Conversion to 50 HP

After studying the parts listing I noticed that Selva Madeira 40 XS is identical to Selva Madeira 50. The only difference is the part number 73 labeled as an exhaust separator. Once again visiting Gommonauti.it forums I was convinced that removing that plate should give more horsepower for my Madeira 40 XS. It seems that the only purpose of that plate is to restrict the flow of exhaust gases.

I proceeded by removing the lower unit as described in the previous post. For my surprise there wasn't any plate, I guess the previous owner has removed the plate already. My engine was manufactured in 2005 and it should come with the plate. I cannot say for sure but it looks like you can remove the plate without disconnecting the shift rod, this makes conversion quite easy. You may need to adjust the mix and idle screws after the conversion. 

Exhaust downwards

Exhaust upwards

So how much more power can you get from this conversion ?

I cannot provide any real data since my motor was already altered, I can only speculate. Selva manual states that on average Selva Madeira 40 consumes 14 l/h WOT and 50 HP model 16 l/h. The provided average consumption for Selva Madeira 40 XS is 15 liters per hour, could this mean that out of stock 40 XS has actually closer to 45 HP and you would get only 5 HP more from this conversion. I also would like to know what does XS mean, is it Extra Strong or something else ?

Anyway, remember that if the motor revs above 5500 rpm after the conversion you need to consider higher pitched propeller, at least Solas Amita 3 (Yamaha) propellers are available in 11-17" pitch range.