Over hp rating

[gone_fishin]

I have a mid 80's 16ft alum springbok. currently has late 70's 40 merc. I bought and im installing a 1990 evinrude vro 90hp. Boat is rated at 60hp. Besides insurance what issues would i have putting that big a motor on my boat?(only weighs 40# more)

 

[smokeonthewater]

Re: Over hp rating

do a little search...... you can find dozens of times this question has been asked

 

[roscoe]

Re: Over hp rating

unsafe at most speeds.

illegal in many states, considered a willful violation which is an automatic guilty.

 

[5150abf]

Re: Over hp rating

Think of it this way, if you were rated to hold 40lbs over your head and then someone put 90lbs up there what would happen?

You would hold it for a while maybe but pretty quickly you would drop it hard, same with the boat, it may take it for a while but eventually the transom will fail and that normally happens at speed when the boat is under full power.

Now imagine a 90 horse engine full throttle not attached to anything.

You want to more than doulbe the designed load, very very dumb, if you actually do it make sure your life insurance is paid.

 

[tashasdaddy]

Re: Over hp rating

on inspection, you can be red tagged, sent to the trailer. accident, you are automatically guilty, unsafe boat. there are more and more reason. could end up homeless.

 

[Silvertip]

Re: Over hp rating

Engine weight is just one factor in over powering a boat. The boat must actually be able to handle a power increase of 50%.

 

[kenmyfam]

Re: Over hp rating

Don't do it. Many many reasons not to. Most important ones already stated.
My 2 cents.

 

[JB]

Re: Over hp rating

I have a mid 80's 16ft alum springbok. currently has late 70's 40 merc. I bought and im installing a 1990 evinrude vro 90hp. Boat is rated at 60hp. Besides insurance what issues would i have putting that big a motor on my boat?(only weighs 40# more)

You do mean if you survive, right?

You will have an extremely dangerous and terrible handling boat.

 

[Frank Acampora]

Re: Over hp rating

I am not against people overpowering a hull, as long as they do it logically and with respect toward others on the water--you don't buy a 427 HEMI and race it on the highway--especially if you have no high speed experience. Similarly, you would not take a stock overpowered hull and just smash the throttle. A little thought and work is in order first. Remember: the HEMI is in a Charger body designed to handle the power, not your grandmother's Alliance K car!

If you fully intend to do it no matter what, be aware that you will need to properly reinforce the transom to absorb the horsepower and thrust through the whole hull. The transom is not a stand alone part of the boat and other parts work in conjunction with it to handle horsepower.

With a good running Merc 90 on a 16 foot tin boat, you are looking at speeds up around 60-65 MPH which will be downright scary and outright dangerous in that hull if you don't know what you are doing. Probably outright dangerous even if you know what you are doing because it is such a light hull.

Again, If you intend to do it no matter what, send me your email address in a personal message and I will send some photos of my 14 foot flat bottom fiberglass with a 125 hung on the back. Note that this is not an everyday boat, I only use it when there is no traffic, and last season I did not use it at all.

The boat in the attached thumbnail is at about twice the rated horsepower and it will bite me in the a** with the slightest lapse of attention or operator error. But it's a fun ride while it lasts.

 

[Bondo]

Re: Over hp rating

I am not against people overpowering a hull, as long as they do it logically and with respect toward others on the water-- Probably outright dangerous even if you know what you are doing because it is such a light hull.

Ayuh,... I agree with Frank,... I too have been there, done that,+ just happened to Survive it...

That is a 61, Glastron Jet-Flite, rated for 60hp, with only an 80hp on it,...
It went on to be repowered with a 135hp....
If I live long enough,... It'll be reincarnated with the 150hp Tower of Power sitting on a stand in my garage...

 

[gone_fishin]

Re: Over hp rating

Thanks for all the replies. Im planning on reinforcing the transom and deffinatly going to do some test runs. Common sense might kick in at that point.If it feels too dangerous than ill get another motor. thanks again

 

[Silvertip]

Re: Over hp rating

Just curious, but why did you even bother asking about this? Seems to me you are hell bent on doing this anyway.

 

[tashasdaddy]

Re: Over hp rating

the last paragraph applies to most states.

