Cavitation

[Brmorganjr]

Ok...at the end of last year I sucked up a chit load of weeds, couldn't even clean enough out and had to limp to the dock, the next week, I got in there and cleaned it all out....took it for a test run and still cavitating some, so came home and pulled the grates and replaced some of the silicone...today was the first chance I had to test after that...no cavitation at low or high RPM....but if I try to hold at mid or gun it...I have cavitation in that mid range....roughly 5k RPM. you can hear it lose it's grip, but in a few seconds it loads...?

Suggestions? Did I tweak the port impeller? There is nothing stuck between it and the housing....

 

[Julian]

Are you sure its cavitation? I ask because last summer I thought I had a problem with my port pump and even went so far as to pull it off and check the wear ring....nothing. So I changed the plugs...and voila...problem solved. If it can't be solved with a noodle, change the plugs! LOL

 

[itsdgm]

I doubt that weeds could hurt the impeller. But maybe there's a tiny gap still in the silicone, or possibly a weed/debris still in there?

 

[KXCam22]

I get some random cavitation from time to time. Last time I had the pumps out I notices that the fit between the fiberglass hull and the jet housings was done by a chimp, lots of things not lining up and leaving square edges to cause turbulence in the water flow. This spring I plan to get in there with my grinder and smooth the edges to make a nice smooth flow path and then redo the silicone with 5200. Hopefully that will do the trick. Cam.

 

[HidnNOS]

I purchased my boat from Ronnie, at the time it had a cavitation issue he later corrected, for which Im forever gracious! My point, if you can maybe get a good camera in the grate and take pics of all seal areas as did I, he or others can point to problem areas that I never would have seen.

 

[Julian]

@HidnNOS So was caulk sealing the cause of your cavitation?

 

[Brmorganjr]

@Julian I changed the plugs right before running this time, still does the same.

 

[Julian]

If you can't see anything from through the cleanout, or through the grate. You next step is to pull the pumps. Sounds really difficult, but really it is probably an hour job. Disconnect the linkages and undo 4 bolts and slide out. You may need to "encourage" it a little to slide out.....mine came out after a few taps with a rubber mallet. Others have had to be more creative. I've had cavitation because of a bit of fishing line!

 

[Brmorganjr]

Yeap, I think that is the next step, after redoing the silicone it got rid of it at wake speed, maybe I missed a spot. laying under the boat working through the grate is not the best way to be able to see everything...LOL

 

[Julian]

Yeah it ain't easy to do that is for sure! As I'm sure you know....lower the bow as low as you can to give yourself max maneuvering room under there. It could well be a bit of uneven silicon.....

 

[Scottintexas]

my cavitation issue was because of loose/missing silicone after I pulled somebody off a sandbar and used alot of thrust going nowhere. Maybe when you had the weeds in there it caused additonal suction that broke some silicone free. Some of mine looked good but you could pull on it and it would come up a little bit.

another thing could be, if that was your first trip out with new plugs maybe one of them is bad or not gapped properly,

 

[HidnNOS]

Yes, there was an issue with the seal around the driver side pump. There wasn't a smoking gun/spot and when I bought the boat I wasn't even positive that was the cause of the issue. Ronnie smoothed every surface and after it was all over it was good. Before if you left from a stop at anything more than a creep it would cavitate badly. If you slowly got up to speed, then hammered the throttle is was a non issue. Just getting under initial acceleration. This being my first jet boat I didn't know for a fact this was the issue. After Ronnie's repair and all I've seen since then It's more clear. One thing, while Ronnie was doing the repair I would compare to the other pump seal, don't do that. @Ronnie was just sure one of the seals was the issue so he smoothed EVERY edge/corner under the one pump/gate and it's fixed. Looks NOTHING like the passenger side but neither cavitate now.

 

[txav8r]

Just looking at the silicon, it is hard to tell if you have a problem. And as julian said, pulling the pump is an easy job to confirm you don't have a small piece of something in the pump. Then, look to the grate, the intake tunnel, and anything that can disturb the flow of water into the pump. Get a very bright trouble light or something to help illuminate the area well. Get a mechanic mirror too. And then search it out pretty good for even the smallest piece of loose or missing silicone. All it takes is an edge to create a ripple in the water flowing through and to create some bubbles. It seems that much of what I looked at in mine was not smooth, but didn't cause issues. But one day, I did have an issue and I found a little piece of silicone coming loose that was more over smear onto the hull. It was loose and probably flapping. I just pulled it off and never had another issue. The thin places where the silicone is smoothed to the edge can weather and start to peel and vibrate as your moving.

 

[majsa]

Yeap, I think that is the next step, after redoing the silicone it got rid of it at wake speed, maybe I missed a spot. laying under the boat working through the grate is not the best way to be able to see everything...LOL

If you pull the pumps, let me know. Been meaning to do mine and I'd like to see/help with it and if you are still in Castaic, You are plenty close

 

[jdonalds]

My cavitation problem was corrected with sealing up small spots near the pump. I pulled both pumps and sealed it up all in less than an hour.

Reference these photos -> http://jdonalds.smugmug.com/Boats/Pump-Removal/23215801_Dn8g6J#!i=1871556138&k=RmhwG6Q