Air leak - revs high outof the water

[MarcPete]

When out of the water, the engine revs very high, out of control. Am I correct in 2 things?:
1. I could have the idle screw on the throttle set too high? If it is, why would this cause it to rev sooo high all of a sudden?
2. Could be an air leak? If it is an air leak, what are the various things to check?

I've done a lot of work on the engine recently and I did move the idle screw up (yes, an easy test to screw it back down, but I'm more curious to know how this could affect it) and I've had the engine apart recently for un-related issues (had a bad cylinder) and I had everything apart for it (cylinder block off, head off, carbs off, intake manifold off = it could be many of things for an air leak). So, i was wondering what specifically to look for when searching for an air leak.

Runs great in the water, so I'm also wondering why it doesn't do this in the water, but does out of the water...

Thank you anyone for your help.. I'm knew to PWCs and am trying to learn as much as I can.

[driftmaster]

Re: Air leak - revs high outof the water

Lean hang, also could be crank seals or jetted lean. Always replace crank seals on a 2 stroke when you have a engine tore down. Good news is you can pop of the bottom case and replace them without removing the top end.

Always a good idea to pressure test rebuilt engines.

[MarcPete]

Re: Air leak - revs high outof the water

What is Lean Hang?

[driftmaster]

Re: Air leak - revs high outof the water

It won't come back to idle

[driftmaster]

Re: Air leak - revs high outof the water

You can try riching up the high and low a 1/4 turn and try. Keep a towel to stuff in carbs if it runs away.

[Grumpy Old Guy]

Re: Air leak - revs high outof the water

First turn idle down.

If a motor "runs away" out of water,pull teather cord off & pull throttle wide open,it will shut down.

The reason it does it only out of water is there is no load on the motor when out of the water IE pump in water.

[Bionic racing]

Re: Air leak - revs high outof the water

Check base gasket air on your Yamaha , 701?

[MarcPete]

Re: Air leak - revs high outof the water

Is an XL 1200 (3 cylinder).
I will turn the idle down first. It didn't do this prior to the engine being torn down. So, I was thinking I maybe didn't put a hose on properly somewhere or it could be the gasket between the cylinder block and crankcase. The crankcase was untouched and didn't leak before, so I don't know if it would be the crank seals

[Grumpy Old Guy]

Re: Air leak - revs high outof the water

Should be barely idiling out of the water

[MarcPete]

Re: Air leak - revs high outof the water

I turned down the idle and when I flushed my engine (out of the water), it did not rev high/out of control. So, i guess I had the idle set too high. So, now I'm wondering what are the mechanics behind a high idle making it rev out of control like that... does it let in too much fuel or air somehow? Just curious