The United States Coast Guard has an opinion on this frequently asked question, and their answer from their website is reproduced below:
Can I use a bigger motor on my boat than what it's rated for?
It is not a violation of Coast Guard regulations to install or use an engine larger than specified on the capacity label, but there may be state regulations prohibiting it, and restrictions from your own insurance company regarding this.
There are no Coast Guard regulations against exceeding the safe loading capacity, however, there may be State regulations or restrictions from your insurance company which prohibit this. There is a Coast Guard regulation that gives Coast Guard Boarding Officers the power to terminate the use of a boat (send it back to shore) if, in the judgment of the Boarding Officer, the boat is overloaded. There is no fine for this, unless the operator refuses the Boarding Officer's order. We certainly hope that you will abide by the rating, as overloading may lead to capsizing or swamping of the boat.
NOTE: The Coast Guard Capacity Information label is required only on monohull boats less than 20' in length. The label is not required on multi-hull boats, pontoon boats (catamarans), or on any sailboats, canoes, kayaks, or inflatable boats, regardless of length.
As the Coast Guard mentions, local regulations may apply. For example, in the state of Ohio one should be guided by this regulation:
Capacity Plates
(ORC 1547.39 & ORC 1547-40)
No person shall operate or permit operation of a watercraft in excess of any of the stated limits on the capacity plate. When no capacity plate exists, no person shall operate or permit operation of a watercraft if a reasonably prudent person would believe the total load aboard or the total horsepower of any motor or engine presents a risk of physical harm to persons or property

 

[Jeep Man]

Re: Over hp rating

Thanks for all the replies. Im planning on reinforcing the transom and deffinatly going to do some test runs. Common sense might kick in at that point.If it feels too dangerous than ill get another motor. thanks again

Don't think about it, get another motor. Using a 90 on that boat will be fun for that one time to say you done it. That one time would be under optimum conditions and when you have your guard up. To use this combo at times when you have other things on the go or when conditions can change would be a recipe for disaster.
When the inevitable happens, we will remember you by changing your handle to: "DONE FISHIN"

 

[BTMCB]

Re: Over hp rating

You have been politely but strongly advised by knowledgable folks (smarter than me) ALL in agreement. Should follow their sound advice.

 

[kenmyfam]

Re: Over hp rating

Just curious, but why did you even bother asking about this? Seems to me you are hell bent on doing this anyway.

Have to agree completely,

You can lead a horse to water !!!!

Now try to make it drink !!!

 

[renagade69]

Re: Over hp rating

The chances the boat was rated properly are pretty slim so I say go for it.

 

[a70eliminator]

Re: Over hp rating

I've watched and listened to this discussion countless times and something just dawned on me.
A guy takes a run of the mill 230hp V8, blueprints and builds everything from pan to carb with all "GO" parts and it dyno's 330hp for 100hp increase and you all say good job nice build.
I'm not condoning it just be respectfull and know the boats limitations, I have nothing to add in the legal dept. as I am currently guilty of this offence.

 

[Frank Acampora]

Re: Over hp rating

Well, 70: Even with autos, it is NEVER a question of just the engine! If the guy is serious enough to invest the money necessary to get the extra 100 horses from his V8, he is also going to invest in better wheels and tires, beef up the suspension, and maybe sub-frame connectors, allowing the car body the capablility of handling the extra ponies. However: If he goes drag racing on a crowded highway with it I'll be the first to call the troopers.

Same with the boat-- If someone adequately builds the hull to handle the horsepower I will say "Good job." If it is raced in a heavily traveled or congested area--that goes beyond negligence to criminal behavior. Worse than drunken boating or driving I.M.O.

So: if this guy is serious about hanging the 90 on his tin boat, I say OK, as long as he does it correctly and doesn't use it recklessly.

Here is my 14 footer with a 90 at 55 MPH. It started out life rated for about a 40. You don't want to know how many hours went into it so it can now handle the 125 it has hung on the back.

 

[Silvertip]

Re: Over hp rating

Case in point on the auto hop-ups: My nephew who just happens to be very engine savy and absolutley knows the in's and out's of nearly every vehicle on the planet bought a new Avalanche a couple years. Ago. Being old enough to have installed a small block Chevy into a Vega Coupe (as I am also guilty of twice when the car was just a couple years old) he decided he wanted a "sleeper "Avalanche". On goes a supercharger and low and behold this chunk of iron is now a virtual hot rod. Until one day the transmission main shaft said "I've taken enough of this abuse" and left him sitting at a traffic light. He has the truck towed to his local Chevy dealer because it's under warranty. Since there were no parts sticking out of the tranny the dealer obviously needed to see what was wrong so they removed the tranny and pulled it apart to inspect it. Yup - snapped main shaft. To my nephews dismay, GM refused to repair it because of the added super charger. I could go on with the long version but the end result of this was the statement that "I will never buy another GM vehicle". He now drives a Toyota. (Grin). So adding power to a car/truck is no different than adding power to a boat. People do it and some get away with it and some don't. If the tranny in this case was intended to be installed behind a blown mill it would have had the heavy duty main shaft and bigger clutch pack to handle that added power. As for my V8 Vega -- what a blast. I had people standing in line to buy that car when I decided to sell it. Then there is the little item called "brakes" that seems to be the last goody hot rodders install after a power boost.