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In smooth water the difference is 1-2 mph tops. The speed difference widens as is gets rough, that is why racers use steeper props. A 9-15 will feel slower because it accelerates stronger at low speeds.

At least get a big hub swirl, its worth about 40% of the total gain. A larger diameter pump/inlet can make more thrust at very low hull speeds. This is why big pumps with big engines are so impressive. The advantage diminishes as speed increases. If you blip the throttle a lot then lowering the...

A standard SBN has a throttle shaft and venturi where a MX carb does not. An SBN 44 has only 39mm of airflow area where a bike carb is almost unobstructed. A bike can be lugged down at full throttle so their carbs cant be too large or else they will not draw fuel. Watercraft dont have this...

Aluminum has very low fatigue life compared to steel. FPP used thin aluminum on SJ chambers because it hangs off the coupler. The side effect is cracking over time.

The pull up carb is from an X2. I have used a stock X2 flame arrestor with the cable mounted on top. Best to sell the X2 carb and find a standup model.

Dont tune with expectations of what is should be. You have found the limit of your fuel more than once. Just back off the timing and compression. Then spend more time with break in and carb tune.

A lowered cylinder will gain considerable response at the expense of power. It requires a good pump in order to gain thrust at low speeds.

All large MFGs own the sports organizations that they provide equipment for. They make sure the rules protect their products. They will not get into anything that they cannot control. As a group we are getting older, better financed, and have learned enough to operate on a component level. This...

I can see detonation erosion on the aft piston. It is possible that air in the line pushed an otherwise sound setup over the edge. Lowering the compression and timing will increase your margin of error. Also open the top screw more on the aft carb since it feeds the hot cylinder.

You need the whole SJ inlet in order to get good low speed thrust.

Your engine is set for higher octane than you are using. The two biggest factors are compression and timing, back off both of those and this problem will disappear. Carb tune also contributes greatly, the top screws should be set a little rich of peak power for maximum reliability. Running the...

The bottom screw is for idle only, set it on the trailer. Pilots are 1/4 throttle. Main jet and top screw control full throttle fuel flow. Raise the pilots to 120, tune the top screw for hardest acceleration. I expect the top screw to end up less than 1 turn out with 140 mains. I would use an...

Try an Adel clamp.

People are still breaking mounts, even good ones. They just dont cry about it anymore.

A short light weight hull is mandatory for flat water flips, even with a big engine.

What exactly are you wanting to do on your ski?

This was a case where the operator was more important than the tool. My bearings had a large edge radius, otherwise I would have undercut the inside corner while it was on the lathe. Next time I will cut the shaft for a 5205 bearing.

I sanded my last Solas with some 600-1000 and oil. I spun it in a lathe and then pressed a bearing in and out until I had the fit loosened up a bit. It took three tries before I was happy. Dont do this unless you are willing to check and recheck the fit carefully because you must get all the way...

A large hub impeller is worth nearly half of the total gain. It wont offer greater maximum thrust, they just dont lose as much as the water gets rough.

That would be a good trick considering there is no up front specifications for the builder to meet.