Another overpowering discussion

[bonz_d]

Yes I know this comes up all the time and has almost been beatin to death but I have a question that I don't recall ever being brought up or if it has I've missed it.
I fully understand the reasoning and arguements and agree with why it should not be done but this thought just came to me while looking at a used boat that is w/o and engine.


The boat in question is rated for a max of 40hp. It is also a side steer console boat. So the question is this, over the years OMC made a family of engines ranging from 40hp to 60hp all based on the same format, frame, design. Basically all the same engine with differing hp ratings. I know they did the same with the V4's

So with the weight factor/frame being the same for these engines why would the hp rating of these engines make that big of a difference. In this case a max rating of 40hp when the 50, 55 and 60hp are again basically the same engine. Case in point, I have a 16' Alumacraft that is rated for a 75hp max. Currantly have a 60hp 2 cylinder on it and really haven't seen any performance differeance with a 50hp 2 cylinder on it. Yet I'm sure I would see one if I went from the 60hp to a 40hp.

 

[southkogs]

I had a 15' fiberglass runabout rated for 100HP. We ran a Evinrude 65HP (3cly - essentially what is now the 70HP) for years, and for a couple of years I wound up having a 50HP (2cyl) on it. With a 65HP, she was a 30 MPH boat and would pull three skiers (on two skis, could only easily pull one up on slalom). With a 50HP, she wouldn't even come up on plane with just one person on board.

When it boils down to it, as far as the hull goes; stability and strength would probably be the two factors. Some transoms would handle a buncha' extra HP and others won't. Some have a hull that will still be (relatively) stable with a buncha' extra HP and others won't. I would think some of the HP ratings are based on "best performance" for the boat design, and some take in a "lowest common denominator" operator consideration.

 

[bonz_d]

I can understand underpowering as a common practice for many reasons. Purchase cost, size of the waters it's used on, as on. In the case of my Alumacraft it does just fine with a 60hp 2 cyl. yet in my opinion would be scary with a maxed out 75hp. The poat really does not need that much power. While the Lund S14 DLX with a side console does very well with the maxed out 35hp on it.

The boat I was looking at in another tinny. A 1985 Mirrocraft and as I said is rated for a 40hp. Yet in 1985 OMC produced a 40, 50, 55 and 60hp version of the same engine So I cannot understand why a manf. would build a boat only rated for the low end of that power spectrum. As all of those engines are carring the same weight.

I guess I just don't understand how 10 more hp would have that big of an effect as in going from 40 hp up to 50 hp using the 40 and 50hp OMC as an example. At this same time period Lund produced the Pike 16D which is the same class in size, design and overall weight yet they built tat boat to be rated at 50hp which makes more sense.

 

[southkogs]

Think of it in terms of percentage: Going from a 9.9 to a 15HP is an increase of 50% available power. From a 50HP to a 60HP, it's a 20% increase. From a 100 to a 110HP, that's only (about) 10%. A 10% overpowering is going to feel substantially different on a given hull than a 50% overpowering.

That's not a perfect example, but you get the idea.

We have a 14' rowboat/fishing boat that we run a 9.9 on. We pulled the 15HP from our pontoon and tossed it on that boat for fun one day ... scared the tar outta' us on the water. Limped it back to the pier and put the 9.9 back on. 5HP on that hull (50% increase) was crazy. I could put another 20 HP on my current boat (not easily as it's an I/O) and it would probably be barely noticeable.

 

[bonz_d]

Guess I am looking at it more from a power to weight ratio thing than a percentage increase. Of the engines in the OMC family of that year,40,50,60hp, the 40hp has the worst power to weight ratio. Then if one were to drop down to the 30hp model it even has a better ratio than the 40hp. Then in that year Mercury didn't even build a 40hp model, they had a 35hp and a 50hp. Only Mariner, Yamaha and OMC produced a 40hp model in 1985 and I don't recall seeing many Yamaha's running around back then.

