Skip,
Thanks for the interest and info..Mainly I will be using my boat with family and occasionaly some friends..I will be visiting both agents of Suzuki and Yamaha and get more info. Meanwhile one last question in your opinion a 115HP will be enough for an 18ft boat weighing 680kg?
Thanks again much appreciated
Depends on the boat and it's hull design. Deep V hulls with a high deadrise will require more power than shallower Vs but then ride better in rough weather.
What boat is this engine going on?
115hp is usually ideal, I had an 18ft with a 90hp that was rated for max 115hp and I always regretted not going for the 115.
Some 18 foot boats will take up to 150hp depending on design and rating. I always advise that people put the largest engine the CE plate is rated for. It's always better to run an engine at lower revs than having to push an engine at higher revs on a boat that is slightly underpowered.