Hight thrust kicker vs standard kicker
I am looking into getting a kicker for my 22' glasply. I am looking to get one not only for trolling but also for a backup power source incase my main went down on me. What are the advantages of a high thrust kicker. Would a regular outboard get the job done? I am looking at either a 15hp or 9.9hp. Any help, advice, and or opinions would be appreciated.
I think the main difference (there may be others) between a regular small outboard and a high-thrust small outboard is propeller pitch. Regular has a higher pitch. High-thrust has a lower pitch. Each is suitable for a different purpose. A small outboard could be a main source of power on a small planing boat, i.e. a dinghy (this is the regular motor application), or it could be an auxiliary on a larger boat (the high-thrust application). On the small boat, the motor would be capable of operating at higher planing speeds. On your larger boat, the maximum hull speed using the auxiliary would be much slower.
To produce its rated horsepower, a motor has to be able to reach a certain (fairly high) rpm. For the small planing boat, a higher pitch propeller is used so that this rpm is achieved at planing speed. If the same regular motor were mounted on your larger boat, wide open throttle would not be able to produce enough engines speed to reach rated power because the larger, heavier hull won't let the motor move fast enough through the water. The solution for using a small motor on a larger boat is to decrease the propeller pitch so that high rpm is possible at slow hull speeds.
It's a little bit like the gearing on a vehicle. If you could choose only one gear, for slow speed operation you would choose a low gear. For high speed operation (provided you had enough horsepower to operate at high speed), you would choose a higher gear.
Yes like rifleman said the pitch is different and a lot of the high thrust also use a 4 blade prop instead of the standard 3 blade. They are able to push the more aggressive pitch because the gearing is lower than a standard kicker.
My yamaha high thrust 8hp is lower geared allowing it to use a larger dia. prop. It is a lower pitch but it moves more water allowing better controll at lower rpm's. Not all makes use the same design. Mercury and yamaha do it this way, but I think honda uses just a 4-bladed prop. It works great on my 22' Hewes, very good control in tight spaces ,like the dock.. The dia. of the prop on my 8hp is almost as large as the prop on the 115hp yama I had on there.
For a dedicated kicker, the high thrust is the way to go. For displacement speeds, it is more efficient for the engine to be geared lower and swing a larger dia prop, which is exactly what you are doing with a kicker. For a dinghy or small skiff where you want to get up on plane, a traditionally geared and propped small outboard is the best setup.
High thrust is really a misnomer, a more accurate description would be properly geared and propped for the task.
My 31' boat weighs 12,000lbs, and I have a 9.9HT Yamaha kicker. It pushes the boat at 5kts in calm conditions. I am still on the fence if this is enough motor or not, since I have not tested it yet in big waves or much wind. I read somewhere that the High Thrust 9.9's are equlvalent to a 25 or 30HP regular motor, but I cannot recall where I saw this at.
It is definately fine as a kicker for trolling. I kow others that have the 8PH HT motor on the same size boat as mine and they say it is fine.
I am not impressed with the cold starting of the Yamaha. I also have a 9.9 Honda and it is much smoother starting when cold than the Yamaha is.
Originally Posted by jrogers
My boat weighs half as much as yours so I am convinced that if your 9.9 can push your boat at 5 knots, then it would be OK for my boat as a back up. I have been looking at the different manufactuers 15 hp and it doesn't look like they make that hp with the same gearing as the 9.9 or 8, too bad because I would like the extra 5 horsepower.
High Thrust kicker
I have a Honda 9.9 with 4 bladed high thrust prop and I see about 6-7 mph with the lower unit down for steering. With the lower unit up I see about 9 mph but I have to steer the boat with the Honda, not an easy thing to do.
Along the way I found out that the Honda 9.9 hp and the 15 hp are basically the same engine. Before they went all electronic you could turn a 9.9 into a 15 by changing the throttle stop on the on the carburator. I also run the Honda kicker off the main tank so in theroy I might be able to make Hawaii from Seward on 150 gallons (just kidding).