My buddy and I each have Spark 2up 90hp's that were using for testing. We're also doing our testing on a lake this is pretty calm and about .75 miles in length. This spring I started doing some mods to mine and we have raced side by side after various points of modding and I thought I would share my results. First off we have identical Sparks but I'm 6'2" and 245lbs, my buddy is about 5'11" and 170lbs. Each time we raced side by side we each rode each machine twice to get an accurate idea of the difference that the mods made and to try and take rider weight out of the equation the best we could.
First mod was SS wear ring and Solas prop. This made a slight difference out of the hole but not too significant. With the heavier rider on the Spark with the mods we were about neck and neck and with the lighter rider on the Spark with the mods it jumped out to about a 2 ski length lead and held it up to top end. Didn't seem to change top speed at all but it did make the speedo read slower since it changed the rpm's at a given speed and the speedo's run of the rpm's.
Next step was adding R&D air intake, R&D free flow exhaust, R&D aqauvein intake grate, R&D pump seal kit and R&D ride plate. With these mods the Spark hooked up much better out of the hole and stayed hooked up all the way to top speed, top speed was about .5-1 mph faster than stock with either rider. With the heavier rider the modded Spark jumped out about 1 ski length out of the hole, then the stock Spark caught up in the mid-range and then the modded Spark slowly pulled ahead with the slightly higher top end. With the lighter rider on the modded Spark it jumped out to a quick 3-4 ski length lead and continued to gain a lead of about 5-6 ski lengths buy the time they hit top speed. I will note that these mods are known to make a much bigger difference in rough water. We'll be doing a day trip in the ocean within in the next week or so and will do some more testing there.
The last thing we're going to do is a V-tech tune. I know everyone says to do this mod first but we wanted to gauge the performance gains of the other cheaper mods first since not everyone can afford or wants to do the v-tech tune.
I know there is a lot of people out there with far more knowledge than I have when it comes to jet ski's or the Sparks, if anyone else wants to chime in on these mods or has any questions please feel free to ask.