worn impeller

[rmclague]

I have a 355 olds in my boat with 12jc pump.
The boat will do 60mph on a good day with a tail wind, if you know what I mean. This is WOT. This is plenty fast to have fun, or at least it was! Now I want more speed. The motor was In the boat when I got it Last year, and I do not know much about it. It has a nice lope so prob has a mild cam. I know that my impeller is worn because when I look up from the intake grate with a flash light the edges of the impellor blades are haggard and beat up. So how big of a deal is this in terms of speed/performance? How much speed could I reasonably expect to gain by relacing my worn impeller. Also I know most boats are running big blocks, would my money be better spend working on the 355 or stepping up to a 455. also bear in mind this is a good looking/running boat but i only have about $3500 in it and dont have thousands to spend. What do you think?

[Jetmugg]

Work on the pump first, then add more power if necessary. If you can see that the leading edges of the impeller are beat up, then there is also a good chance that the tolerance between the impeller and wear ring is also shot. If you don't want to spend much, and you are mechanically inclined, you can buy a kit and do the pump work yourself. However, don't expect professional results, or 80 mph. If you can afford to spend a little more, send the pump to one of the well known pro shops, and have them do the work. Most of them have been doing it for decades, and know how to make a jet pump perform.
If that doesn't satisfy your need for speed (and when is it ever satisfied?), then a step up to a 455 Olds is a very good one for a boat with a small block Olds, and probably not all that expensive. (again, don't expect to bolt it in and run 80.) I've been there and done that with respect to the pumps and the engines, and now I have a professionally built pump and a healthy 454 Chevy engine.
SteveM.

[SoggyJet]

If you decide to change engines think seriously about going BBC instead of Olds. Many more marine and performance parts available and they are usually cheaper than parts for Olds. Any money you save by reusing the bellhousing or other parts will get quickly eaten up when you try to make the Olds live at the higher RPMs. As Steve would say thats my $.02 worth.
Doug McCoy

[Caribbean19']

If your impellar is worn, throwing more power at it may actually make the jet appear to perform worse. For my boat, my first goal was to make the pump perfect, see what improved and then increase power.

[froggystyle]

Good advice Carrib...

[roostinyahoo]

I second the above replies, or third, or... Any way, I went through my pump, a berc. 12JE, and it wasn't that challenging, mentally or financially! You can get the kit from CP or one of the other guys for around $500 or less. If you do I would have your shaft turned and add a stuffer. Really tightens it up. As far as the motor goes, if you really want an olds 455, I have one, built. I replaced it with a 454 chev. The oiling problems bothered me. I might make you a deal.

[rmclague]

Thats about what I figured. Istill wonder about the relationship of impeller wear vs speed. In otherwords am I going to spend 2-3 days tearing into this thing and $300+ dollars only to see a 2-3mph diff or will I even notice?
Also how do you measure impeller pitch or are they marked/stamped when you get them out?
Thaks for the great advice I know the first thing to do when you pick up a new hobbie/vice is to talk to people that are in the know.
[QUOTE]Originally posted by Jetmugg:
[B]Work on the pump first, then add more power if necessary. If you can see that the leading edges of the impeller are beat up, then there is also a good chance that the tolerance between the impeller and wear ring is also shot

[SoggyJet]

IF your pump is in need of a rebuild, the pump rebuild will be your best performance for the buck. My brother did his pump and picked up 5 mph by closing up the loose tolerances. You may or may not see an improvement, depending on how bad the pump is now.
Doug

[SeaSlut]

How much for the 455; Where is it; How good is it.............

[Jim]

455 olds spun bearing complete with motor mounts,flywheel and adpt water logs water inlet alum valve cvrs, no carb or dist. Jim (818)890-1867 Pacioma Calif