank)
7.5hp 4-stroke long shaft Honda 5.5mph at WOT. (used existing gas tank)

Please feel free to post your experiences.

(edited content below)

The smoothest motor was the Honda 7.5 with twin cylinders. The Mercusy 6 was smoother than the Honda 5, actually the Johnson 3 was smoother than the Honda 5 but the loudest motor was the Johnson 3 at WOT. At half throttle all motors were reasonably quiet and smooth enough for me.

The electric was the quietest motor.
The Honda 7.5 was quieter than the Merc 6 or the Honda 5.
I could be quite satisfied with the Merc 6 or the Honda 7.5

Weights
Electric with battery about 85lbs
3hp about 30lbs
5hp 60lbs
6hp 55-60lbs (mercury only gives weight for short shaft)
7.5hp 76lbs

Weight was not a problem with any of the motors except once in a heavy following chop with two 300 lb guys in the stern and the electric w/battery back there I got a little nervous about the possibility of water coming over the transom. It was pretty close. But to put it in perspective we had close to 1000 lbs at the extreme rear of the boat and no body forward of the RPS.

Regards Tim C.

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Hi Tim,

Great topic! Other data would also be interesting like vibration and sound. I am about to go for a gas powered kicker. My primary criteria is weight and noise. I am sure that a 4 or 5 HP will push 17ft with no problem even in a wind or current.

Thoughts from anyone?? Thanks for bringing this up Tim.

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My nissan 4 stroke 6 hp pushes my Nauest well for trolling, but when the wind comes up in the bay, it needs to be revved up pretty high, perhaps 3/4 throttle. Getting home in case of a main motor failure woud take forever.

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Try to avoid a single cylinder motor as the vibrations will dislodge some fillings. I have a nice little 4hp Yamaha with a single cylinder. I now see why the motor had little use and looks new. This little monster could whip up some pina coladas from the vibrations it puts out. I have a 6hp Evinrude with twin cylinders. Very smooth compared to the 4hp. The 4-stroke Yamaha 9.9 I had on my Montauk pushed the boat fine. I figure, maxed out, it did about 5 mph and was fairly smooth. I feel a 6hp would have done the same job. I would imagine needing a bigger motor, prop'd correctly, for a bigger boat. When I get the time and boat, I would like to try out a few different motors and record the findings on here.

Kevin

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I don't think any kicker motor will go faster than between 6 to 8 MPH top speed no matter what size kicker you have. Unless the boat get on plane, you max out at the approximate hull speed listed above.

Most people don't understand the above as it doesn't seem logical. But that's the way it is. Max hull speed without being on plane...

My 8 hp pushed my prior Montauk and current Outrage 18' about this same speed.

GPS is a good way to measure your speed as long as you average both directions.
Otherwise, a fairly accurate paddlewheel will give you your Speed Over Water which should be fairly close to the average GPS speed taken by going inn opposite directions.

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Joe, didn't you have a 25hp as a kicker on one of your boats?

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Harley,

You have good eyes...
Yes... It came with the 1989 Outrage 22' Cuddy.
Mike (the prior owner) bought the kicker for a great price as it also matched the main motor which was also a 1999 Johnson...
I never tested it out on the water as it was also electric start. Never finished hooking it up before I sold the Cuddy.

[img]http://users.sisqtel.net/jkriz/Outrage22/Outrage22.jpg[/img]

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I would imagine the 25 wouldn't do any better a job than a 8hp. The only advantage I could see would be the 25hp could swing a big diameter prop for more thrust. On my montauk, the 9.9 took some distance to go from 5 mph forward motion to stopping the boat and proceeding in reverse. I would assume the 25 could do that in half the distance.

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BTW Joe, how did you like the 1999 Johnson main motor? The boat I'm looking at has the same year in 150hp.