# Why are HP ratings different for a tiller?



## BLKLAB (Jul 27, 2012)

I'm curious why the HP ratings are always lower for a tiller as they are for remote? I've thought about weight or maybe balance? Most boats mount the consoles right where you would sit if you were running a tiller so that doesnt make sense?


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## shawnfish (Jul 27, 2012)

by being different how do you mean? for a certain model boat? i


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## Johny25 (Jul 27, 2012)

The two reasons I know of are weight distribution and torque of the motor. Console type boats usually have the console forward of where you would have to be to operate a tiller style motor. And really I have never seen a console as far back as to where you could run a tiller, although I am sure someone has probably made one like this. With the console and weight being further forward it changes the C of G of the boat for the operator. Take a full throttle turn at the helm of a console boat and then try one at the tiller position, a lot more force and chance to throw yourself out in the tiller seat. 

Then you have the torque of the motor. Good example is a lot of tins are rated 15hp tiller but 25hp console. Overcoming the torque slap of a 15hp motor at say 18-20mph is a lot easier than overcoming the torque slap of a 25hp motor at 25-28mph. I used to let my wife operate my boat with the 15hp on it but now that I have a 30hp on it there is now way I will let her run the boat. It is just not safe for her given the inexperience and lack of upper body strength to overcome the torque of the engine. I have come very close in choppy water and high winds to losing control of my boat when running WOT...... and I am not a weak man by no means. The speed at which things can and do go wrong increase exponentially as horsepower and speed go up on a tiller motor. A steering wheel makes it far easier to overcome these dynamics given that you can have 2 hands on it and it is in front of you. And that is my 2 cents on the whole theory :mrgreen: 

Definition of "torque slap" (I made this term up FYI)...... The bigger the motor and faster you travel in the water the harder the motor wants to slap to the side or direction you aim it. Possibly causing you to lose control.


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## shawnfish (Jul 27, 2012)

Johny25 said:


> The two reasons I know of are weight distribution and torque of the motor. Console type boats usually have the console forward of where you would have to be to operate a tiller style motor. And really I have never seen a console as far back as to where you could run a tiller, although I am sure someone has probably made one like this. With the console and weight being further forward it changes the C of G of the boat for the operator. Take a full throttle turn at the helm of a console boat and then try one at the tiller position, a lot more force and chance to throw yourself out in the tiller seat.
> 
> Then you have the torque of the motor. Good example is a lot of tins are rated 15hp tiller but 25hp console. Overcoming the torque slap of a 15hp motor at say 18-20mph is a lot easier than overcoming the torque slap of a 25hp motor at 25-28mph. I used to let my wife operate my boat with the 15hp on it but now that I have a 30hp on it there is now way I will let her run the boat. It is just not safe for her given the inexperience and lack of upper body strength to overcome the torque of the engine. I have come very close in choppy water and high winds to losing control of my boat when running WOT...... and I am not a weak man by no means. The speed at which things can and do go wrong increase exponentially as horsepower and speed go up on a tiller motor. A steering wheel makes it far easier to overcome these dynamics given that you can have 2 hands on it and it is in front of you. And that is my 2 cents on the whole theory :mrgreen:
> 
> Definition of "torque slap" (I made this term up FYI)...... The bigger the motor and faster you travel in the water the harder the motor wants to slap to the side or direction you aim it. Possibly causing you to lose control.



good explanation!! and term! lol!


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## earl60446 (Jul 27, 2012)

Now that we have a name for it, "torque slap" can be pretty much nullified by moving that little rudder doohickey right above the prop and below the cavitation plate. I have mine adjusted to provide almost no "TS" when I am on plane moving about 22-26 mph, makes for a comfortable cruise and safer too. Keeping the side to side steering a little firm helps too, especially on a tiller.
Looked it up, "rudder doohickey" = trim tab
Tim


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## BLKLAB (Jul 27, 2012)

Johny25 said:


> Console type boats usually have the console forward of where you would have to be to operate a tiller style motor. And really I have never seen a console as far back as to where you could run a tiller, although I am sure someone has probably made one like this. With the console and weight being further forward it changes the C of G of the boat for the operator.



I can understand the weight distribution reason. However, I'm talking of jon boats where all they do is rivet a console to the side of the boat and you sit on the same bench that you would sit on to run the tiller. They put the remote steering in and now the boat is rated for an additional 20 HP. I dont understand the reasoning behind this?


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## earl60446 (Jul 27, 2012)

I glamed onto this from another blog although I have seen it on here before, might help to answer it.
Tim
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
The horsepower rating formula does not have anything to do with weight of the engine, speed , or whether the engine is a 2 stroke or 4 stroke. It also does not matter if the transom height is 20" or 25". There are two formula's....one for tiller boats and one for console boats. The formula that all boat builders use is from the American Boat and Yacht Council's book " Standards and Recommended Practices for Small Craft. The formula is as follows:
ABYC H-26 Powering of Boats
This is compliance of USCG regulations as stated in Title 33, CFR, Part 183, Subpart D.
Horsepower Calculations
Remote steering and at least a 20" transom.
LOA x Beam in decimal feet =_________ factor
Factor_____ x 2 =______ - 90=_____ horsepower factor

Tiller steering boats with at least 20" transom
LOA x Beam in decimal feet=_____factor
Fctor_____x .8=_____-25=______horsepower factor

Example: Console boat with a LOA of 19'3" and a beam of 97"
19.25 x 8.08 = 155.54 x 2 = 311.08 - 90 - 221.08
221.08 is the horsepower factor. The boat can be rated for 225 H.P. as explained in the following standard:
ABYC 26.6.1.2.4 If the horsepower factor as computed is not a multiple of 5, it may be raised to the next multiple of 5.
ABYC 26.6.2 The maximum horsepower capacity for boats 20' or more in length, recommended for use with outboard motors, shall be determined by the manufacturer and stated on the capacity plate.


