[Fr. Frank]

As a SeaCraft dealer in the early 80's, I rigged a lot of 20' SF hulls with either an 85 hp or 115 hp V4 motor. The 115 was the most common power choice. However, the 115 had a 10% top speed advantage of about 3-4 mph over the 85, and used about 10% more fuel across the spectrum. Most people think that because a 115 is laboring less at a cruise of 25 mph, and therefore should use less fuel. We never found that to be the case.

According to Carl Moesly, the "design motor" for the 20' SeaCraft hull was a single 110 hp Mercury "Tower of Power" inline 6 cylinder motor, which actually produced between 88 and 90 hp at the prop shaft on average. A pre-1976 Mercury or Evinrude 135 hp motor averaged 114-115 hp at the propshaft.

With the exception of Tohatsu/Nissan, all current production 2-stroke 90 hp rated motors produce an average of 103-105 hp at the propshaft. The Tohatsu/Nissan averages 81 kw or 108 hp. However, service on T/N motors can be hard to find.

Even though they weigh the same 375 lbs, and had a cost difference of only $350, I elected to go with a 90 hp Optimax over a 115, largely because of my experience with rigging these hulls with 85 hp and 115 hp motors 25 years ago. I knew the 90 hp was adequate to the task. I am quite satisfied with that choice. (especially the 5+ mpg at cruise)