Another RWP question

Grant,
I don't understand what's wrong with the RWP set up now and it needing to suck? As long as the suction head isn't exceeded, a flex impeller pump is pretty simple. What design of electric pump are you thinking of? Centrifugal?

Yes see the link. It can be done. This applies more to off-shore fishing boat that are equipped with a raw water wash down system. Same theory. In concept an electric raw water pump would free up some engine horsepower. Many modern performance cars have electric water circulation pumps.

www.thehulltruth.com/boating-forum/145799-connect-raw-water-wash-down-engine-flush-emergency.html#b

Not much wrong with the way it is now. But as in high performance cars, the electric pump would provide more hp at the prop (or wheels in the case of cars.) I think it would also "clean up" the belt area, etc.
I can't suggest a "kind" of pump.
Its speed would not have to be altered, methinks. It would be sized to always provide more than needed at the engine's thermostat, with excess sent to exhaust manifolds.
I'm not arguing FOR the idea. Just thinking aloud.
One of my cars has gravity fed fuel. Then the car mfgs. used mechanical pumps ABOVE the fuel level. A bad system that was used for many years -- while our car-makers added tail fins(!). My boats have mechanical fuel pumps, below the fuel level. My car current has an electric fuel pump -- below the fuel level. Maybe there were some good reasons for these changes. Just thinkin'.

Many current cars have a way to call for help too,a coincidence?

For your reading pleasure and enlightenment.


www.motor.com/magazine/pdfs/112009_07.pdf

Your math is sort of right - at least at low rpm's approaching zero. What your calculation lacks is the change in power input required to drive a mechanical water pump at varying RPM's. The power required increases as a cubic function of the engine speed; whereas, the power input required for an electric pump is relatively constant assuming fluid viscosity and resistance remains constant. At higher rpm's the ewp's become more efficient than the mechanical pump. I'm not selling electric water pump's...... but, it also seems like there are a whole lot of people selling and spending time working on the mechanical pumps too. I like to see technology change and improve and I believe this is an area of opportunity.

Both, but the greatest opportunity I think is with raw water pump improvement. There has not been much change in the technology in the last 45-50 years. We are still running the same exact type/models of rwp's that we had in the 70's when I was in high school. If we don't think there is anything wrong with the technology, just consider for a moment how many questions and discussion points arise on this forum (and others) about pump impeller failure, bearing seizure, leaking, and the resultant heat exchanger fouling just prior to engine and/or head damage from overheating.

Can't remember the last time I packed a spare part for an automobile trip... but, we sure carry an extra rwp when we go off-shore to chase fish in the Gulf. We are currently a building a new engine for my 86/87 Fish. I went through my spare parts inventory to see if there was anything left from when I sold my Shamrock we could use - Shammy's used a crank mounted Sherwood P105. Was trying to see if there was enough room to mount it on the 351 - there is not. I have both an P-105 impeller and a complete pump in my tool shed. Where we fish we are always one sandbar, mud flat or soft bottom at low tide away from needing one or the other.

Pardon me while I get down off my soap box long enough to call Skidim for a belt driven Sherwood............and a spare impeller.

My G21 pump is plugging along with somewhere north of 1600 hours. I'd say those are pretty reliable pieces of equipment.

Gary S wrote: Later HM's added a circulation pump so they must have realized they had a problem.

I have mentioned it before that there really wasn't a problem with running a RWP only on the early V8's 6's or 4's. It was a matter of history more than anything. When the early industrial blocks were marinized, they knew a pump with some suction life was needed due to most engines sitting above the water line so the RWP was added. They didn't want to be redundant plus back in those days T stat's were not even used. Then they found it was actually less expensive to purchase the long block with the circ pump rather than making up the block off plate for where the circ pump would have been in a non marine application.

Before the advent of decent rubbers, the early RWP's were gear pumps. They did need to be primed to close off the tight fit (.0005" when new) between the gears and hosing. Screw in grease cups served the purpose. Before starting you would screw the cups in which would pack the pump with grease sealing the clearances. After years of usage, the clearance due to wear became to great for the grease to seal and the pump would need a rebuild or replacement. Along came the flex impeller pump.

Yes, I too believe the present day RWP is pretty simple and proven to be reliable. An electric in my opinion just adds complexity and the need to be sized for the max heat removal during max RPM's. This means an electric needs to deliver the same GPM at idle as WOT adding inefficiency. The crank or belt driven RWP delivers the needed water at varying loads since they run at the varying RPM's of the engine.

GMacLaren wrote: Speaking of gear pumps, this from my junk drawer:

Pull the cap and get a feeler gauge between the gears and between them and the housing. Anything past .0005" and it's bad. Also get the dial indicator out and measure for any axial play in both shafts. It maybe junk! Where did it come from?