Larger Outboard

I know outboard size rating are put on the boat for safety reasons, but i was wondering if anyone had any thought on the subject or first had experience. I have a 13' meyers with an 18hp johnson on it right now. I have the option to get a 25hp. The catch is the boat is only rated for a 15hp. I'm a bigger guy and with two people in the boat the motor just doesn't seem to have the umph to plane out. Anyone got any advice?

Don't do it, you're already overpowered. Your boat has limitations, don't try to excede them.

You are open to a whole bunch of liabilities when you overpower a boat and some states have laws against it, for a very good reason too.

Buy or trade for a bigger boat if you want to go faster with more weight.

Agreed. While you may not be cited for it, you have zero protection in the event there is an incident and you are taken to court for personal injury. It's just not woth the risk. That being said, I see a lot of boats on the water that are overpowered. I just think compliance is the best safety net.

I have a 25hp motor on a 1436 jon. The boat is probably rated at 15hp and is really 13'6" long. You will find several of us on here running 25 motors on boats about 14' long.

I'm running 25hp on a 14' mirrocraft v-hull.

Have you thought about getting a stingray jr hydrofoil?

And possibly some trim tabs to get more lift?

Also jet ski's use sponsons and they work great, a set of them properly placed and angled will produce a TON of lift. I would put them about a foot infront of the transom and four or five inches up on a slight slant to produce lift and get out of the water when you reach plane. 20 degrees should be more than enough tilt back.

Fishin_Rev said:

I have a 13' meyers with an 18hp johnson on it right now ... I'm a bigger guy and with two people in the boat the motor just doesn't seem to have the umph to plane out.

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what's the rated weight capacity for the boat? 18 hp johnson is like 80#... 25 hp motors are like 150# minimum. you said you are a big guy, are you sure you wouldn't be/aren't already overloading the boat? that's a lot more dangerous than overpowering it is.

My 1983 25hp Mariner built by Yamaha weighs 105lb's. You can also re-distribute the weight in the boat.

Fishin_Rev said:

I know outboard size rating are put on the boat for safety reasons, but i was wondering if anyone had any thought on the subject or first had experience. I have a 13' meyers with an 18hp johnson on it right now. I have the option to get a 25hp. The catch is the boat is only rated for a 15hp. I'm a bigger guy and with two people in the boat the motor just doesn't seem to have the umph to plane out. Anyone got any advice?

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I would think an 18 horse engine would plane out a 13' boat. Maybe you need to shift some weight forward or do some tuneup work on the motor?

I will look into the hydrofoil i talk to some people today who also suggested that. As for to much weight in the boat i am still under the capacity for the boat with two people and gear. With just me in the boat it planes out fine the problem is when i have two people it doesn't want to plane. I am also going to try moving the gas tank and see if that will help. The motor could use a tune up but right now the money isn't there to do it. I had mechanic friend check the compression and i had 110 on the top cylinder and 107 on the bottom. I just put new plugs in and am going to try changing the angle on the motor by moving the pin.

Motor all the way down for power should help with the 2 other people.

i put a 25 on my old 12' v hull and it scared the crap out of me.waaay too much motor.

I have a 68' Evinrude 18hp on a 14 footer. The boat is rated for a 20 hp. With my mods and two people I plane out just fine.(both with a hydrofoil and without) I think it might have something to do with your motor. So far the top speed I have reached has been 16mph with me and my girlfriend on the gps. I may be mistaken but I think I read somewhere that the older outboards measured the HP at the motor and not at the prop like modern outboards. So an 18hp motor may not put out the full 18hp at the prop like you would think closer to a modern 15. But I'm not saying a 25hp would be safe either. Play with the trim settings on your current motor... move some weight around... and possibly look into a hydrofoil... because your current motor should do the trick.

i am for sure going to look into the hyrofoil, i am going to take the boat out on sunday and try different setting on the motor.

hp ratings are for out of the factory boats. if you reinforce the boat like beefing up the transom and gusset/knees, it should allow the safe use of motors slightly over the rated HP. by how much, there's no telling for sure.......

as it is, you already have too much motor for your boat. a 13 footer should be flying even with a 15hp. perhaps you need to take a look at the trim or prop.....

J.P. said:

hp ratings are for out of the factory boats. if you reinforce the boat like beefing up the transom and gusset/knees, it should allow the safe use of motors slightly over the rated HP. by how much, there's no telling for sure.......

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while that seems to makes perfect sense, the coast guard disagrees. the only things taken under consideration when calculating the maximum power for boats under 20' are the length of the vessel, the width of the transom, and whether or not it has flat bottom/hard chines or a 20"+ transom and remote steering.

sturdiness of build, etc. does not enter into it. the formula is designed to keep people from putting too heavy of a motor on a small boat.