Too big?

[forrestrmiller]

Hello, everyone. This is my first posting here, as I just joined. I just bought an Evinrude Sportwin 10, I think 57 or 58ish vintage judging by appearance. It also came with what I believe is a Sea KIng 5 hp (Eska built, I think). Is the Evinrude going to be too big for my 11' aluminum v-hull?

 

[Huron Angler]

Re: Too big?

What's the boat rated for?

It should be ok...but the boat could be rated for a 7.5 or less too.

Best thing to do is take it out and see if it's too heavy, too powerful or whatever. I have a 5.5hp on my 12' semi-V hull and in my opinion it would be fine with a 10, not that much heavier.

 

[CATransplant]

Re: Too big?

My 12' aluminum v-hull boat is rated for 10 hp. But, it's a wide sort of 12' boat, with a 62" beam. I haven't had a 10 on it, but wish I did sometimes. Still, I imagine that it'd take a little more delicate hand on the tiller than with the 6hp I have on there now. It just barely planes that boat at about 12 mph.

I'm betting that your 11' boat is rated for 7.5 hp. But, if you can give the name of the maker or the info from the capacity tag, we'll figure it out.

 

[forrestrmiller]

Re: Too big?

Thanks for the info, guys. I'm really not sure what it is rated at, or who the manufacturer is, because one of the former owners gave it a pretty rough camo paint job. There are still remnants of a sticker left on the side, but I havent yet been able to decipher what it used to say. I think it is also more of a semi-v hull design, too, as the bottom is mostly flat starting about 3' back from the bow, and it's about 16" deep at the stern. I'm afraid the sportwin may be too heavy for it.

 

[CATransplant]

Re: Too big?

Yeah, that sounds like a typical small aluminum boat. As for the 10 hp being too heavy...probably not. Too powerful? Maybe.

Some depends on how much you weigh. You'll be sitting back there working the tiller on that boat, so you add that weight and you may be a little low in the water. No way to tell without hanging it on there, putting it in the water and sitting down in the boat. You can put some other weight forward to even things out.

Now, for the power situation. From your description, I'd be willing to bet that the max hp for that boat is 7.5. You didn't say how wide the boat is. That'll make a big difference. Lots of the 12', narrow Alumacrafts, for example are rated only for a 7.5. However, if your boat is quite wide, that could be different. So measure it at the widest point.

If you overpower, weigh quite a bit, and push it, you could get in trouble with your little boat. Still, sensible people can manage if they aren't heavy-handed with the twist grip.

Get back to us with the width of the boat.

 

[Fisherball]

Re: Too big?

The formula provided in the regulations reduces to:

(2 X L X W) -90 = rated horsepower

Where:

L=boat length
W=transom width; if the boat does not have a full transom,
the transom width is the broadest beam in the
aftermost quarter length of the boat.

The rated horsepower may be rounded up to the nearest "5".
Here is an example of how the rating formula works in practice, applied to an older Boston Whaler boat, the V-20 model:

Boston Whaler V-20
Length = 19' 10"
Width = 7' 5"

Thus:

(19.83 x 7.42 x 2) - 90 = 204.15
Rounding up = 205 maximum rated horsepower

This is from Boston Whaler's site but it's the same formula that the State of Ohio uses.

 

[CATransplant]

Re: Too big?

Well, that formula doesn't really work for little aluminum fishing boats. When it says you can round up by 5, that's just silly. On a boat that figured at 7.5 hp, rounding up by 5 would make it 12.5 hp. That'd be too much.

For little aluminum fishing boats, it's a different story, really. Some 12' footers are rated for 10. Some are rated for 7.5. That's only 2.5 hp difference, but it's a 25% difference in horsepower. That can be huge.

Little narrow aluminum 12' boats are generally rated at 7.5. Wider ones are generally rated at 10hp. A 10 is too large for the narrow boats, and too heavy for comfort with an adult sitting in the tiller seat.

Most of these boats are designed first as row boats. They're not designed to be run at 20+ mph. They're not really safe at that speed. The idea is to come up with an outboard that just gets them on plane and not much more. They're not speedboats. They're dinky little fishing boats.

It's a whole other ballgame.

 

[Fisherball]

Re: Too big?

I had no idea about that but it makes sense.

 

[forrestrmiller]

Re: Too big?

Great information! I think my beam is about 44". That would probably put it in the narrow end of the spectrum. Transom is 16" high. Probably safe to say it's rated at 7.5. Did some horse trading for a mercury 6hp twin that will probably fit better. Thanks for all the help, guys!

 

[CATransplant]

Re: Too big?

Yah...I'm pretty sure you're rated only for 7.5, from the tags I've seen. The 6 is a good choice.