1996 Sportster with very little acceleration

[buckhammer]

Hello everyone,

I run a marina in MT and i had a guy bring in a 1996 Sportster today. It is running fine and the engine achieves high RPM, but the jet and thrust doesn't really respond to the added power from the engine (some, but not nearly enough). It idles and putts around OK, but there is not a big push available.

The jet is clear, intake is clear. Shaft is clear. Wear ring looks to be in mint condition. The boat only has 17 hrs on it. This guy bought it a couple of months ago and the history isn't entirely clear. The impeller is spinning without obstruction; just not fast enough?

Any ideas would be appreciated. This fellow would love to use his new boat. I will see him again tomorrow at 4 PM.

Thanks Guys!

 

[Dr Honda]

You have a massive air leak. It could be coming around the ride shoe... But I'm going to bet it's the carbon seal on the driveshaft. The one in my boat looked OK, but the first time out... it would hardly move. Changed the seal, and it's supporting parts... and now it goes as soon as I mash the throttle.

 

[buckhammer]

I am not a mechanic, but pretty handy

Is this type of repair beyond a regular wrench monkey's grasp? I will figure out where the ride shoe and carbon seal are located and investigate. Any other pointers on finding/diagnosing a leak in one or the other?

Thanks soooo much!

 

[seadooya]

unless you pulled the pump to take a gander at the wear ring, you cant tell. Pull the pump, most of its damage is behind the impellor, if not the impellor itself.

 

[buckhammer]

You can't see the wear ring?

I crawled underneath and the entire intake/impeller/ output assembly deal looks brand new.

Also, this boat only has 17 hrs on it. No signs of damage or debris though impeller. Do you think the air leak is more likely?

Thx for the input.

 

[Dr Honda]

The ride shoe is the part of the pump that is glued to the hull, and the pump bolts onto it. They are known to have a very thin coat of sealant from the factory, and they can draw air around the sides.


The carbon seal is in the engine compartment. Remove the gray plastic cover behind the engine, and you will see it.


Although, SeaDooya is right about the wear ring... I've found they can be pretty rough, and only cause minor cavatation issues. Thats why I think it's the carbon seal.


If this boat truly has 17 hr on it... I bet you will find the stainless ring has slid back, and is touching the rubber boot on the PTO.

The Carbon seal works by putting pressure on the stainless ring. The original thing that held the stainless ring in place, was a rubber O-ring. They are known to crack, and fall off. When that happens, the pressure is relived, and it sucks air.

If you find that as the problem... you may get away will just sliding the ring rearward, and replacing the (now gone) O-ring with the heavier metal C-clip. (the new factory upgrade replacement)


It's not hard to change... but you will want to get a shop manual so you know what all the parts are.

 

[seadooya]

it being a 96 sportster, go to dealership, get/order a new neoprene seal, cuz you'll need it, when removing the pump, and like Honda said, remove the grey shield from the motor, and look/inspect the carbon ring and the position of the steal collar, the "carbon" rides against.