 

[Frank Acampora]

It has NOTHING to do with engine size or weight and everything to do with being an outboard powered hull. If you had a hull which was rated for say 1000 pounds total weight including engine and if this hull could support a 750 pound outboard, then with one 150 pound driver you would still be "legal" The Coast guard does not care how you distribute maximum weight.

. Coast Guard has formulae to determine the weight bearing capacity of a given hull and its horsepower rating. These formulae take into account a whole host of factors including transom depth and width, hull size and beam, total freeboard. type of hull, and type of steering. The manufacturer builds its hull and uses CG formula to determine horsepower and weight, then certifies that the hull meets CG standards and affixes the sticker to production models.

In fact, no where in the PA regs does it say that it is illegal to overpower a boat and recently the requirement for all hulls to have a capacity plate has beed dropped.. The Gendarmes CAN stop you and confiscate the boat for being manifestly unsafe though---the Law always has the advantage.

NOW: To complicate matters, this is applicable only to outboards and pleasure craft. Racing and specialty purpose boats are exempt as are inboard/outdrive hulls. In fact, The little 10 foot Cougar Cub, Invader, and other personal mini boats like it are also exempt with the proviso that in no case are they to be powered with more than 40 HP. They are tested over a fixed course until the hull gets unstable and that horsepower if less than or equal to 40 horsepower is allowed.

I/O hulls have no horsepower restrictions and you can put a big blown Chevy 454 in a 15 or 16 foot hull.

So, if you want to "overpower" your hull, with a larger engine of the same weight class it is your decision but be aware that there can be consequences to your actions.

 

[bonz_d]

Thanks Frank but as I stated in my 1st post I already understand all that. I guess what it all comes down to is I'm trying to figure out why Mirro would build this boat with that hp rating during that year or the years that model was produced knowing the outboards that were also produced during that time frame. From what I know of Lunds and Alumacrafts that class size boat all had a 50hp rating. It just seems that this is an odd ball and during that period the engine of choice for those sized boats were either 35hp or 50hp or in the case of the heavier Lunds and Alumacrafts the 16' went all the way up to a 75hp rating.

 

[roscoe]

Its all about what the manufacturer determines is an appropriate engine size for safe operation, and for the integrity of the hull and transom.
It could also be that the same exact hull is only rated for 30, or 35 hp in the tiller version, again, safe operation limit for hull shape and handling characteristics.
Now add that the competition may have a similar boat, rated for 40 or 45 hp, and they may have bumped the rating up so they were more competative.

Mercury has made a 40 hp model from 1972 - 2004, 2 cylinder. It was Belgian made, distributed around the world, and imported to the US in several markets/ years.

 

[bonz_d]

Mercury has made a 40 hp model from 1972 - 2004, 2 cylinder. It was Belgian made, distributed around the world, and imported to the US in several markets/ years.

A search here; http://boatspecs.iboats.com/Engines/bpe/10 is where I looked for info on the Mercs and from the little I know about Mercury is that there was a 402 which was actually a 35hp.

 

[bonz_d]

Thanks everyone for your thoughts and input. Makes me wonder if manybe the CC/Manufacture HP rating plates are outdated, especially with the introduction of the new 4 stroke engines.

Trust me I'm all for being safe on the water and seeing safe boats out there too.

I think the % thing is overrated as a guild because as pointed out the difference between a 6hp and an 8hp is over 30%, same with the 40hp to 55hp, same with 100hp to130hp, same with 200hp to 260hp.

Then again we can look at my 16' Alumacraft. it also is in a strange range from my view point. As it is, it is rigged with a 60hp 2cyl Johnson which I feel is maxed yet it is rated for a 75hp which I feel is overpowered. Unless the water is fully flat I rarely find myself running at full throttle. Also when fully loaded with max number of people I also still have no problem reaching plane. In my mind I aslo picture a huge difference between say a 60hp 2 cyl and a 3 or 4 cyl. 70/75hp. So as rated for a 75hp max even just going up to an 85hp which is what about 15%. This boat would be dangerous.