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## Ictalurus (Jul 27, 2012)

earl

That doesn't seem right. My 1448 would be capable of a 40 HP tiller. (14' x 5.8 (70/12))*.8 = 64.96 - 25 = 39.96. Or better yet, a 75 HP remote. My boat is actually rated for a 25 HP, I think I've seen the formula that actually calculates those numbers, I'll see if I can dig it up over the weekend.


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## Johny25 (Jul 27, 2012)

earl60446 said:


> Now that we have a name for it, "torque slap" can be pretty much nullified by moving that little rudder doohickey right above the prop and below the cavitation plate. I have mine adjusted to provide almost no "TS" when I am on plane moving about 22-26 mph, makes for a comfortable cruise and safer too. Keeping the side to side steering a little firm helps too, especially on a tiller.
> Looked it up, "rudder doohickey" = trim tab
> Tim



Well you may have a new motor then because most tiller motor's 40 hp and under that I know of do not have trim tabs that move or trim tabs at all to counter the torque of the motor. 

And yes the formula you gave does not seem correct or I would be able to run a 40hp tiller on my boat, and there is no way that would be safe on any level. The 30hp tiller I have on there is already borderline stupidity and sketchy most of the time. My boat is rated 15hp tiller and 25 remote.



BLKLAB said:


> Johny25 said:
> 
> 
> > Console type boats usually have the console forward of where you would have to be to operate a tiller style motor. And really I have never seen a console as far back as to where you could run a tiller, although I am sure someone has probably made one like this. With the console and weight being further forward it changes the C of G of the boat for the operator.
> ...



Motor torque is the reason trust me. The steering wheel is much easier to operate than a tiller to the average person. Safety first is what the boat companies think of or else the lawsuits would be everywhere if they rated there boats with higher HP for tiller and remote.


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## TNtroller (Jul 27, 2012)

can someone explain to me how the gator guys in Swamp People have 90's, 115's, etc, and they are tillers??? They don't seem to have any trouble in handling the boats on plane, dont see 'em getting shook all to pieces either. :?


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## shawnfish (Jul 27, 2012)

TNtroller said:


> can someone explain to me how the gator guys in Swamp People have 90's, 115's, etc, and they are tillers??? They don't seem to have any trouble in handling the boats on plane, dont see 'em getting shook all to pieces either. :?



you beat me to it! lol!!! and troy stands and runs his....but he is king of the swamp!


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## Johny25 (Jul 28, 2012)

TNtroller said:


> can someone explain to me how the gator guys in Swamp People have 90's, 115's, etc, and they are tillers??? They don't seem to have any trouble in handling the boats on plane, dont see 'em getting shook all to pieces either. :?


 
The newer motors have hydraulic assisted steering on them, just like a power steering pump on vehicles. I was assuming that most of us are to damn poor to afford these motor's and that we were discussing what normal everyday tin boat fisherman use. I am sure that motor Troy is running was given to him at a great discount (or free!) just to get Mercs name out there on the show.

I'm not Troy and there ain't no swamp in my backyard :lol:


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## BLKLAB (Jul 28, 2012)

Mercury makes a big tiller setup. People are running 250 hp tillers on their lake boats. But yes Johny, I was talking about smaller tins that are rated for 15/25 or 45/65.


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## Zum (Jul 28, 2012)

I use(d)everything from a 2-60hp tiller.
Boats rated for a 35hp tiller;60 remote,I'm using a 30hp now,would go bigger but there alittle heavy to remove at the end of the season.
Heres a reply I stole from a walleye forum:

The CG formula to calculate the HP rating (remember the regs apply to boats under 20ft in length- the mfgs determine their own limits on 20+ boats but am sure their ins liability carriers undoubtedly have a big say) the formula is:

factor = width(in feet) x length then this "factor" determines the formula- to use- if the factor is more than 52.5, which is any boat more than 4' beam and 13' plus length; then formula is: 

(you can raise hp to next multiple of 5)

If boat has remote steer and at least 20" transom, (2 x Factor - 90 = HP) Exmple 18.3"

If no remote steer OR transom less than 20in,
(0.8 x Factor - 25 = HP)

Width is maximum transom width in feet excluding handles, attachments and extensions, If boat does not have a full transom, th transom width is the widest beam in the aftermost quarter length of the boat.

Example- Remote steer- 96" width(8') 18' 3" length
8 x 18.4 = 147.2 factor --- (2 x 147.2 -90 = 204.4hp) or rounded up to 210 HP but no 210 HP motors so set it at 200.

Tiller- Same size boat- (0.8 x 147.2 -25 = 92.76hp) or rounded up to 95hp no 95hp motors so 90 rating.


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## earl60446 (Jul 29, 2012)

Zum said:


> I use(d)everything from a 2-60hp tiller.
> Boats rated for a 35hp tiller;60 remote,I'm using a 30hp now,would go bigger but there alittle heavy to remove at the end of the season.
> Heres a reply I stole from a walleye forum:
> 
> ...


Looks to me like the same formula I posted above and people say is wrong.
Remember this is not an all encompassing formula to determine what _YOUR_ boat can handle, it is a formula to determine the maximum hp for a boat according to the CG. Not all 14 foot boats that are 4 ft wide are the same. I have seen 13ft boston whalers with 40hp motors on them and they handle it ok. My boat is rated for 60hp, I have a old 48hp on it (with a trim tab btw), my boat is 16.3ft and 7 ft wide but I have seen other boats of the approx same dimensions rated for much more.
Tim


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