What pitch prop for Tohatsu/Evinrude 9.8

[Whaler 73]

I have a 13 ft Classic Whaler that I just put a Evinrude 4 stroke 9.8 but the motor has a high thrust 8.7 x 7 which only yields 6 mph GPS. Boat weight approx 320 lb, people weight approx. 200 lb, motor weight 120 lb. Can I go to an 8.5 x 9 pitch?

 

[Sea Rider]

Welcome to Iboats,

Can go with whichever prop you want, but that's a very bad idea. Need to tach with an induction tach current OB as loaded and check max wot revs factory stated on calm, flat water cond provided that load is evenly distributed on deck, OB well trimmed and transom seated at the sweet height spot for best prop thrust.

Will know which less pitch to go for OB to rev best at its full wot revs. Don't know it possible to plane such boat with a under powered OB, assume just fast displacement speed with OB running strong and safely inside its max wot rpm range.

With how many boaters will usually be boating with ?

Happy Boating

 

[Faztbullet]

That hulls rated for a 40Hp if I remember right and a 10 hp motor aint going to get you nowhere fast no matter the pitch.Hull has a factory hook in it....

 

[WesNewell]

assuming you weights are correct. mercury prop selector for for a 4s 9.9hp 2.08gr engine recommends a 12p prop for an aluminum tiller boat weighing 320# and a top speed of 26 mph @5500 rpm.

• Boat type: Aluminum - Tiller
• Usage: Overall good performance/0 ft
• Engine Manufacturer:
  Mercury
• Engine Type: Outboard
• Engine Year: 2017
• Number of Engines: One
• Engine Family: FourStroke
• Engine: 9.9 2cyl (209cc)
• Drive / Gear Case: 8-9.9 HP 2 cyl, 2.08 Ratio

[h=3]Details[/h]

• Calculated Pitch: 12.08
• Calculated Weight with engine(s): 688.20 lbs
• Calculated Engine RPM: 5,500
• Calculated Boat Speed: 26.00 mph

 

[WesNewell]

looking up specs on the whaler, the boat weighs 640#, not 320, so calculated best pitch is 10.43P, so I'd go with a 10P prop and expect ~20mph.

 

[Whaler 73]

The new whaler 130 weighs 640#, but the Classic Sport only weighed 320#. Newer whalers have way more fiberglass.

 

[Whaler 73]

Thanks for all the current input. The lakes and reservoirs I fish in have a 10 hp max limit. Maybe some previous Whaler owners have more experience than I have . I have read people with 6000# sailboats can get 6 mph with this motor.

 

[WesNewell]

The new whaler 130 weighs 640#, but the Classic Sport only weighed 320#. Newer whalers have way more fiberglass.

If that's the case, then you should probably go with a 12p prop.