Introducing myself and asking my first question.

[Mr. Sonora]

Hello, please allow myself to introduce myself. My name is Chris and I live at Lake Chapala, Jalisco, México. I am an avid off-roader and have owned numerous trucks (Toyotas and Fords), Jeeps and so on. I have recently purchased a 1998 Sea Doo Challenger boat with a single Rotax 787 engine. The engine was recently re-built, and the boat is in OK condition. I know it's going to be a project, but I decided that since we live on Mexico's biggest lake, it's absolutely a necesity that my kids (4 and 1) grow up with some water toys. So, I went ahead and bought the Challenger, it cost me about $4,700 USD with the trailer.

So on to my first question. When we were trying out the boat, it started fine, and it would drive, but it would not drive very fast, and when we put the accelerater all the way to the front the RPMS would go very high, the engine would rev very loud, but it just did not pick up speed. I almost didn't buy the boat, cuz we could just not get it to run. I was out with the previous owner, and I don't anything about mechanics, and neither did he, but he swore to me up and down the boat ran right before and even on his last trip out to the lake. He thought that it was just some minor adjustment, and we opened the engine compartment and started playing with a few things. We pulled the spark plug cables and then put them back on. There were also two things which are like black caps with a red top, which he called "exhaust valves", in spanish, and he released them, pulled them off and moved the valves under them up and down. That seemed to do the trick, and immediately the boat pick up speed and ran and handled like what I imagine it's supposed to do. We ran it for about 30 min and it worked fine the rest of the time. That convinced me that whatever it has was a minor issue and I purchased the boat. Of course, the first run I did by myself with my new boat, the same issue came up again. I did exactly the same thing he did with the "exhaust valves" but to no avail. The boat actually moves faster in Neutral than it does with the accelerator all the way to the front. So whatever the problem is, it's back....

Now on to the next problem. The only boat mechanic I know of in my town, right down the street, DOES NOT work on jet boats. Apparently these jet boats are rare in Mexico and they don't know how to work on them. There is a Sea Doo mechanic in Guadalajara that is the guy who rebuilt the engine, but he is very busy and it's about an hour drive from my house (pulling a trailer) plus he isn't cheap... so I am looking for a local guy right now for whatever issues come up. There is an ultra-light airport near my house, and they all have Rotax engines and a guy that works on them. I talked to them and they are willing to help, if they can, but they did say that boats is not their specialty. I am going to have him check it out when he gets back from vacation. However, in the mean time, I figured I would come on here and ask for advice. Hopefully someone can give me some input. The valves that we played with that seemed to have done the trick last time are these: http://www.ebay.com/itm/Sea-Doo-Rav...254&pid=100033&prg=1011&rk=3&sd=221186250431&

I am not sure what they do, but it seems that they have something to do with the power. If anyone has had similar problems and can give me some input, it will be much appreciated.

I will be asking more questions than contributing info at first because I am a total rookie on these things, but I a huge source of information for traveling, living, relocating in Mexico so if anyone has any questions on that, PM me and I am at your service. I am also a licensed Broker, so any property acquisition questions for Mexico are welcome.

Thanks and I look forward to participating with y'all in the future.

Cheers,

Mr. Sonora

 

[Dr Honda]

Welcome, and que pasa.

First... the exhaust valves are known as RAVE valves. They open as the RPM's climb, to change the port timing. Basically... when they are down... the engine makes more torque. When they are up... they help the top RPM's. If they are moving free... I doubt they are your issue.


What you are describing is called cavitation. Basically... it's like spinning the tires on your car. Too much power, and no traction. So... the question is... why are you loosing "Traction"? The most likely place is around the carbon seal on the driveshaft. If it leaks... the pump will suck air in... and you can't compress the water. (you loose thrust) Directly behind the engine... there should be a gray plastic cover. If you loosen the nuts... it will lift off. That seal may need rebuilt, or just tighten. The rubber boot holds a carbon ring. It's a loose fit... so try to pull it back a little, and see if it's warn. Also... on some of the drivshafts... there is a second clip spot for the stainless ring that the carbon seal pushes on. You can try to push it toward the rear, and check for a second spot to tighten the seal. (pic below)


There is one test. You can put a little waterproof grease on the face of the seal (between the carbon and stainless ring) The grease can help seal it. If it gets better... then it's time to rebuild the seal. (rubber boot, carbon and stainless rings, and a few O-rings)



Good luck

 

[racerxxx]

Also put some grease in the zerk fitting on the PTO to push the shaft back to tighten up the seal. Watch teh shaft move back while you pump the grease. Don't over fill the rubber boot. I can tell when my Speedster could use a pump i'll get a little cavitation.

And welcome to the forum!

 

[Mr. Sonora]

Thanks guys. I will look into this... The best way I can describe it is a slipping clutch on a car... the engine revs but it doesn't move forward. What's weird though is it doesn't always rev up that high, sometimes it does, and sometimes it doesn't. I will try what you are suggesting and then go from there.

 

[Dr Honda]

Yep.... that's exactly what hapens when that seal starts to leak. It's not enough to make it leak water into the boat. (or not much) but the pump can "Suck" the seal back... and pulls air in.

With your new description... I would just buy all the new parts, and replace them.