Engine size vs. Boat size

[Floater]

First things first. I love this site. I found it by following up a story in the paper and I find myself checking in everyday. The weather, stories, pictures, advice, whoa. I love the graphics too. I too having been lurking in the shallows for awhile. Sorry, couldn't resist. As the name says I float around, Hagg, Tillamook, Charelston, St. Paul, Ocheco, Prineville, Newport, Clackamas, Santiam, Wilsonville ponds, etc. Anyhoo, I'd like to post my first question if that's ok. What's the standard for outboard engine size vs. boat size? Is there a written or unwritten rule for weight or length? Smaller boats seem to go with 1hp or 2hp per foot. 18 footers and larger seem to go with 3-5hp per foot. What about kickers? With a 21ft alum boat, my 6hp 'rude moves it in calm water but I haven't tried it yet in the faster stuff. Again, love the site Jennie. [img]images/icons/smile.gif[/img]

[FishinMission]

Well...I think most boats have a Coast Guard "Maximum Capacity/Horsepower" tag somewhere on them....usually near the transom. You should get a few responses here tho from other members. Myself...I have a 21 foot sled...200 Merc pump. My kicker is a 15 Merc. Most go with a smaller kicker like an 8 or 10 h.p....but I stuck with the 15 for a little extra "zip" and throttle response when needed. Works great for me...Others??

[sturgn]

Heres a booklet from the USCG for boat builders, its main discussion is on safe powering a boat. Some nice calculations!http://www.uscg.mil/d13/units/msopor...bp16761.3B.pdf

[ 09-02-2001: Message edited by: sturgn ]

[ 09-02-2001: Message edited by: sturgn ]

[urb]

Sound like you're looking for the least amount of power needed to push a hull. Here a some of the smaller boats I've played with.16 ft skiff 25 hp ob 22knts, 16 ft. skiff 40 hp ob 31 knts, 16 ft. skiff 50 hp ob 34 knts, 19 ft skiff 130 hp ob 44 knts, 20 ft w/windshield 125hp ob 40knts, 19 ft w/w 275 hp od 55knts, 22 ft w/house 225 ob 49 knts light boat 12 degree bottom, 21 ft w/h 260hp od 41knts heavy boat 20 degree bottom

[CAGEY]

Hi Floater, welcome to the board. Sturgn gave you some good info. They set those standards for your protection. Overpower a boat and she will go down stern first like a torpedoed ship. I once observed a 90 hp installed on a 12 foot wooden boat, When it was given full throttle it saluted with the bow and sank, all in about 6 seconds. Hope to see more posts from you. Cagey.

[Floater]

Thanks for the info. The boat came with the 80 horse and it moves along pretty good. But when I read threads that people have their kickers wide open just to stay in place, it makes me wonder. What are the conditions (# of people, boat size, kicker size)? I feel ok if I put in at the oyster house and troll the dolphins but I'm being cautios with bouy 12 or government island.

[boater]

i have a 21 foot aluminum boat and have a 10hp kicker and it works fine for me

[Tinman]

The rule of thumb I use is that 1 horsepower per 30 pounds of weight will get you 30 mph at full throttle. When calculating weight, include everything, hull, motor, fuel, passengers, ice, anchor,gear etc.

Example: Total weight is 1000 pounds. 1000 divided by 30 is 33 horsepower. So, a 30 horsepower motor should get you just under 30 mph at full throttle. That means you would cruise comfortably at about 24 mph, which would be fine.

I got this formula from a great book called The Powerboat Handbook, by Jim Martenhoff. Jim used to be the boating columnist for Salt Water Sportsman magaizine, but that was years ago. I suspect the book is out of print as well.

Good luck

[Doubletake]

Floater, nice to meet you. I have a 19' sled with 175 hp and run a 9.9 kicker with a high thrust prop.
Remeber you loose 30% power going from a prop to a pump. Don't under power the boat with the main motor, you will never forgive yourself. My kicker pushes my boat well in slack water and also holds its own in pretty fast current in the river. Hope this helps.

Good luck

Doubletake