How do i figure out what my boat is rated for?

[iknowyoulike]

I have a 14ft 1964 Mirrorcraft aluminum boat that use to have a 6hp motor on it and that thing was just to slow on bigger lakes but recently upgraded to a 20 hp merc. I'm wondering if that's gonna be overkill for the boat or am i just paranoid. I haven't taken it out on the lake yet either so before i do i want to get some feedback about what i just did.

For future reference how do you figure out what a boat can handle or take for an outboard as far as HP rating goes...is there a rule of thumb that you guys follow? my boat doesn't have any stickers or marking to tell me what the max is.

[Meat-Run]

FYI, I have a 14ft boat shallow model in the early 70's and I have a 20hp Johnson on the back. It's not to much power as long as the transom isn't flexing you should be ok.

mr

[Ufatz]

You are probably at, or close to, the limit for your boat. But you are doing the right thing by asking people about it, since there are no markings on the boat. The horsepower rating involves many factors, length being just ONE of them. Hull design, material used, floatation, hull rigidity and other aspects of the boats construction go into developing the horsepower rating. I'm guessing your 20 Merc will be just fine. Have fun.

[dkhntr]

I dont know, I had a old Alumacraft F7 that the rating sticker said either 12 or 15 hp. Cant remember which. Keep that in mind. But because your boat is old enough to not have a plate, I would use your 20 and play dumb. My F7's transom was strong enough to support a 23 horse mud motor (200 lbs) it flexed a little bit.

[iknowyoulike]

so say that i did get an over rated motor for the boat what's the worst that can happen? i'm planning to take this up to Birch lake in Babbit next week and want to make sure it's okay first.

Is there a way to replace the old wood on the transom out with new materials? is there any special way of doing it or is it just a matter of taking the 4 bolts out and measuring the wood and cutting new pieces..? thanks for all the great replies.

[Ralph Wiggum]

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so say that i did get an over rated motor for the boat what's the worst that can happen? i'm planning to take this up to Birch lake in Babbit next week and want to make sure it's okay first.

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You could rip your transom off.

[Ufatz]

Just take it easy. No full throttle "hole shot"nonsense. Gentle acceleration. Sure, keep an eye on your transom for flexing or other signs of strain. Otherwise, make your trip,catch lots of fish, keep a few and have a good time.

[iknowyoulike]

Is there anything i can do to make the transom stronger?

[Valv]

Yes, check this out:

http://www.fishingminnesota.com/forum/showflat.php?Cat=&Number=1092726&page=0&view=collapsed&sb=5&o=&fpart=1

That's exactly what you need and you won't find it anywhere else.

[pfluemis]

Quote:

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I have a 14ft 1964 Mirrorcraft aluminum boat that use to have a 6hp motor on it and that thing was just to slow on bigger lakes but recently upgraded to a 20 hp merc. I'm wondering if that's gonna be overkill for the boat or am i just paranoid. I haven't taken it out on the lake yet either so before i do i want to get some feedback about what i just did.

For future reference how do you figure out what a boat can handle or take for an outboard as far as HP rating goes...is there a rule of thumb that you guys follow? my boat doesn't have any stickers or marking to tell me what the max is.

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Take EXACT measurements of your boat and compare them the the EXACT same boat new. The HP rating will be the same.

As an example, if the boat is 14' long, has a flat bottom, a 60 inch transom width, a 26 inch bow depth, and a 61 inch beam width, the boat can only handle a 15 hp motor. This, compared to a 14' boat with a flat bottom, 63" transom width, 68" beam width, 30 inch bow depth, can handle a 25 hp motor. Now if the second boat was a V bottom, it could handle 35 hp. All above boats are a standard bench seat fishing boats. Take the measurements and search the Mirrocraft, Lund, Alumacraft, Crestliner, ect.. websites and find the boat that matches what you have, or as close as you can get.

The measurements are as follows:

Beam: The widest part of the top of the gunwales.

Transom: The BOTTOM of the transom, just before it starts to curve down to the bottom of the boat. Basically where the waterline would be in an empty boat (with motor). Sometimes called the "footprint".

Length: From the center of the back of the transom, to the tip of the bow.

Overpowering a light boat can be very dangerous. Going 10-20 hp over on a 1500lb boat might not cause problems, going 5-10 hp over on a 225lb boat is literally an accident waiting to happen.

[Ufatz]

Man you are gonna be right on the edge for that light little boat. Be careful. Put some weight in the bow for your first trail run and then throttle up slowly.