Jet pump damage.

It is understandable that rocks or other debris sucked into the jet pump can damage the impeller. That is easily repaired or replaced.
How about the pump internal walls? Especially in the area where the impeller is located?
In some pump designs this section of the pump is separate, and can be disassembled and repaired or replaced; in others it is not.
How much of a risk is it, buying a "unibody" jet pump?
Does it often happen that the impeller housing walls get so damaged that the housing needs to be replaced?

 

Very seldom, in my experience. The impeller blade leading edges are the vulnerable parts. Some jet units have a "safety hub"; a plastic bushing that breaks when the impeller is jammed by debris.

 

In rough usage jetboats(i.e. shallow rocky rivers) it is almost a non issue. American style pumps typically only require the usual impeller/wear ring servicing at intervals depeandant on how rough you are with the boat/pump.

Mercury Sportjet style pumps, which have proven surprisingly durable in this type of use, do expereince wear ring housing wear as you describe but its common practice for shops to bore out the factory aluminum housing and install a stainles steel liner which greatly lengthens this parts life(by about 4 times) additionally this ss liner can usually be replaced making the factory housing last nearly forever.

Generally most information on the internet grossly over emphisizes wear and tear on a jetpump, especially in the deep water/lakeboat crowd. If they wore out half as easily as most said the shallow water guys would be buying pumps left right and center which is just not the case. Jetdrives can handle alot more than most people ever put them through and they still remain one of, if not the, least expensive drive systems to maintain

Cheers

 

All the technical details are irrelevant.

The tolerance between the impeller and the pump body is.

If its not to specs then you have to do what you have to do, what ever that may be --re sleeve or buy new body.

 

Life span depends on the material mostly. If you have an imitation Berkeley jet from CP-Performance, the impeller bowl will be eaten by seawater even if you do nor use it at all.

If the proper alloy is used, you just need to replace the wear ring from time to time. Real damage will only occur when the pump is used without an intake grid in shallow waters where the pump can gobble up large pebbles or other hard debris.