Originally Posted by Greenhead1984
Im not having any issues, just trying to get more hp out of my suzuki. It's not hitting the rev limiter, I just tinkering trying to get some more power.
Check if there is a same 30 HP model, if so, replace your carb 25 HP jets and change for the 30 HP jets, remove the air restrictor if your 25 is currently using one located between the carb body and engine head, basically a plate with holes. (get a spare parts manual to check both head parts to see if both are the same head) Some brands needs to change the whole reed valve assembly & carburator because the gas passages are thiner/wider comparing both models, a change of just jets will not update the next engine model.
Lost 6 months experimenting to change a Evinrude 10 to 15 HP, both same 250 cc head, changing a 15 jet didn't better the performance, was worst. Finally knew that you needed to change complete 15 reed valve assembly (larger intakes) + complete 15 carb and the cost was near $ 200. Sometines is better and cheaper to buy a larger standard model instead of converting after purchase. Examples 4 to 5 / 10 to15 / 25 to 30 etc.
This modification will work fine as long as both engines 25 & 30 have the same cubic centimeters, example 450 cc for both, the difference is that 25 is fuel and air restricted compared to 30. Maybe will need to change the pitch propeller, make a wot rpm run to match the best wot maximum rev engines for that model, example 5500-6000. If the change is possible to gain the extra 5 HP, move your linkage back to the position factory adjusted.