what size outboard should I use for auxillary power

[Wjdunham]

I recently purchased a used 25C that did not have a kicker outboard for auxiliary power. I'll be using our boat in Southcentral Alaska where help my not be readily available should I lose power. Is there an minimum sized outboard to purchase that will be a good auxiliary power for a 25C? I've been looking at the posts on this site and have seen 5hp to 9.9hp by different 25C owners. I am not looking to troll with this motor, only to have available should the main engine stop function in open water.

 

[Zundels]

Out of Kodiak harbor we used a 9.9 two cycle outboard to troll and as back up power. Mounted the outboard to a bracket we bolted on the swim step. Found the 9.9 would move our 2009 R-25 at about 3-4 knots which was enough to get home or against moving tides. The 9.9 would also troll slow enough to get the right action on the salmon lures.

Reasons for using the two stroke 9.9 include weight, for mounting and un mounting the outboard. Had to move the outboard to the dingy now and then so it needed to be light enough to move over the water. Used the dingy to access and clean the gill nets or motor to a beach. When mounting or moving the 9.9 would also tie a line from the kicker to the boat so if dropped we could pull out of the water. (never was needed)

Was a bit cumbersome how we steered the kicker. Had to lean over the stern to steer the throttle handle at an angle and did not have it wired into the boat steering.

Don

 

[R Baker]

Years ago on sailboats a rule of thumb was 2-4 hp per ton of displacement. I had a 26 ft, 3 ton boat with a 6.6 hp diesel; and a 32 ft, 5 ton boat with a 12 hp diesel. Both of these examples are in the 2-2.5 hp per ton range, and could easily travel at their hull speed (square root of the waterline length X 1.33). Given that power boat hulls are not as slippery as sailboats; I would consider the higher end of the ratio . The engine should be fitted with a displacement pitch prop which are generally available for small outboards.

 

[Wjdunham]

thanks for the comments! they were helpful.