Cavitation and Engine shut down.

[ZippyBoater]

OK guys. had a rough weekend on Lake Gaston. My port Jet has been experiencing cavitation recently. It is worse when I am loaded with passengers. I get no hole shot at all anymore. I hit the throttles and the port engine goes to max rpms and it sounds like a really bad blender. I have checked the impeller and there is nothing stuck and the edges are pretty smooth for an 11 year old boat. There is no play in the shaft. I can't find any issues. This started this spring when I put the boat in the water. Could it be the silicone or something else?

The engine shut down happened when I took the boat 15 miles down the lake to visit some friends. We don't normally venture that far from home. We got to within half a mile, I slowed to navigate into their creek and the port engine just stopped. No warning lights no nothing. I let it rest for a few minutes and tried to figure out what caused the shut down and was able to start it again. I motored on and it shut down again. Checked oil, pulled the clean out plugs and nothing. This time the stop was longer. Engine fired up and I limped to my friend's dock. Engines cooled down for 3 hours while we were there. The trip home was uneventful. We stopped half way home to let the engines cool just in case. I am thinking the auto shut down was due to over heating. Any other ideas?

 

[sunbyrned]

This has happened to me, although my engine never stopped. Regarding the bad blender sound, I removed the impeller (found no debris) and put it all together again. That fixed it for me. I’m thinking the grooves weren’t in sync.(?)

 

[ZippyBoater]

This has happened to me, although my engine never stopped. Regarding the bad blender sound, I removed the impeller (found no debris) and put it all together again. That fixed it for me. I’m thinking the grooves weren’t in sync.(?)

I am trying to avoid pulling the boat out and pulling the pump. What do you mean by the grooves being in sync?

 

[sunbyrned]

I guess the technical term is "splines". They're on end of the shaft that goes into the boat. They can become out of sync. I tried to find some pics to show you what I'm referring to. See if this helps any?

https://jetboaters.net/threads/drive-shaft-and-impeller-splines-stripped.23704/

 

[ZippyBoater]

I guess the technical term is "splines". They're on end of the shaft that goes into the boat. They can become out of sync. I tried to find some pics to show you what I'm referring to. See if this helps any?

https://jetboaters.net/threads/drive-shaft-and-impeller-splines-stripped.23704/

Thanks. I hope my problem isn't that bad.

In my situation, once I get on plane, there is no problem until I do something to come off plane like turning hard. Did you experience that?

 

[Scottintexas]

https://jetboaters.net/threads/cavitation-missing-sealant-in-pump-grate.884/

When my silicone came loose missing, I didn't have any initial power and it would vibrate/shake and sound like the engine was coming apart.

I think your sucking air somehow,

.

 

[sunbyrned]

Thanks. I hope my problem isn't that bad.

In my situation, once I get on plane, there is no problem until I do something to come off plane like turning hard. Did you experience that?

That is not what I experienced. I could never get to plane but the sound was identical to what you’re describing.

 

[Scottintexas]

Thanks. I hope my problem isn't that bad.

It probably isn't, that was a BRP set up, in 12 years with Yamaha I don't think I've heard of someone stripping or "jumping" their splines, if anything they get seized in place and you have to pull them out with a come-along or attached to a vehicle,

at this point, if you've given it a day and the problem is still there I think you need to pull the boat and get visual confirmation what's going on, when you pull the impeller you'll clearly see the just and your silicone sealant,

if you don't see anything obvious i'd put it all back together and give it a test run, it's amazing how many times stuff gets stuck and then just floats away before we ever get confirmation what the problem was,


.
.

 

[ZippyBoater]

Thanks guys. I got in the water the other day and got under the boat while it was on the lift and I couldn't see anything. I probably need to pull the pump and check the silicone better as well as the wear ring. I know that it sounds like I am sucking air. I just don't know where it could be coming from.

Are there any videos on how to reseal the pump?

 

[Scottintexas]

Are there any videos on how to reseal the pump?

not that I know of off-hand, we've had members do things from
slather household silicone (me)
to taking the ride plate off and reseal with 4200 or 5200 (don't quote me on that) (I think Ronnie did that on his old boat)

I'd suggest just getting a look at it first, I chose the silicone just to see if it made an improvement before pulling the ride plate and all the work involved, turns out it's held for many years now,




.

 

[ZippyBoater]

not that I know of off-hand, we've had members do things from
slather household silicone (me)
to taking the ride plate off and reseal with 4200 or 5200 (don't quote me on that) (I think Ronnie did that on his old boat)

I'd suggest just getting a look at it first, I chose the silicone just to see if it made an improvement before pulling the ride plate and all the work involved, turns out it's held for many years now,




.

Thanks. I am assuming that I will have to pull the pump and impeller to fix the silicone?

 

[Scottintexas]

Thanks. I am assuming that I will have to pull the pump and impeller to fix the silicone?

depends on where and how much, I did all mine from the bottom through the intake grate before I knew better,

it's only 15 minutes to pull the pump and good experience, I'd suggest it if nothing more than to give you a better viewing angle than on your back,


.

 

[ZippyBoater]

depends on where and how much, I did all mine from the bottom through the intake grate before I knew better,

it's only 15 minutes to pull the pump and good experience, I'd suggest it if nothing more than to give you a better viewing angle than on your back,


.

Thanks. Now I have to find the time to pull it out of the water and a weekend that my wife doesn't have us entertaining people on the boat.