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A 650 or AM 84mm nozzle will make the most improvement in low speed thrust. The pump is too small and the hull is too heavy to get much pull out of the hole.

Or you have an exhaust leak! BTW make sure to use a 61x gasket or add holes to a 62T to match the head if you have not already.

I had a tiny exhaust leak cause the same problem on a couple of skis. Prop up the rear of the hood an inch or so and tape it in place. If it runs fine you will know the problem.

Everyone keep doing the same thing over and over trying to copy a blaster. They always end up with something that is more like a blaster and less like the freestyle ski that everyone wants. Hull builders, try modifying your skis into great fixed steers. Forget the seat, its just in the way...

All that afterfire probably blew up the stock box.

The original Techiplate is PAG oil, it mixes with alcohol, nitro, and gasoline. It will also absorb a lot of water so it is mainly used with alcohol. Super Techniplate is the same but with some castor to extend its max temp. All their other formulas are gasoline only and ester based. These...

With a single inlet line, water flow between cylinders are controlled by the small holes in the exhaust manifold gaskets. It is common for gravel to block the lower passages at the exhaust manifold gasket. This will make one cyl cooler than the other. Its best to increase the size of all...

The Solas "S" is a little lighter load than a stock blaster prop. You can improve the low speed pull by raising the trailing edge 1/8" or more as needed. The big hubs prime faster which makes a significant difference in rough water.

The yamaha 701 is easy on its oil requirement. Use TCW3, it has better corrosion protection. You can spend $50/gal on "racing" oil and end up with more wear due to rust over time.

You will need to custom cut the domes.

Does the engine sound clean when you are cruising around or does it sputter? Should be fourcycling a little at 1/4 throttle. Increasing the pump load makes the carb settings leaner.

The stock 650 nozzle is big enough, the only way to go larger is with a now hard to find aftermarket nozzle. A straight 15 will pull harder than 15.5 or 16, these maintain speed better in races. A modified low pitched big hub 750-800 impeller is best. A 750ss/xi shaft can be used for customizing...

The bottom screw is most effective at idle . The pilot/popoff is in play as soon as you crack the throttle. Overly rich mixtures will need more spark lead. This combination is what provides the good throttle response that we like. A clean pilot/popoff with 35 degrees will often be detonating. I...

Use a longer inlet for high speeds. Go as wide as you can up to the bulkhead for flat water freestyle. Japanese hulls take this concept to the extreme.

It's easy to soften these engines into good easy to ride power plants. You just won't have the response and pull that it had when it was tuned for max performance. Can't have everything. Just turn down compression/timing, lower the exhaust port, and increase pump load. It turns into spending a...

Any fuel line pressure has the effect of lowering popoff. This will change your idle and pilot mixture a lot. He was able to set the idle mixture with line pressure alone. This is why using published carb specs is often foolish. The only advantage of low line pressure is so an air bubble won't...

The old 14/17 is too much load for good low speed response plus it won't prime as fast as large hub impellers. A Hooker 9/ 15 will perform much better below 30mph.

Short freestyle skis spend most of the time at part throttle and below the pipes resonant rpm. This area has very cold combustion temps. B-ES plugs never get up to temp in this apication. Plugs with protruded electrodes will stay cleaner. The old standard plug is fine as long as you are not...

They have been making the header smaller than the port anytime a tuned pipe is intended. Yamaha 701 had larger headers than ports because it was not designed for a tuned exhaust.

Too much pump load will do the same thing.