[SummerIslander]

I've owned/own two 13 ft Whalers (70s/80s versions) with the same problem. Root cause is none of these small Whalers were designed for heavy four-stroke engines sitting on the very very back, they were designed for considerably lighter 2-strokes. The 2006 is a very different boat that my old ones, but sounds like the same problem.

The current boat we have has the 4-stroke 25-hp Merc. It is a dog to plane. IMO 25hp is not enough power for this boat, period, even with shortened pitch prop. I have to trim in aggressively to get it up, then trim out again once on plane.

The first one we had, we replaced the original 1981 2-stroke Johnson 35 with a Nissan 4-stroke 30 hp (same as Merc engines) . That worked well overall power-wise but still needed a 10-inch pitch prop to plane. But: the additional 5 hp power alone was not enough, it still carved a huge hole in the water and took a long time to plane with 2 people.

What is needed is to lift the heavy back end. For both boats, I bought and installed Smart Tabs (passive air spring trim tabs, fairly easy to install) and the tab retraction kit (essential for beaching and trailering). This is the real fix, it aggressively lifts the back end of the boat starting at low speeds. It's a good product, I also use them on a 17-ft 90hp runabout to improve the ride and planing. Install as close to the sides of the boat as you can go to keep the ride flat. You will need to experiment with the angle adjustment to get it right.

In addition, permanently relocate the battery (consider a smaller lighter one, there are options these days) and gas tanks as far forward as possible.

Summary: For 13-ft Whalers to perform well, you will need 30 hp AND Smart tabs to get them on plane in a reasonable amount of time. 25 hp is marginal, but try the Smart Tabs and weight redistribution first see if that is good enough before the more expensive motor trade-up.

Good luck!