WaveRunner GP800R - Loss of Power

[mrkron]

I have a 2003 Yamaha WaveRunner GP800R. I bought it last spring and it worked great for most of the summer. Then during a long weekend of perfect performance at the lake I put it in on the third day and it fired right up and I took off. However after about 5 minutes into riding it chokes down and dies. It cranked fine, but I could not get it to start again. After towing it back to shore we finally got it to start, but it idled very roughly and would die if I gave it any gas or applied the choke.

After I got it home I changed the plugs and fuel filter and treated the gas with Sea Foam. We got it running great on the trailer, but once I put it in the water under load it would bog down. It runs stable, but it has no torque or power. When I bought it, it could launch me out of the hole at take off and top out around 63 mph. Now it slowly climes up to about 40 mph and that's all it can do.

Sorry for the long description, but any suggestions would be greatly appreciated. Thanks!

[torquenut]

Re: WaveRunner GP800R - Loss of Power

What is the compression?

[mrkron]

Re: WaveRunner GP800R - Loss of Power

Well I checked the compression and I had around 90 psi in the front and 0 in the rear!! I didn't need an internet forum to tell me what that meant. I pulled the head and found the problem. I have about a 1/2" chip out of the rear piston!! (See pictures)

I feel stupid, because this should have been one of the first things I checked. I'm sure I did additional damage to the cylinder running it like this. I think I just hoped it was somthing minor and didn't want to really know what the compression was.

I guess I'll be taking it off to the shop.

[Madfish]

Re: WaveRunner GP800R - Loss of Power

Get yourself a cylinder exchange kit from SBT. Comes with everything you need for a new top end - new cylinders, pistons, rings, gaskets.

[mrkron]

Re: WaveRunner GP800R - Loss of Power

Do you know what would have caused this piston to fail? It is only an 03' and it doesn't have that many hours on it. I would hate to repair it and have it happen again because I missed something.

[Madfish]

Re: WaveRunner GP800R - Loss of Power

When you take your cylinders to SBT for exchange, ask one of the techs there to take a look at your cylinders and give you an educated guess as to what caused this problem (lean condition, water ingestion, oil injection failure). Those guys see hundreds of engines every year and I would listen to them. My personal recomendation would be to check, clean, rebuild carbs, re-set high/low speed screws to eliminate possibility of lean condition, check all your cooling lines and hose clamps, and if you have not done so yet, definitely remove oil pump, install block off plate, and go with premix. That way, you are in control, and 100% certain the engine is getting the lubrication it needs, and not relying on oil injection.

One of my favorite questions is when someone asks "how do I know if my oil injection system is working?". You'll know when your engine blows, and you find yourself down at SBT pulling your credit card out of your wallet.