The Sisu boats were built in the 1970s and 80s by Sisu Boat Inc. of Portsmouth, NH. The hull designs were created by Royal Lowell. 22, 26, and 30 foot models were offered. They were very popular, and many are still on the water today.
The term "sisu" refers to a common Finnish concept of "stoic toughness" or perseverance. The literal translation is "having guts" - basically, the spirit of will that survives and enjoys the harsh winters of Scandinavia. 'The Power of a Finn is the Sisu Within'
Sisu closed its doors in 1988, and the hulls migrated to various builders. The Lowell Brothers are now proud to once again offer the Sisu 22 and Sisu 26, as our Lowell 22 and 26.
Most of the companies that provided components for Sisu boats have since gone out of business. We use Hamilton Marine as a great source for boat components.
The Sisu windows were originally made of plexiglass, which has a tendancy to get cloudy. Replacement can be tricky because the windows often have a 2" corner radius, whereas 3" is now the industry standard.
Here are companies that we know of who offer windows that will fit for Sisu replacements. (We don't recommend plastic windows.)
When ordering new windows, do a perimeter measurement and two diagonal measurements. (See the bottom of this page for an example: http://www.bomon.com/EN_calculate.html)
We have had good results with full-length spray rails for the Sisu round chine boats - this gives extra stability at higher speeds, while maintaining the smooth ride.
SIsu 26 - Repower
It is important to keep the engine weight less than 1000 lbs, for best boat performance.
SISU 26 Repower - Outboard
We find the outboard to be more efficient. We recommend 250-300 hp engines. A 250 hp will probably give a speed of about 31-33 kts. We like the E-Tec or Yamaha engines, 2-stroke.
SISU 26 Repower - Inboard
We recommend 240-300 hp or more. Engines that we like include:
SISU 22 - Repower
SISU 22 Repower - Outboard
We would recommend a 90-150 hp or more engine, depending on how heavy the boat is.
With a cabin, 135-150 would work well - minimum 115.
We like the Evinrude E-Tec engines.
SISU 22 Repower - Inboard
For a diesel, we recommend a smaller Yanmar or a Steyr, in the 4-cylinder range.
140-180 hp, up to 240 if you really want to go!
There aren't many small gas engines that we know of - perhaps a GM Crusader (V8).
However, this would require some modification to the deck/engine box. Small inline engines are pretty much all diesel now, and we are not aware of any gas ones.