How fast will a kicker motor push a 21 footer?

[mbb]

Re: How fast will a kicker motor push a 21 footer?

I got a yamaha 9.9 4S high thrust. It puts out incredible thrust, similar to what you could get with a 25-30 hp. It doesnt have a prop, it has a FAN. Big dia/low pitch. But about 5-7 mph is all I get, at 2/3 throttle, no more at full.

 

[letsbarbq]

Re: How fast will a kicker motor push a 21 footer?

thats sounds better than not moving at all in the middle of no whre.... how big is your boat..????

 

[BobZ]

Re: How fast will a kicker motor push a 21 footer?

There are a lot of kicker motors used on the Great Lakes here in the midwest. Folks are likeing the 4 strokes because they are quiet and there are no fumes.<br /><br />Boats with wide transom cutouts sometimes have enough room to mount the kicker next to the big outboard. If you mount it on the transom cutout you will tilt the kicker motor up when you plane with the big engine. A number of fisherman have lost the kicker motor overboard because the motor mounting bracket breaks from the pounding from rough water while in the up position. So beware and check for special motor mounting brackets for transom mounting.<br /><br />If you don't have the transom cutout room or have an I/O, like I have, you then need a lift bracket mount that bolts to the transom. The lift bracket allows for the kicker to move up and down so you can get it out of the water when you want to plane with the big engine. (Most cases you do not need to tilt the kicker) My lift is elec/mech and has a 14" travel lift.<br /><br />One problem to be aware of with a lift bracket. Most will have a max. capacity of 100 lbs for the kicker. Not a problem for a 10 or 15 HP 2 stroke - but a 10 HP 4 stroke usually weighs around a 100 + lbs.<br /><br />Most of the kickers on the Great lakes are 10 or 15 HP. If you lose the big motor your not going to plane the boat anyway so you don't need anymore horsepower than that. They will move a 5 - 6,000 boat at 6 to 7 MPH max. Twenty horse power won't move it any faster because you now have a displacement hull rather that a planing hull. <br /><br />Another thought. If you get a kicker on a bracket you will want at least a 20" lower unit.

 

[letsbarbq]

Re: How fast will a kicker motor push a 21 footer?

Hello Bob from Detroit,<br /><br />your entry hit the bullseye. That was the information i needed. yes, i thought about oing with a 20-25 hp motor. but if you say that a 15hp will make the boat go the same speed as a 20-25hp, then i dont need the bigger engine.

 

[JB]

Re: How fast will a kicker motor push a 21 footer?

Ahoy, Len. Just to amplify Bob's very good post: Every boat has a "displacement" speed. To get above that you must approach "planing" speed. Once a boat reaches it's displacement speed it usually requires double or triple the horsepower to get it "up" to planing speed.<br /><br />The perfect kicker will reach the displacement speed of your boat, with no extra hp , cost, or fuel usage. On your boat that should be 10 to 15HP.<br /><br />Red sky at night. . .<br />JB