Why are outboard motors identified and regulated by HP?

[bassfisher444]

This is a question I have had for a long time but could never find a good answer to. Why is horsepower mainly what manufacturers, regulations, and laws go by when it comes to outboards and why is that unique to the outboard industry? Why does every outboard have to come with the hp rating label on it, or is it that even required, and why are boats with inboard motors not like that and exempt from HP regulations as well? In many cases it makes very little since to regulate, and advertize them that way. Why not go by displacement instead like ever other motor industry? Does anyone know the history of how it came to be this way?

[Transom]

That is a good question. I never understood that either.

[1781ccT]

I bet it has something to do with the transom. And needing to statistically factor in the IQ bell curve. The lowest common denominator for the latter is set to about 70 with the latter, imo

[BigFishSteve]

God’s plan.

[wareagle24]

I've wondered that too. I wish that I had an answer to it.

[bassfisher444]

I bet it has something to do with the transom. And needing to statistically factor in the IQ bell curve. The lowest common denominator for the latter is set to about 70 with the latter, imo

For the transom some 200 hp motors weigh 400 lbs and some weigh 600lbs yet they are still 200s even though the heavier one would put 50% more stress on the transom. For the IQ thing, it's illegal to put a 250 hp outboard on a 19 foot boat, yet you can have a 19 foot boat with a 500 hp big block inboard or better yet a 300hp Jet ski and it's perfectly legal. Both of those are good examples of why regulating them by HP doesn't make much sense.

[tcesni]

The motors aren’t regulated by hp but the boats typically sold for recreational purposes are. Why would you simply go by displacement? You certainly wouldn’t do that for a car engine, why do so for an outboard? A 75, 90 and 115 Merc have the same displacement.

[Mcjenson]

If you went by displacement guys would have little 4 cylinder twin turbos that are massively overpowered for the size of the boat. Horsepower isn’t perfect for boat rating, but it’s not terrible either.

[ssmithboats]

it was to keep the citizens from taking a 16 ft boat an putting a 300 hp motor on it .

[c rig]

it was to keep the citizens from taking a 16 ft boat an putting a 300 hp motor on it .

Well, technically, you can. I’ve known lots of guys with “overpowered” boats, based on the Coast Guard plate.

[bassfisher444]

The motors aren’t regulated by hp but the boats typically sold for recreational purposes are. Why would you simply go by displacement? You certainly wouldn’t do that for a car engine, why do so for an outboard? A 75, 90 and 115 Merc have the same displacement.

Vehicle engines are identified by displacement. When someone asks you what engine you have or you go to look up parts you go by the displacement not how much HP it has. Jet skis and inboard boats arent regulated by HP so why are only outboards? You are right the 75-115 Mercs are the same displacement, so why limit it to a 75 when you can have a 115 with the same motor?

[bassfisher444]

If you went by displacement guys would have little 4 cylinder twin turbos that are massively overpowered for the size of the boat. Horsepower isn’t perfect for boat rating, but it’s not terrible either.

Why is a 300hp outboard considered overpowered for a 19' boat, yet it's ok for the same size boat with an inboard or a much smaller jet ski? Compared to every else there is very little logic in rating outboards the way that they do.

[novakevlar]

Trolling motors - rater by power output.

Airplane engines - power output.

Electric generators - power output.

Batteries - power output.



Not sure why this is even a question.

[1781ccT]

If I make a your mom joke, do you promise to think it’s about somebody else’s mom? Great!

aimed at nobody in particular, but you wanna know what else is rated by their output? Your mom.

[bassfisher444]

Trolling motors - rater by power output.

Airplane engines - power output.

Electric generators - power output.

Batteries - power output.



Not sure why this is even a question.

What is the legal HP limit on those?

[brnzbaklvr]

Most all small engines for Lawnmowers are rated by HP..Alot of Farm equipment is also.

[av]

I don't see the mystery

[bassfisher444]

Most all small engines for Lawnmowers are rated by HP..Alot of Farm equipment is also.

Is there a limit to how much HP a lawn mower or tractor can have?

[WranglerSS]

It is so tournament directors can discriminate against someone running a 300HP outboard on a boat that is has a capacity plate for a 300.

[Mcjenson]

Why is a 300hp outboard considered overpowered for a 19' boat, yet it's ok for the same size boat with an inboard or a much smaller jet ski? Compared to every else there is very little logic in rating outboards the way that they do.

Weight distribution from hanging off the back?