Motor size when boat tag says what size it calls for?

My boat says on tag rated for 100 HP, So can you put a bigger motor like a 140 HP? Is this a insurance thing or will a gamewarden give a ticket for over
powering the boat.

Re: Motor size when boat tag says what size it calls for?

There are many things to consider when thinking about overpowering a boat. Something to think about:
- Liability insurance - you may not be able to get it.
- If you have an accident, if you are overpowered, and the plate on the boat proves it, in a court of law it might be proof that you knew or should have known you are overpowering the boat, and this will cost you in court.
- Very likely you will be giving more horsepower than that hull was designed to handle. This may lead to handling problems itself.
- Overpowering a boat may mean that you are putting more weight on the transom than it is designed for. This may also be a problem with 4s engines.
- As a general rule, it is more dangerous to overpower a boat than to underpower it.....

just a thought.........

Re: Motor size when boat tag says what size it calls for?

Hmmm, good question. I don't recall ever having the Water Patrol check the HP of the motor vs the boat tag. With my limited knowledge I would assume it is a weight to power thing. Too much weight or power being a bad thing in this case. I know my father once had a 235 Mercury ( I think that was the OB motor) on an 18 ft Champion that was only rated for 150 HP. (I'm working from old memory here, I might have sizes wrong) In any case, it was a short-lived accident waiting for a place to happen, as the Champions are rear weighted to begin with, and launch almost straight up. It did not take him long to make a downsized trade.

Re: Motor size when boat tag says what size it calls for?

txmntman said:

- Very likely you will be giving more horsepower than that hull was designed to handle. This may lead to handling problems itself.
- Overpowering a boat may mean that you are putting more weight on the transom than it is designed for. This may also be a problem with 4s engines.

Click to expand...

I agree. I wouldn't try it. Not saying you would be given a ticket, but you would be wrisking your life.

Re: Motor size when boat tag says what size it calls for?

Ok I see thanks, It has a 100HP on it that came on it new a merc, I'm replaceing it with a 85 evinrude and fill it will be just fine.Just I see 115's and 135's 4 sale and was only thinking of useing one of them.Thanks for your help here.

Re: Motor size when boat tag says what size it calls for?

I have a 1967 Starcraft with a hp rating of 120hp, it came to me with a good running 135hp. The way I see it is that if I were to buy a new motor, at 120 hp, I'd be increasing the weight and not reducing the hp any. After 1984 they began to rate motor hp differently, they rate the newer motors at the prop vs at the motor, so in reality, a new 120hp which would be a legal motor according to my coast guard plate, would still most likely be stronger and heavier than the 135 on it now. If I replaced it with an older motor, say a 120hp, I'd not save any weight, being that both are V4 motors with the same weight give or take a few pounds, I'd have only made the change for the HP rating alone.
For now, I leave it alone, I did buy a newer 115 for it but it's 100 pounds heavier than anything back in the day and probably far more powerful overall.

I'd run the motor on it if it's in the same motor family as the rated maximum motor. Take the boats rating into account when driving it. I'd rather be a bit overpowered than underpowered any day.

I've never had the CG or Marine police check motor size or rating. Most don't even pay any attention to anything beyond the registration number and whether or not you have the correct license and certification to be driving.

Re: Motor size when boat tag says what size it calls for?

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

Re: Motor size when boat tag says what size it calls for?

It isn't as much of an issue of the water patrol or coast guard folks checking for this as it is the fall out from an accident. In that scenario you have an attorney or two or three, insurance companies, local law enforcement and perhaps others looking at all aspects of the accident. On an over powered boat you know who will win in court. And don't lie on your insurance application. That insurance company will hang you out to dry when they determine you lied about the over power issue.

Re: Motor size when boat tag says what size it calls for?

Well I've learned alot asking this so again thanks guys, You all have a great
Christmas,

Re: Motor size when boat tag says what size it calls for?

My boat is rated for an 85 and I have an 88HP engine on it. Talked to the insurance people before doing it and they gave me a written waiver. Seems they will look the other way on a little over, but not a lot over ...

Re: Motor size when boat tag says what size it calls for?

