xl 800 wont plane off

[shadowman]

Hey guys,

First post here so I thaught I would say hello first. I was a Marine technician for years and always worked on my own skis and motors without problems. I still help a local dealer sometimes through the summer when his workload is high. That is how I stumbled across this monster. Please read this and give me any advise you can. Thanks in advance.


Premiuim engine installed last year engine was broken in and set through the winter. When the ski was started this spring it would only run about 13 mph, and would run smoothly from idle up to 13. I first thaught the carbs must be gummed up, Nope. I then noticed the servo motor was not operating the PV's. This is when out of frustration I sent the ski out to the dealership to get it sorted out.

The ski was at the dealership for a few weeks and they tried everything that yamaha could recomend and the ski still runs the same. They replaced all sorts of electrical items and could not make the ski run.

So now its back in my lap for round two so I thaught I would check the PV's for proper operation, That checks out. So I decided with the exhaust loose I may as well check for blockage there, That is exactly how it acted anyway. I found the muffler full of water, when I blew air threw the exhaust from the engine I could feel pressure build up and then it would bubble On through and exit the hull. Is this normal? I could understand some water in the exhaust but this seems like a blockage.

Any advice or comments would be appreciated.

[boudin]

Re: xl 800 wont plane off

You didn't say what year ski, but have you checked the catalytic converter? Sounds like it may have broken up and is clogging the exhaust.

[Madfish]

Re: xl 800 wont plane off

If your XL800 is not getting up on plane, but engine is revving, you may have a pump issue. These skis have a common problem with a pump seal on the bottom of the ski. The seal is about 8 inches long and 1 1/2 inches wide and fits between the pump assembly and the hull. If this seal gets blown out or gets loose, you'll get cavitation.

The other problem you may have is a very common problem for everyone using pump gas with ethanol. If your ski has sat for more than 60 days without a marine ethanol treatment added to the gas, you probably have condensation and/or water in your gas tank and this will make your ski act like it does now. To correct this, remove all gas from tank and lines and carbs, and replace with fresh fuel.

[shadowman]

Re: xl 800 wont plane off

Thanks for the quick reply Boudin,

Sorry about leaving out the year, it's a 2001. All I have done so far to check the exhaust for restrictions is to put a peice of plexiglass on the large exhaust coupling and blow air in through a drilled hole. You can feel it build up some pressure then it will sort of gurgle and you can hear air bubling through the large aluminum chamber in the rear compartment of the ski. Is it normal for this chamber to be full of water? Is this the converter you speak about?

[shadowman]

Re: xl 800 wont plane off

Madfish,

The ski isn't cavitating, If I slowly add throttle from an idle speed it will accelerate normally untill it reaches a certain rpm then any more throttle input does nothing. As I open the throttle further there is no change in the engine, no bogg, no revving, it just continues to run smoothly at around 13 mph. I first thought the choke plates were partially closed but that wasn't the case. Im probably going to flush the entire fuel system anyhow and rebuild the carbs as well.

Thanks for the input.

[boudin]

Re: xl 800 wont plane off

Your year/model does not have a catalytic converter, so no problem there. It's easy enough to pull the water box and check for an obstruction. That's the big silver tube in the rear of the ski you were referring to. Perhaps a baffle came loose.

You do need to be careful pressurizing the exhaust as you could blow the crank seals. The way you did it sounds fine, though.

There are a number things this could be, ranging from fuel delivery (carbs, fuel filter, etc.) to an electrical CDI problem. At the very least, the carbs should be rebuilt every 2-3 years and I agree this is a good place to start, including the fuel filter. While you have the carbs off, you may want to pull the intake and check the reed valves. This is probably not your problem, but it's a good idea to check them. SBT sells new intake gasket kits, and carb rebuild kits.

A shop manual will help you with the troubleshooting process, and show you how parts disassemble.