"What modifications can I make to improve the performance of my 1987 Kawasaki 550, considering it is almost completely stock except for an intake grate and ride plate? Would it be risky to modify the engine of an older ski like this? I am looking to increase acceleration and top speed and have a budget of around $500. Can you suggest any modifications that would give me the best value for my money?"
Absolutely, your 1987 Kawasaki 550 is a great candidate for some modifications to boost its performance. The fact that it already has an intake grate and ride plate installed is a good start.
To get more acceleration and a higher top speed, you can start with a cylinder head modification to increase compression, which costs only $80. You can also add a water bypass in the waterline between the head and pipe for an additional $25 to further enhance the engine's power.
For a significant increase in acceleration and speed, you can replace the stock aluminum prop with a Solas Impeller 15-inch stainless steel that costs $215. You can also consider boring the fixed exit nozzle on the pump, which adds to the thrust for only $48. Installing an aftermarket flame arrestor, along with a 2.0 needle and seat in the carb, will provide even more power gains if you're willing to spend a bit more.
Another great modification is to move the exhaust exit back about two feet on the hull to let the exhaust gases out just behind the battery. This is a relatively easy mod that significantly reduces the exhaust gases that the rider gets exposed to, and you'll be wondering why you didn't do it sooner.
Overall, these modifications will significantly improve your Kawasaki 550's acceleration while keeping the RPMs down, which is crucial for increasing the engine's life, especially the crankshaft bearing life. You can achieve all this while sticking to your $500 budget and getting real returns for your investment.
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