300/440/550 Something wrong with my engine, video included. Any advice?

[OpusV]

http://www.youtube.com/watch?v=88ti6pFIg8o&feature=share

The engine has this really harsh "brap brap brap" to it, it never did this before. It's so loud that my right ear(the one closest to the exhaust) is ringing after a few min of riding. Also it's been very difficult to start(as you can see in the video), and it dies randomly about 2-5 times per tank. It usually takes twice as long to start, so this was one of the better times.

 

[dbattersby20]

does it still perform the same? i would check for an exhaust leak or something similar.

 

[NewName]

Check the Reeds maybe...

 

[Kohldanielzimmer]

What waterbox is in there? Might be a broken baffle... The hard starting could be quite a few different issues. Check the easy stuff, plugs, compression, carb. Then move on to a leak down test if hard starting symptoms persist.

 

[OpusV]

does it still perform the same? i would check for an exhaust leak or something similar.

This only happened once, but I had a really strong vibration in the tray and a loss of power, I was going nearly full throttle and barely staying on top of the water. I hit the kill switch and just floated around for about 3 min then started it up again. It felt weak but I was able to make it back to shore(was about half a mile out). But after that, it ran strong just..very very loud.

 

[High Speed Industries]

Do not run it anymore! I bet it's a crank bearing. If you run it any longer it will break a bunch of expensive stuff. Pull your plugs and turn the engine over by hand using the drive coupler. Does it feel smooth? Can you even turn it?

 

[Rompn]

Check the Reeds maybe...

Unless it has a swapped in reed engine, based off of the right hand exhaust, it would have a piston port engine, no reeds.

 

[Rompn]

What waterbox is in there? Might be a broken baffle... The hard starting could be quite a few different issues. Check the easy stuff, plugs, compression, carb. Then move on to a leak down test if hard starting symptoms persist.

I agree with this.
What mods are done to the engine? When was the last rebuild? Broken baffle in the waterbox is a definite possibility. Pull it and shake it. Shouldn't be any noises. Try swapping another one in just to see if it makes a difference in power and ease of starting.

 

[screaming440]

X3 for the water box baffle. it can cause both. plugs the exhaust and the ski wont run cuz of too much back pressure and it will sound just like that when it is not pluging the exhaust.

however you should besure that you have good water flow too. if the water box is dry it will be loud.

 

[OpusV]

I agree with this.
What mods are done to the engine? When was the last rebuild? Broken baffle in the waterbox is a definite possibility. Pull it and shake it. Shouldn't be any noises. Try swapping another one in just to see if it makes a difference in power and ease of starting.

I don't think it's been rebuilt, and the previous owner didn't mention any modifications, from the outside I can tell there's a new carb and flame arrestor, and a coffmans half pipe, I'm not sure what else has been done, it's got a lot of top-end speed, I rarely go above 40% throttle, even on flat water, but that could be because I'm still new =P

I've taken it out 3 more times since the video, I noticed the noise only happens when it's IN water. If I have it connected to water on dry land it sounds normal, so I'm pretty sure it's the waterbox...right? The waterbox is stock, and I'm trying to hold-off on upgrades and just save for a 800, but would it improve low-end power? if so, I might look into getting a better one. I'll take it out in the next couple days and shake it, check for any weird sounds.

 

[Rompn]

I don't think it's been rebuilt, and the previous owner didn't mention any modifications, from the outside I can tell there's a new carb and flame arrestor, and a coffmans half pipe, I'm not sure what else has been done, it's got a lot of top-end speed, I rarely go above 40% throttle, even on flat water, but that could be because I'm still new =P

I've taken it out 3 more times since the video, I noticed the noise only happens when it's IN water. If I have it connected to water on dry land it sounds normal, so I'm pretty sure it's the waterbox...right? The waterbox is stock, and I'm trying to hold-off on upgrades and just save for a 800, but would it improve low-end power? if so, I might look into getting a better one. I'll take it out in the next couple days and shake it, check for any weird sounds.

Have you pulled the plugs to check and see what they look like? Compression check?
I would still pull the waterbox and shake it. There should be no rattling. If there is the baffle is broken and probably wedging itself up against the outlet causing odd noises and power variations. If it is broken then yes, even a good condition stock replacement will be a power gain over your broken stock one. However any aftermarket one will give you some slight performance gains and used ones are inexpensive and everywhere. They are louder than stock though.
The fact that it only happens in water sounds like it has to do with the engine being under load. It really could be a number of things but the waterbox is usually one of the first items to go and is easy to check.
As far as the 800 swap goes, if you can't ride the 550 engine hard as it is, an 800 is going to be a challenge. There not high rpm engines but have a lot of low-mid power. A good stock used one will run $1,200-$1,500 and then there is the discussion about swapping pumps etc. Since your new to the stand up scene I would highly recommend getting a lot of ride time under you before starting into an expensive, time intensive swap. The half pipe, carb and flame arrestor are all good mods. If it has an impeller and intake grate then your set. Just ride it.

 

[OpusV]

As far as the upgrade is concerned, I wanted to get a whole new jetski not just swap out the engine. My biggest problem so far with the 550 is the hull and lack of low end power. yea, having more skill would help, but a friend let me ride his 800 my first week on stand-ups, and even then I could see the difference. I'm 220 lbs, and the water is usually pretty crazy out here, the 800 just felt at home in the water for me. Even now, I'm much better than I was in that video, but the 550 just feels awkward after experiencing the better hull design, stronger torque, and heavier front end of the 800. If I'm just messing around in a small area close to the shore the 550 is a lot of fun to throw around, but when it comes to going out in the open ocean and managing 2-6 foot swells, constant wind and choppy water, the 800 is pretty much better in every way possible.

It'll be a year before I can buy an 800 though, I want to use that time to get better at riding the 550, I think trying to master this thing will only make the 800 easier to ride. Thanks for the advice, I have 4 days off, gonna try to figure out exactly what's going on with this thing.

 

[OpusV]

It was the baffling, changed to a coffman waterbox, sounds better but the performance is about the same. Thanks for the advice!