Airborne 242

[cane.mba]

So we were out on the lake heading back from dinner at one of the marina restaurants and I got behind a very large (at least 40') yacht. When I went to cross his wake and go around him the boat leapt out of the water, I was a little surprised as we were only going about 30 with 6 adults on board. However once the boat landed I had no thrust, plenty of RPMs. I shut down, and jumped back to check the plugs, thinking I had blown both. However, other than being covered with water both plugs were seated. Worked the throttles back and forth thinking maybe the buckets just got pushed up, started her back up, and she ran fine. Freaked me out for a 1/2 a second, but instead of panicking, I just ran through all the common things I've read about here and we were back up and running in under two-three minutes.

Still not 100% sure of exactly what happened, but I'm thinking maybe I just got enough air into the jets that I needed to shut down for a moment and let the water flow back in.

 

[cane.mba]

It was freakin awesome though!

 

[Andy S]

I have done that on a PWC before, you lost suction on the jet pumps and it took a moment to regain suction.

 

[cane.mba]

Thanks, that's what I thought once I reseated the plugs.

 

[Bruce]

I have had the jets come out of the water and suck air several times. It is either fun or scary to hear them spin up in the air. But I have never had a loss of thrust.

I think you must have experienced some sort of extreme cavitation.

 

[davel501]

I have done this a few times. No loss of thrust, just lots of angry looks.

 

[Ronnie]

I have done that on a PWC before, you lost suction on the jet pumps and it took the moment to regain suction.

X2.

Also, I've always been told to get off the throttle, if you have time to, when you get air (usually on a pwc), this will reduce the load shock to the propulsion system when the the boat hits the water and suddenly starts to pump it again.

 

[Julian]

So how long did the boat have no thrust? I've done this before, and no thrust for 1/2 second is normal (while you are in the air)....

 

[jcyamaharider]

I have had this a couple of times and a couple times while in the water with an emergency back up once. The pumps just came unloaded and wasn't pulling in water. The plugs had nothing to do with it. If you just let it idle it would have fixed itself in about 3 seconds.

 

[Geiger41]

What you had there was called fun !!! No need to worry

 

[cane.mba]

Ok, I'll blame some other jetboat site that's not nearly as awesome as this one for making me overly paranoid about plug blow outs. This paranoia, made me over react, and shut down to begin troubleshooting. Honestly it was probably 5-6 seconds or so before I shut down the engines to verify the plugs. Now when I pulled the plugs they were covered to the very top with water and it drained rapidly.

Hypothetical Question
I wish I had paid more attention, but (and I may be wrong) I don't remember water being in the tunnels, when I drained the plugs. Is it possible to get vapor lock or a bubble in the tunnel that would prevent water entering? Could my draining the plugs have primed the tunnel? I'll admit the aft may have been over a wake again, so that may have resulted in less water in the tunnels. So hypothetically can you "vapor lock" the tunnels?

I'm pretty sure that fluid dynamics combined with gravity and displacement would indicate water would be forced in through the intake and naturally flow out through the jets since the jets would be the highest point.

I may have to find a giant house boat or another yacht this weekend to repeat this experiment time and time again, documenting my scientific findings again, and again, and again.

 

[jcyamaharider]

LOL, experimenting is fun!!! The water on top of our cleanout plugs is a good thing, if there isn't water there that may mean the plugs do not have a good seal and might cause a little cavitation. Mine has this from time to time and I need to order the rebuild kits. I don't think you can vapor lock the tunnels, if another wave was present then it might have taken a little more time for the pumps to prime themselves, other then that don't sweat it. I remember jumping the XR to the point to where I could here the pumps unload as I backed out of the throttle. That boat was fun with bigger wakes!!

 

[Geiger41]

Water in the plug area is normal. No worries

 

[Glassman]

Only 30????

piker......next time, punch it and give the crew a treat!

first to loose their dinner cleans the boat!

 

[cane.mba]

@Glassman I told everyone after dinner if they gotta go get it over the side, and they have to clean it! The ride over to dinner was the typical weekend, very rough, but the ride home was really smooth with maybe 10% of the boats we saw before, and the wind had died down.

This was also our first time in three years to have the boat out after dark. It seems all the really bad accidents on our lake occur at night, so we avoid the higher risk situation. Discounting the 300 million bugs sitting at the waters surface, it was totally killer. So now I'm researching LED lighting mods, since you can't run the courtesy lights without the tower lights (seems totally backwards, you can run the tower alone, or tower with courtesy, but you can't run just the courtesy lights) and an underwater LED light solution.

Our lake is pretty murky with visibility being 5-6' so I think I'll have to find one or two strong lights.

 

[cane.mba]

LOL, experimenting is fun!!! The water on top of our cleanout plugs is a good thing, if there isn't water there that may mean the plugs do not have a good seal and might cause a little cavitation. Mine has this from time to time and I need to order the rebuild kits. I don't think you can vapor lock the tunnels, if another wave was present then it might have taken a little more time for the pumps to prime themselves, other then that don't sweat it. I remember jumping the XR to the point to where I could here the pumps unload as I backed out of the throttle. That boat was fun with bigger wakes!!

I'm used to water over the plugs but this was the first time, it was to the top of the plug holes. Usually we only have 3-4". My wife was pissed because the entire swim platform including the upper seats were soaked. The water is only 81 almost 82 degrees (perfect to me, not to hot, not too cold very refreshing) so she won't get in yet (Florida girl, she likes the water hot).

 

[Glassman]

@Glassman I told everyone after dinner if they gotta go get it over the side, and they have to clean it! The ride over to dinner was the typical weekend, very rough, but the ride home was really smooth with maybe 10% of the boats we saw before, and the wind had died down.

This was also our first time in three years to have the boat out after dark. It seems all the really bad accidents on our lake occur at night, so we avoid the higher risk situation. Discounting the 300 million bugs sitting at the waters surface, it was totally killer. So now I'm researching LED lighting mods, since you can't run the courtesy lights without the tower lights (seems totally backwards, you can run the tower alone, or tower with courtesy, but you can't run just the courtesy lights) and an underwater LED light solution.

Our lake is pretty murky with visibility being 5-6' so I think I'll have to find one or two strong lights.

I hear ya! I ran separate courtesy lights and added 3 forward facing and two rear facing lights on the tower for our evening cruises. I'm considering swapping them out for LED lights since they suck up a ton of power - I only run them when I'm WOT - there is no enforcement at night (at least not in the last 15 years) up river where I boat and the river is empty, so running at night is a blast.

 

[davel501]

X2.

Also, I've always been told to get off the throttle, if you have time to, when you get air (usually on a pwc), this will reduce the load shock to the propulsion system when the the boat hits the water and suddenly starts to pump it again.

Good point on the throttles. I think most folks would pull them back to neutral instinctively before the boat even hopped if they are used to operating in rough water but the first time seeing those conditions you are along for the ride.