Repower Question

How fast could a 50-70 hp motor push a flats boat weighing around 900 pounds? Weighing some options.

Blue


Proline 201WA
Aloha 24ft pontoon (LooneyToon)
Old Town stern with 7.5 johnson

I’m afraid i don’t understand (new to the idea of repowering a boat, don’t have much mechanical understanding). Could you elaborate?

“Only a fool thinks he knows it all.”

Blue means there is no way to know. 50-70hp is a significant power range. Flats boats come in many different shapes/weights/etc. What prop? etc. etc.

Here’s an example one power / hull combination.

A Bentz-Craft 16’ one piece hull (650 lb hull) with a new Yamaha F70 will creep up on 50mph running as light as possible and with the exact right prop. But, a Bentz is designed to get up on top and make speed - has a decent pad and shaped to catch air under the bow adding lift. Other similar hulls won’t have a pad and will be a little slower. Some hulls, much slower.
That same hull with a 50 will run in the low 30s.
Add some weight and everything slows down.

To get any kind of reasonable answer you’d have to know what hull and what motor.


17’ Henry O Hornet w/ Johnson 88 spl
26’ Palmer Scott project hull
14’ Bentz-Craft w/ Yamaha 25

Thanks for the clarification. I’m considering a project boat which is a 2001 18 ft action craft flatsmaster (950-1000 lbs) and putting on a Suzuki DF70 or Yamaha F70. If I don’t mind my top speed being around 30 mph, can I put a motor on this boat in the 50-70 hp range?

“Only a fool thinks he knows it all.”

70hp is going to small for that boat. whats on it now? didnt those come with a 115hp?


Proline 201WA
Aloha 24ft pontoon (LooneyToon)
Old Town stern with 7.5 johnson

Evinrude 115 2-stroke is currently on it, but the owner already stated it needs a lot of work. I was thinking about putting a four-stroke on it and was trying to get a ballpark cost estimate to see if the project was worth taking on.

“Only a fool thinks he knows it all.”

Agree with TheMech. 70 is going to be pretty weak for that hull. A 90 might work. 'Might.
Can you find the recommended power range from Action Craft. I’d give them a call and see what they said.


17’ Henry O Hornet w/ Johnson 88 spl
26’ Palmer Scott project hull
14’ Bentz-Craft w/ Yamaha 25

Do like Palmer said and call AC. I don’t know that exact hull but similar shape and weight are running 115 to 150 range, I don’t think a 70 or 90 would cut the mustard and would kill resale if you ever wanted to part with the rig.

lots of those were rigged with a 130 hp Yamaha 2 stroke- it’s what is on my 18’ Scout flats boat- or a 135 hp Merc, very good power match up.

I have a 17 actioncraft coastline with a 90 yam 4 stroke. I get only 38-40 mph top end loaded. Boat is an 89. Floats in 4"

Tall Sail Marine

17’ War Eagle approx. 900# Yam F70 lower-mid 30’s with 16P SS prop

an 18 actin craft with a 70 is going to struggle to see 30mph, but its gonna be very close.
you are going to kill that little motor on a boat like that, as its gonna have to run WOT all the time

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