Anyways, while I was looking at this Mirrocraft my intention was to find a boat about the same size as my Alumacraft only lighter weight which would make it easier on me when fishing alone. I would have powered it with only a 35hp, again to reduce weight even though I have a nice unused 50hp Johnson parked in the garage. Which is what started this thought of why would they build this boat and then only rate it for a 40hp.

 

[Pony]

I agree it is odd that Mirrocraft wouldn't so something to the design to get rated for the extra 10hp....if nothing else to open up more rig combinations. It has to have WAY more to do with the hull design than anything else. Your Alumacraft is rated at 75hp....which if we are looking at Opti's, that block could get you 125hp. That would be crazy on that hull....same engine weight.

 

[roscoe]

You really will find no consistency between manufacturers or models when it comes to hp rating for boats made from 1960 through the mid eighties.

I have a 450# 1966 Starcraft that is rated for 75 hp.
Can you imagine putting a big early 60's omc 75 on her? I can't.

And I had a 400# Alumacraft rated for 65. It was crazy fast and almost uncontrollable with a 50 on her. It became manageable only after I added 300# to the bow.
A few model years later, the exact same boat was rated for 45hp.

As far as getting info from boat spec ................

 

[Frank Acampora]

Well, you are overthinking it and certainly using tunnel vision: You are not seeing the big picture. All you see is your hull and engine and what could be or why can't it be?

1 The hull manufacturer wants to build a hull for a certain market-say the 15 foot fisherman. All the manufacturer cares about is the hull type and size. At this point, he cares nothing about horsepower--except if he is designing a (for example) bass boat where there is definitely a horsepower race. So the hull is sketched, the designers get their say, and of course, the "bean counters" also get their input--remember manufacturing cost is always a deciding factor in design. The hull ultimately is built and certified for (again, for example) a 30 horsepower maximum. Now, at this point the manufacturer either doesn't know or care that OMC makes the same engine in 30, 40, 50, and 60 using all the same components, thus the engines all weigh approximately the same.

Now, this is not a hard and fast rule: I do remember one manufacturer who's hull was rated in a boating magazine. It was noted that several changes were made to the second year's production of an offshore hull so twin 275 HP outboards could be used instead of the original twin 250 HP the first year was rated to carry.

2. Now For example, OMC sees a market for engines sized 30-60 horsepower. Again, because manufacturing cost is of paramount importance, OMC designers decide to use the same basic castings for engines varied in size from 30 to 60 horsepower. This has economies of using only one set of casting dies, which can cost upward of 100,000 just to design and make, economy of inventory, because only one set of castings are maintained in inventory, economy of scale because they make 500,000 of the same basic engine instead of 100,000, economy of bookkeeping, and economy of training labor. ALL in all a good deal for OMC. No where do they care that all these engines weigh the same and thus COULD be put on the same hull rated for the smallest one with no real deleterious effects. ALL they care about is selling the most engines they can.

If you haven't realized it yet, MONEY rules any manufacturer the world round. If you don't make a product, you don't make any money. But on the other hand, if you do make a product, bean counters are up there, second only to manufacturing itself in importance.They exist to maximize, not minimize profit. And engine size versus hull size is never or almost never in the equation.

