pump cavitation

[Mark Anderson]

I am having a problem with my jacuzi 12yj pump. my boat pulls strong to about 62 mph and then I assume the pump cavitates. It is like you put it in neutral. I bought the boat at the end of last season and just got the motor back in it after doing a few hop ups. The pump was gone through just before I got the boat and appears to be in very good shape. I inspected the impellor and it is clean and sharp. Any help will be appreciated.

[OmegaBitch2]

I used to have a YJ in my 78 Omega,best it would do was 48-50mph with stock 460BBF.Tried adding more power and same thing,instant cavitation,my pump was still in good shape too,but it just has to do with the impeller design(open)compared to closed.Did a A/T conversion and much better!!

[Lake Lifeguard]

Ive seen this happen countless times. My best guess is that at some point water to flowing past the intake grate too fast to be picked up. Once while working a drag boat race I noticed that about 3 jet boats in a row lost power and spun out to the right at exactly the same location on the course. They all had a similar hull design and were running at approximately the same speed. All three drivers described the same increase in RPMs and loss of helm control. That event convinced me that turbulance under the hull or the rapid flow of the water past the grate must have interfered with the jet's intake.

[Mark Anderson]

If water flow into the pump were the cause would a stuffer grate help? and if so who makes one for my dinosar?

[Old Guy]

Mark, I have a YJ pump that I just converted with the Aggressor kit. I was able to find a loader grate and bought it for about $85 from ????? I'll look it up tomorrow. I've been having so much trouble getting my '76 SleekCraft in the water, I don't even know if I need the loader yet. I hope to get the boat in the water in a few more days. If I don't need the loader I would be glad to sell it to you.
old

[Rexone]

Hey Mark,
We make a ramp loader for the y pump. Before we isolate that as the problem though I'd like to have you disuss it with one of our jet techs which have more experience in this than myself. If you're interested just email us your phone number and someone will get with you on it tomorrow.
Mike @ Rex Marine
www.rexmar.com (http://www.rexmar.com)

[Mark Anderson]

I talked with the guys at Rex marine and they suggested that I check the bottom for a hook in front of the pump. It is straight. While I was on the phone with them I went ahead and bought a Loader grate. Problem solved. The boat does have a hook at the rear that I would like to fill. What is the best product for this?

[pops1]

OmegaBitch2:
I used to have a YJ in my 78 Omega,best it would do was 48-50mph with stock 460BBF.Tried adding more power and same thing,instant cavitation,my pump was still in good shape too,but it just has to do with the impeller design(open)compared to closed.Did a A/T conversion and much better!!What you stated here is true. Mixed flow High Pressure vs axial(open impeller)or low lift impellers run into a wall- Add some horsepower and you add more wall. Its inharent in the design and most of these designs are based on high volumn low rpms.
Cost you $ but both A/T & Aggressor offer step up kits which convert the Y & W pumps to a higher pressure system. Starting with a impeller change, shaft,Bowl & nozzle system and complete rebuild of remaining (existing) parts.
If you own a "W" pump, we at aggressor have released a new Mod Kit for this pump which modifys the shaft and bowl, a new designed impeller & wear ring are added and a rebuild to the balance. -This mod. has shown Good numbers- big hole shot @ $800.00 available through any authorized Aggressor Dlr. Dave