Initial takeoff issues

[Eodbru]

Could a bad carbon seal cause the ski to not hookup on take off? My 2005 RXT struggles on take off, I give it throttle and it just revs like the pump is not creating any thrust or actually turning. If I feather it at low rpms I can gather some speed and get up on plane eventually. I have noticed a loss of 5-10 mph on top end (stock speedo so actual mph likely less!)

Is this a wear ring/impeller clearance issue, if so how big of a gap would cause this issue?

 

[Joseph9936]

Had the same issues. Had to replace carbon ring and new wear ring. My second one I had to replace carbon ring, wear ring and then line up the motor to pump

 

[Coastiejoe]

Wear ring and or CS are the normal causes.

 

[AircraftDoc]

Bad cavitation is cause by bent impeller. A worn wear ring will give you loss in acceleration and top speed. But not what you are describing. I had a real bad take off out of the hole. Flashlight and mirror reveled a bent and flattened impeller. I removed the impeller and ground down the leading edge with a grinder. Regreased and installed per MM. Problem solved.

 

[Eodbru]

So having water in the ski with the previously described problem, CS failure?

 

[3ftDeep]

Most likely. It can be a combination of the carbon ring, and the rubber bellow losing its spring (which is also critical in making a good seal). When you replace the carbon ring you also replace the bellow, so you address two issues at once.

 

[Sportster-2001-951C-Stock]

If the ski is run on the trailer, there's no water cooling to keep the heat generated by the carbon ring seal from softening the rubber bellows. The rubber bellows acts like a spring to keep the carbon ring pressed flat against the rotating stainless ring, so once bellows tension is lost it's more prone to air/water leakage. Age alone, will reduce tension as well.

Sometimes the carbon ring can be cracked or worn out on the inside diameter, egg-shaped and will become off center enough to allow an gap where air/water can leak.

If the carbon seal is leaking, water enters the bilge and/or air from the bilge is sucked into the impeller, leading to airation of the impeller and loss of thrust. (not to be confused with on purpose, but similar result as cavitation).

Cavitation is more prone if the impeller/wear ring are damaged.

Any/all of the above might be the culprit in your case, careful inspection of wear ring and impeller should help isolate the real culprit.