 

[Stumpalump]

Funny thing is I currently run a 16' tin boat (Valco Bayrunner) rated for a 50 and have that mid 80's 2cyl OMC on it. Mine is a 60hp. Mine is tuned, proped and set up to perfection and I have a ton of experience with boats. With that said my observation is that it's overpowered and I would not throw the keys to a new boater. It's jumpy, it could throw you out of the boat, at WOT and trimmed out the hull wants to lift and get unstable. That's only 37.5 mph. A 50 would tone it down and be easier and safer to drive and have no chance of reaching that speed where it's unstable. For the good of the general boating public a 50 is max. Hp ratings are just like the max weight ratings. You can stretch them but as soon as you do ugly characteristics become evident. Can you handle it or better yet do you want to deal with the adverse effects? That's up too you. Overpowered boats are nothing to carelessly fool with. My 60 has my utmost respect at all times. The mid 80's 60 is the same powerhead used on the OMC racing SST class. Only difference is holes drilled in the rod ends for better oiling. Race rods are solid but must run 25:1 oil. They are light, underrated, peaky little runners and may be why mine is obviously overpowered. One of the best kept secrets in outboards is the 2cyl 60.

 

[bonz_d]

Well I must be operating with the same tunnel vision that Mirro had back in 1985 as I am sure OMC or Mercurey probably manufactured and sold more 50hp engines than Mirro produced boats. Which is probably why Mirro fell behind in boat sales at that time and then became Northport which then became Northwood which is now back to Mirrocraft. Their tunnel vision couldn't compete with any of the 16' Fishing/utility of the 1980's. Yet look back to the early 60's to the mid 70's and Mirrocraft was a big seller in this area of the country for 12' to 16' boats. As a matter of fact the boat I was looking at was basically the same hull that they produced during the 60's and 70's. Which thinking about it probably accounts for the hp rating they have.

So you are trying to tell me that a boat builder is going to design and build a boat w/o any consideration for what powerplants are available. No market research? I would call that pretty short sighted. That would be like me going into the computer building business and only making desktops when everyone wants a handheld. Or would be like putting a 6 cylinder into a full size stationwagon because we want this size yet we want the economy of a 6 cylinder.

So I guess Mirro didn't see the "Big Picture" either. And as for engine size for OMC, because that is what I am familiar with, the 40,50 and 60 were the same family. The 30hp is a different family/size/weight/design. So again if you want to build to the 30hp size family why rate it for 40hp when practically none in that size exsist?

 

[Frank Acampora]

Well, the manufacturers are not stupid and for example a bass boat IS going to be designed to carry the maximum horsepower it can. In fact, you see bass boat ratings all over the place: I recently sold a 90 to a guy with a little and I do stress little Skeeter. I couldn't believe it was rated for 90 until I found the capacity plate.

Back to discussion the manufacturer knows an approximate horsepower rating a hull he is designing will carry but probably not the exact rating. And as for Mirro-craft--everyone makes marketing mistakes: Remember the Edsel? No, you are too young? Ford's biggest flop. Remember the AMC Pacer? AMC was bought out by Chrysler after that fiasco. Betamax? 10 inch lazer discs? Need I go on?

Actually, Bonz I really don't understand what you originally were asking anymore: You say you already know everything.

I say that the CG has formulated horsepower ratings for reasons I don't fully understand and perhaps no one ever will. BUT there was a reason originally. I say just go with it unless you are wanting to make a go fast that will surprise everyone on the water and possibly get the attention of the local water police.

 

[bonz_d]

Yeah Bass boats are a whole different animal, sometimes I wonder how they stay afloat.

Frank I'm not as young as you may think. A neighbor of ours bought one of those Edsels when I was in grade school. He sure was proud of that car!.

Well I don't know everything and never claimed to. Though being here on this forum daily I have read all the arguements on this subject and have read more on regs. online. I guess the question after thinking about it would be not so much the boat but the engines. As a comparison use the 50 and 55hp OMC or the 50 and 55hp Merc which are basically the same engines only tuned different or they are the same engine only rated differently. How much actual power differeance is there between those two examples. Enough to make a differeance?

I can agree that there would probably be enough of a differeance that it would be noticed while coming up to a lane between the 40hp version of the OMC when compared to the 50hp version when mounted on the same hull with the same load but I really do not think you would see any differeance on the top end.

As you yourself knows with these smaller hulls weight load has a much bigger effect on performance than a small power increase or decrease.