Cavitation / missing sealant in pump / grate // FIXED

[Scottintexas]

This was my original thread posted at YJB. I removed the intake grate on the bottoms, pulled out any loose silicone in the housing and liberally applied some household silicone over the missing areas and around the gaps in the intake great just to try to trouble shoot it and confirm if it was sealant or an impeller issue and it has held up for 3 years, aprox 150 hours. I really think the loose silicone was caused when I was pulling the other boat off the sand bar. I was really giving it some thrust and not making any forward movement and I think that caused an increase in suction pressure that pulled the silicone loose.

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Yes, it happened to me, not quite the TX_DJ 2009 saga though ! oh that wonderful month of posts!

Last night I stopped to help another boat who had ran upon a sand/gravel bar. After I got him off and was replacing my stuff I drifted on it, got disoriented and instead of powering off it went straight on, ughh. I churned up some nice red clay for about 5-10 seconds before I shut it down.

Fortunately the other boat was still there and he pulled us off. It was the end of our day anyways but when we were heading in the starboard engine had a low rumble like it was going to come apart with any rpm's over 3k. It didn't scare me near as bad as the other people on the boat since I have such a vast knowledge base from this board !! thank you everyone. I thought twig or pebble stuck in the impeller, no big deal.

Debris -Looked at it today from front and back very closely (for even fishing line or something miniscule) and see nothing stuck, the rear view I can see a few shiny scrapes on the housing were something went thru but they were very minor. I even took the intake grate off to get a better look/feel.

Impeller - looks a little dinged and dirty but pretty much like the other one

sealant - noticed two spots that look like some is missing, ran my fingers over it and remaining peices at the edge seem a little loose.

So sealant is my first guess unless someone else has a better idea. Bueller ? Bueller ?

Question, Can I pull the intake duct off /drop it straight down/ with the pump unit still attached to the boat ? it looks like I should be able to and it shouldn't be big deal in the maintainance guide, just wondering if anyone has done this.


Scott

 

[Julian]

If you are asking can you take the intake grate off....sure....

 

[davel501]

Thinking about pulling my intake grates and impellers and resealing my pumps then polishing and waxing the pumps before putting it all back together.

 

[Scottintexas]

davel501 - unless you have a specific reason, they are really dirty or your having some sort of perfromance issue I would leave them alone,

Julian - thanks for the reply, it was an old post I moved over so others could see my issue, it's fixed,

 

[davel501]

davel501 - unless you have a specific reason, they are really dirty or your having some sort of perfromance issue I would leave them alone,

Julian - thanks for the reply, it was an old post I moved over so others could see my issue, it's fixed,

At some point I want to upgrade to Solas impellers but I am thinking this may not be the year. I need to save some money for gas.

Maybe next year I can pull it apart and change the impellers and do the rest.

 

[dan144k]

My stock impellers always had a slight cavitation, (felt like in neutral or a trans slip)when I installed the Solas impellers my cavitation went away.
I used the solas impellers last year straight out of the solas box.
YS-CD-13/19 Solas Concord Impeller
YS-CD-13/22 Solas Concord Impeller

This current winter I sent them to Impros, I have them back and on my table ready and waiting to be installed, boat is in storage 7 hours away.

 

[Lspeedss]

#dan144k,

obvious jet boater question. Did you gain any speed with the Solas upgrade?

 

[Speedling]

I did.
Like 2 mph.
But the boat was a much different (better) animal. It's like throwing gears in a mustang man, just a great overall design on em. It's not so drastic that my wife noticed, but I certainly felt the boat perform differently. All depends on how bad your stock ones are.

 

[BoaterGuy]

What kind of sealant is supposed to be used to seal the intake grates? I recently lost some on one side and used 3M 4200 along the channel and this stuff closer to the entrance of the grate.

Do I need to use different stuff?

 

[Speedling]

Does it say it's ok for under water use?
Edit: permanent under water use.
Obviously a marine sealant will make it sound like it can be but you would be surprised

 

[jetboater4life]

4200 is good stuff. I have started using lifecaulk and like it as well. Either of those is better than the plain silicone that Yamaha used.

 

[beachbum]

Question regarding cavitation and sealant... Should have have sealant around the intake grate and covering the bolts that secure it?

 

[Scottintexas]

probably not, if your experiencing problems I would say to do it just to eliminate possibilities but I think you look good,

 

[beachbum]

Thanks for the quick reply scottintexas... The only "cavitation" that I felt last season was during the hole shot with wakeboarder... Just seemed to be "hesitating" with the load. I have never been in another jet boat to know how they sound and run... Enjoyed the first season and expect to enjoy this one too.

 

[Speedling]

Best way to test is to do a top speed run. If you're 45+ then you are fine

 

[KXCam22]

I have used a product called sicaflex. Comes in a calk gun tube. Basically same as 4200 but clear. When I re-re my tunnels this spring I plan to use that. I don't have any objectionable cavitation but when I had my impellers out I noticed a poor fit between the hull and the intake grates. On one spot I have a 3/8" ledge in the water flow. When I look at it again I plan (so far) to grind that down to smooth out the flow. May do nothing or may be magic but it is not right. Cam.

 

[Bruce]

I have used a product called sicaflex. Comes in a calk gun tube. Basically same as 4200 but clear. When I re-re my tunnels this spring I plan to use that. I don't have any objectionable cavitation but when I had my impellers out I noticed a poor fit between the hull and the intake grates. On one spot I have a 3/8" ledge in the water flow. When I look at it again I plan (so far) to grind that down to smooth out the flow. May do nothing or may be magic but it is not right. Cam.

I have that ledge as well. What happened when you removed it?

 

[KXCam22]

When I took my pumps out in the spring to change the cone oil I got in there with the sikaflex and filled and contoured the ledges to make the water ducts flow smoothly to the impellers. The grinding wasn't really practical. I used a putty knife and some thinner to wipe the sealant smooth and to contour it quite a ways back into the duct. It helped noticeably this year with less cavitation. Cam.

 

[Jason Smith]

So I have been fighting cavatation for about 2 years now, I believe it started happening after a rope sucked in. First thing I did was pull my factory impellers and they were really dinged up. I tried to grind and file them down to resolve the issues, but it didn't totally solve it. So I bought some Solas impellers, still had the same issues. I bought new pump housings, first from ebay (don't do this, it became MUCH worse), and then new factory ones. After this, cavatation vanished in my starboard engine, but port side still had it. Frustratrated, I broke down and bought new factory impellers. Swapped the Port side first, since that is the side still cavatating, and still the issue persisted. So I spent a few hours reading through this post, and others like it. I was amazed that people were seeing the issues be resolved by replacing missing silicone, so I figured what the heck. I pulled the grate and the intake bottom and spent hours getting the old silicone off, not a fun job. Used 4200 and sealed it all back up and took it out this past weekend.

Problem was solved! No cavatation now, 8 adults on board, dead stop to full throttle, planed out quickly and was again a joy to use my boat. So I thank you for sharing and helping us all out, I am very grateful.

My suggestion for others if they have cavatation:
1. Check for damage on impellers.
2. Get the intake smooth, including the grate.

I suspect those two will solve nearly all issues for most people. Don't be like me and go years with this issue.

 

[sjbrush]

Based on this thread I need to remove and replace all this old silicone. Wondering if I could use PL Marine Adhesive Sealant in place of silicone?

Also, below where I circled in red I have a pretty large lip. Is this normal or should it be either ground down or just smoothed over with silicone?