Hi everyone

Our local Surtees dealer reckons they fly with a 70 on the back. 44kg out over the transom is quite a bit; the 4.7 and 485s were very sensitive to having too much weight over the back but maybe the 495 is better in that regard?

If you want to find out the power to weight:

 That is for a vehicle, on wheels with min resistance , unlike a displacement hull, pre going over the bow wave to plain, then once on the plain, high area friction with water.. not greased wheel bearings
 To Calc the latter requires Gerrs and/ or Wyman's formula for the displacement.. needing to know hull water liner length displacement hp at the low rpms available

 Then the extra hp to get over the bow wave at that rpms.
 
Then once over Crouches formula knowing the constant requirements of modern trailer able hull, the hp at that rpms and speed, and the total gross weight

A very rough estimate / ball park in the plain.. guestimate/ assumption, total gross weight say 950kg cruise speed 25 mph will require min of about 35 hp.. plus to be well powered another 10 to 15% ...40hp
 Drop another 44kg on and guesstimate 2hp the cruise would pick up around an extra 1 mph.

To take advantage of either engine have 1 prop for towing another for general use

5 hp at WoT will most likely relate to only .5 maybe 1 hp in lower mid range... that would most likely be off set at that rpm range by the extra weight.
 An extra 5 hp at WoT , will most likely off set the extra weight a little.

Rozboon wrote: Our local Surtees dealer reckons they fly with a 70 on the back. 44kg out over the transom is quite a bit; the 4.7 and 485s were very sensitive to having too much weight over the back but maybe the 495 is better in that regard? 1.6L will have way more torque so be better out of the hole for pulling skiers.

Joker wrote: Rozboon wrote: Our local Surtees dealer reckons they fly with a 70 on the back. 44kg out over the transom is quite a bit; the 4.7 and 485s were very sensitive to having too much weight over the back but maybe the 495 is better in that regard? 1.6L will have way more torque so be better out of the hole for pulling skiers. 4.7, 4.85 or 4.95 - they are all the same hull. The first 2 just a different way of measuring them. The last a stretched outboard pod. They will all have the same weight sensitivity.