bv-falcon
23.04.2021 19:15:32
Re: Johnson 70hp - How fast does it push your boat?
See full version: Johnson 70hp - How fast does it push your boat
Re: Johnson 70hp - How fast does it push your boat?
Re: Johnson 70hp - How fast does it push your boat?
Right now, the boat does not lose more than 3-5 mph when fully loaded.
2017 Harris Sunliner 200
Tri-toon P+ Package
2017 Mercury 150 4 stroke more
I have an 18 ft. with a 60. I can get up to 23 mph (GPS) with wife and I and about 19, with about 8 people. You'll probably not be able to ski, but I can easily pull a tube with 2 people on it. Depending on where you are going to take the boat, with 2 small children, that should be plenty. You never know what can pop up in a lake (trees, stumps etc.) and going to fast can be dangerous.
#7 Post by NonHyphenAmerican » Fri Apr 07, 2017 10:43 pm more
So for 2' shorter it should be fine. more
Powered by Mercruiser 3.7 liter, 185 HP; Top Speed: 43 mph; Cruising: 22 mph. 3.2 miles/gallon. Hull: $1700. Robert & Eric Vader, Capistrano Bch, CA.
TNT October 29, 1998: I just wanted to take a quick moment to express my pleasure in the plans and framing kit I recently purchased for the TNT. I found the instructions and plans to be complete and easy to follow. I worked on it in the evenings and some weekends and completed it in under two months, which was much faster than I had figured it would take. . I currently am running a 25 hp with a 10 x 17 prop and she moves and handles great. Tony Allen [links]
Last year (May 1998) we, C. Hogervorst & JP Wolf from Holland, completed our building of the "Kingfisher". We finished the project in one year. The boat is powered by 80 hp, and makes a speed 30 knots.
Roustabout: I built mine in 75, powered with a Mustang 289-Ford V-8 and Volvo I/O. She's a little rear end heavy but OK. Roustabout is NOT a rough water, or off shore boat at all! After 23 years of service, only the epoxy paint coat is worst for wear! I've had her up to 51 mph, by myself, in smooth water. Mike Stabler here
TNT 5-1-01: . The boat has a 20 hp. Mercury engine which pushes it along pretty well, and a rotary steering system which was quite simple to install. Although it took over 325 hours to build, the results are worth it. Kyle Crawford [links]
Thu, 10 Aug 2000
TNT: The length was increased 4 inches in the back behind the divers seat. The hull was professionally fiberglassed and gel coated. Seven coats of varnish so far on the deck; 2 go-kart seat side by side, all Mercury components: Tach, Speedo and control box.
. Fiberglassing the hull is highly recommended in my book. It added about 60 lbs. but the weight is low and it is indestructible now. The motor is a 25 Merc Stock electric start with a 18 inch Mercury Racing copper which so far after two weekends has pushed the boat to 42 mile per hour. Mike Moore.
(Note: Normally fiberglassing would add 10 to 15 lbs.) [links]
A motor larger than a 40 becomes dangerous for several reasons. First it is too heavy for a 13 foot boat. On a classic pre 1972 boat the transom would almost be under water at idle. Second, it will make the boat go too fast. 13 foot boats do not need to be going 50 miles per hour. A dive into a wave can easily throw everyone off the boat. Also, a quick turn can flip the boat. Going fast in a boat is fine but it needs to be done in a longer more stable boat. For the 13 foot classic Boston Whaler stick with a 40 horse or below. [links]
As you go up from a 20 horsepower you will no doubt want to switch from a tiller steer motor to a steering wheel. As a general rule of thumb you get about a mile per hour from each horsepower. A 20 hp will do 20, a 25 will do 25, a 35 will do 35 mph and so on.
Lets first start with the absolute minimum engine needed to plane the boat. This is going to vary between a 9.9 horsepower and a 15 horsepower motor. A lightweight Whaler with a lightweight person aboard can possible achieve a plane with a 9.9 horse motor. And as stated above, a hydro foil will help. If the boat has more than one person aboard or is heavier because of water intrusion then this will not be enough horsepower. [links]
A 20 horsepower motor is the minimum that you will need if you want to carry several people at one time and want to pull wake boards or kids on water skis. It will get onto a plane very easily and travel about 20 – 25 miles per hour. Gas mileage will still be great and trolling still nice and slow. We have a 20 horsepower Tohatsu with electric start and tilt on ours. It is great for the kids because it does not go too fast but its still fun and feels like your flying even though you are only going about 20. [links]
A 40 horsepower motor is the largest that I would recommend for the boat. It will carry you along at about 40 miles per hour and will put almost any size skier. You would need to be careful traveling at high speeds in rough water. A motor this size is not recommended for kids or beginners. Keep them in slower boats for their own safety. here
A 15 horsepower outboard will more easily achieve a plane even with more than one person in the boat. The top speed will be around 15 – 17 miles per hour. If you intend on pulling a wake board or skier you will probably be disappointed in performance. For a single person who uses the boat for fishing a 15 is going to be sufficient. Your gas mileage will be great and you will be able to troll at slow speeds very well as well as get up on a plane and get home on time.