Video - Help me understand what is causing this?

[W3bexec]

Hopefully the experts here can help me understand this, I so appreciate this site! I'm new to jets and obviously new to troubleshooting this kind of stuff. Had the boat out yesterday and all was fine for most of the day until this started happening. I took this video of it specifically to post here as well as show the dealer if needed.

Gradually increasing the throttles up and all seems pretty normal until the port engine gets to 5K RPM. Then, just the port engine shoots up to 7-8K without any throttle applied. The quick throttle down at the end is me putting both levers in neutral. Here is the video of this:

I shutdown and checked the clean out ports. On the port I did find 2 very small twigs in there but nothing else. Afterward the problem still occurred. At that point decided to take her to the dock and wrap up the day. On the way, going about 4.5K RPM, the boat jolts a bit and I hear a clunk as see a quick bump up in port RPM, then goes back to normal. After that the issue of 5K racing up to WOT on port engine went away.

Also of note and you can see this is the video before the RPM race up occurs. Above no wake speeds the port engine is pretty consistently 300-500 RPM lower than starboard. Not sure if its related to this or not. Anyway, annoying as heck and will have a the dealer look.

 

[robert843]

Hmm this one is interesting. I'm interested to see what everyone comes up with the strange thing to me is the only reason I could see it shooting up like that is the load to come off the pump but not sure how its possible so I know that is not the answer.

 

[bronze_10]

Something in intake grate allowing enough water for slow speed but not enough at higher speed?

 

[haknslash]

It's almost as if your port cleanout plug is sealing from idle and then anything beyond 5k RPM it can't handle it and just acts like the plug isn't sealing. Is there a bunch of water in the port cleanout tube after this compared to the starboard tube?

 

[seadude]

Classic cavitation of that port impeller. If you punch it from idle does it do it immediately?
If there are no obstructions or hidden debris in the pump (easy fix), a poor seal somewhere can cause this.

 

[swatski]

Classic cavitation of that port impeller. If you punch it from idle does it do it immediately?
If there are no obstructions or hidden debris in the pump (easy fix), a poor seal somewhere can cause this.

I agree.
Look through the steering nozzle with a flashlight, then from under the boat through the intakes. You may have have something obstructing the stators - stuck between the impeller and the stator segment. There is no way to clear that through the cleanout ports. Blast it on the water. If it continues, just pull the pump, takes about 10min.

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[buckbuck]

I concur with @seadude. Looks like a classic 'piece of wood lodged on the impellor' cavitation. From your description it just came off and the problem went away. No worries and it will happen again.

 

[W3bexec]

It's almost as if your port cleanout plug is sealing from idle and then anything beyond 5k RPM it can't handle it and just acts like the plug isn't sealing. Is there a bunch of water in the port cleanout tube after this compared to the starboard tube?

This is the second time I have taken the boat out and both cleanout tubes have been full. To be clear, this is the forearm length part of the tube on top of the plug. In another thread someone else was asking about this exact thing and the general consensus seemed to be that this was normal?

 

[W3bexec]

I agree.
Look through the steering nozzle with a flashlight, then from under the boat through the intakes. You may have have something obstructing the stators - stuck between the impeller and the stator segment. There is no way to clear that through the cleanout ports. Blast it on the water. If it continues, just pull the pump, takes about 10min.
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Thanks @swatski ! Boat is at storage now but I'm going to drive over and look at it.

Any thoughts on this general difference in RPM sync between the two engines? I think I have seen other posts about this and it was an adjustment of some sort.

 

[bronze_10]

When u come off plane water will rush onto the swim deck and some will go into the plug tube... If u pull your boat out and the water says on top of the plug that tells me it is seal properly.. I had one that would hold water and the other one was always dry. I found out the sealant between the tub and the cast aluminum part the plug locks into was gone and water was running into my bilge...

When our boat comes out of the water we pull the clean out plugs to let the water out and set the plugs on top of the tube sideways... Not installed. I install then before I launch the next time..

Isn't that right @justason?

 

[justason]

When u come off plane water will rush onto the swim deck and some will go into the plug tube... If u pull your boat out and the water says on top of the plug that tells me it is seal properly.. I had one that would hold water and the other one was always dry. I found out the sealant between the tub and the cast aluminum part the plug locks into was gone and water was running into my bilge...

When our boat comes out of the water we pull the clean out plugs to let the water out and set the plugs on top of the tube sideways... Not installed. I install then before I launch the next time..

Isn't that right @justason?

200% agree. Comes from swim deck. And yes the plugs when not is use or they will swell and only come free after much curseng. Assuming you have the press in plugs. I havent experienced the newer screw in plugs

 

[robert843]

200% agree. Comes from swim deck. And yes the plugs when not is use or they will swell and only come free after much curseng. Assuming you have the press in plugs. I havent experienced the newer screw in plugs

Your not missing much the new plugs are going to have similar issues. I left mine in all last year as I kept forgetting to pull them before the marina would put it up in dry stack. This spring they were a pain to get out and required some some cleaning to get them sliding back in and out easy. Sand and grime gets caught in the screw part and makes it tough.

 

[W3bexec]

When u come off plane water will rush onto the swim deck and some will go into the plug tube... If u pull your boat out and the water says on top of the plug that tells me it is seal properly.. I had one that would hold water and the other one was always dry. I found out the sealant between the tub and the cast aluminum part the plug locks into was gone and water was running into my bilge...

When our boat comes out of the water we pull the clean out plugs to let the water out and set the plugs on top of the tube sideways... Not installed. I install then before I launch the next time..

Isn't that right @justason?

Great idea and at that angle it also allows the water in the plug to dribble out as well and I can then close the hatch. I have the newer twist lock plug.

 

[haknslash]

This is the second time I have taken the boat out and both cleanout tubes have been full. To be clear, this is the forearm length part of the tube on top of the plug. In another thread someone else was asking about this exact thing and the general consensus seemed to be that this was normal?

Mine has never been full of water unless my cleanout plug wasn't seated. If water is filling the tube IMHO it means the plug(s) aren't sealing because water doesn't normally go to the upper swim platform when coming off plane as it takes A LOT for that to happen, like literally trying to force water over that high (reverse sub move or a lot of ballast). I can hot dog my boat real hard and my upper swim deck is usually dry with the exception of a few drops. It's never soaked like the lower swim platform always is. I'd love for someone to shove a waterproof light and a GoPro in the tube just to see what is actually happening. My guess is the plugs don't seal completely when under high load.

 

[Jameson Clark]

Mine has never been full of water unless my cleanout plug wasn't seated. If water is filling the tube IMHO it means the plug(s) aren't sealing because water doesn't normally go to the upper swim platform when coming off plane as it takes A LOT for that to happen, like literally trying to force water over that high (reverse sub move or a lot of ballast). I can hot dog my boat real hard and my upper swim deck is usually dry with the exception of a few drops. It's never soaked like the lower swim platform always is. I'd love for someone to shove a waterproof light and a GoPro in the tube just to see what is actually happening. My guess is the plugs don't seal completely when under high load.

I have only had mine out 3 times so far but everytime they are full to the top with water at the end of the day. When I go out next weekend, I am going to make sure they are dry before launching and keep a close eye on the platform and run on plane for a couple minutes, then come off plane slowly to ensure no water gets to the top platform and check them again.