TD's post pretty much agrees with what I said about sticking with the same engine family in a particular motor family. For instance if a boat came with a Johnson V4 2 stroke, say a 90HP and is rated at only 100hp max, then running a 140 hp Johnson V4 will not add any weight or affect the handling of the boat by way of weight distribution. Doing so on a very short boat will no doubt affect it's handling and could indeed be unsafe, but if run by a responsible individual who knows the limitations of his boat, it should be just fine.

Myself, I try not to own anything that I have to insure, I've never had boat insurance and quite frankly don't know anyone that does around here.
It's not required and if it was, I'd probably have to park the boat. I pay way too much to insurance companies now in this state, there's no way I'd be able to afford any more. It would no doubt put an end to any multiple boats.
Besides, only one of my boats actually has a Coast Guard plate on it, and that boat will never see a gas motor since they are not allowed here in freshwater.

Where you would run into trouble would be taking a boat that say has a max hp rating of 50 or so hp, and hanging a huge 200hp V6, while it might be fun, it would no doubt pose all sorts of risks, besides simply sinking from the weight of the motor.
A few years back I had an old 25hp Johnson that I wanted to test run, but had only a 12' jon boat handy, that was the wildest ride I've ever had in a boat but there was pretty much no stopping since the stern was only 1/2" from taking on water and the act of simply slowing down would bring water in the back of the boat. It would have been a lot better if it weren't a tiller motor and I could have been at the other end of the boat to balance the whole rig out.

Re: Motor size when boat tag says what size it calls for?

The USCG mandated capacity plates have to do with weight, not really HP.

They chose to list it by HP because the vast majority of boat owners have no idea what their engine weighs. When the 4 strokes first came out this led to some minor issues with some small boats (we're talking 12-14 footers here) especially the low freeboard 15" transom types as the early 4 strokes were vey heavy for their HP rating.

I personally know of a fellow that nearly swamped his boat reversing it....

Obviously that has changed in the past 10yrs or so as those motors have gotten considerably lighter.

Re: Motor size when boat tag says what size it calls for?

kaferhaus said:

The USCG mandated capacity plates have to do with weight, not really HP.

They chose to list it by HP because the vast majority of boat owners have no idea what their engine weighs. When the 4 strokes first came out this led to some minor issues with some small boats (we're talking 12-14 footers here) especially the low freeboard 15" transom types as the early 4 strokes were vey heavy for their HP rating.

I personally know of a fellow that nearly swamped his boat reversing it....

Obviously that has changed in the past 10yrs or so as those motors have gotten considerably lighter.

Click to expand...

That makes a lot of sense since most transoms are all pretty similar in design. Pretty much if the boat will hold the weight, it pretty much will handle the power.
The 2 vs 4 stroke weight issue comes up a lot when repowering older boats. Especially on smaller boats rated at the edge of their weight limit so to speak.

A good example of smaller boats and 4 strokes is my 12' aluminum boat, it's rated at 10hp max and has a 15' transom. Since most 2 stroke 9.9 and 15hp motors are the same family and weight, I've run a rebadged 15hp on mine for years. I have a 10hp Honda 4 stroke from the mid 80's which is far too heavy to hang on that boat. It almost sinks the boat. The weight is nearly double that of my Johnson 15hp 2 stroke. In fact, it's not much lighter than my 25hp Johnson 2 stroke. That motor don't get much use since there's not much that can tolerate the additional weight in the stern. Power wise, it's also not as strong as the Johnson 2 stroke but its far better on gas.

Re: Motor size when boat tag says what size it calls for?

some people stick within the borders some dont me being one of them.
hull type has a lot to do with what ya use if over on the hp ,
i have a 175 on my mckee craft,its rated at 140 im currently trying to find 140 looper to build and mod ,keeping the horsepower at around 150 or so and loosing some weight ,but my hull is capable of holding the weight and power of the v6,have been stopped bunches never questioned ,but in south louisiana
we have bateauxs with 150s on im ,but its probaly best to stay in the guide lines of producer of boat,

Re: Motor size when boat tag says what size it calls for?

With small block chevies nobody can tell without removing the engine and doing a dyno.