New Yamaha 4 stroke 70hp

[Cuadra]

I have a Zodiac Futura Mark III that weight 260lbs with a Honda four stroke 50 hp that weight 97kgs

I want more speed out of my boat so I am changing engine for a New Yamaha four stroke 70 that weight 118 kgs.

I want this boat to be very fast.

I'm thinking on a 17 o 19 Pitch prop of maybe 21.

Boat is light and I'm usually alone.

Somebody recommend prop pitch and diameter for best top speeds at WOT 6200?????

What top speed can I obtain.

 

[deejaycee_2000]

Re: New Yamaha 4 stroke 70hp

Welcome to boats ...... 19 pitch merc racing cleaver should pull nicely ..... I'm not sure what speed you will get from a 4 stroke, but with my 70CES yam 2 stroke I get 139 km/h on gps ...

 

[SIBRider]

Re: New Yamaha 4 stroke 70hp

How fast do you want to go? Your boat is rated to 37 mph. 50 hp should be plenty to go that fast with right motor height and prop pitch.

 

[Sea Rider]

Re: New Yamaha 4 stroke 70hp

To obtain 50 or 70 HP full power the engine can deliver, need to have proper leg height and trim well dialed to start with, install an induction tach if engine doesn't count with one. Go for a wot spin with you alone and check max achieved rpm, compare them with max wot factory stated parameters. Will know if under or over proped. Assume you have a center console, right ?

To select a different factory delivered prop need a tach, if not, it's a expensive wild guess playing with pitches that can ruin your engine in a short term by lugging or over revving which currently you don't know yet...

Happy Boating