I need a new circulating pump for my 502MPI and I see these bi-directional pumps as alternates. Will the flow of the bi-directional pumps be the same as a directional pump? Is there any reason to avoid the bi-directional pumps?
TIA

buy a new mercury pump,problem solved.

The Merc pump is made by Sierra Marine aftermarket parts - it is made in the Asian market and Sierra owns the tooling.

Yes Sierra makes the water circ pump for Mercruiser. It is not the best pump in the world either. Is it not bad either but they have had a few problems with them on the longevity side. I have one in now, a 3 year old boat and the bearing went out in it.( Mercruiser ) Boat has less than 100 hours.

Also in 2012 Merc used a GM water circ pump that the internal brass impeller would crack in very short order. This is one of the reason they went with Sierra for the past 3 or 4 years.

There is a USA company that makes marine water circ pumps for Volvo Penta and for Mercruiser reman engines only out of Missouri and now Indmar uses this same company for all their water circ pumps.

These cast pumps to date are the best pumps going. if you can wait out for about 3 to 4 weeks I should have plenty in stock at very good prices - Again these are USA water circ pumps.

Most Marine specific water circ pumps are bi directional. It has to do with the position of the blades on the impeller - they are straight direction not angled like what auto use

Here is an image of a marine 4 banger water circ pump and the backside of the brass impeller, ( the back SS cover has been removed for a display ) see how the blades are straight (they are facing forward hard to see ) - that means its a bi directional pump,

Reason is because marine engines have reverse rotation so by having a bi directional pump it will work for both right hand and left hand rotation marine engines.

Alot of ford Inboards were reverse rotation engines and so were GM / Mercs. The image is the only one I can find at the moment -

http://i.ebayimg.com/images/i/141197...-1/s-l1000.jpg

That is more details I haven't run across so thanks for the input. I could possibly wait. I'm not headed out since I'm working on the trailer too.
Let me know the details when you get them in.

the reason for post#2 was to steer the op from bying a automotive pump.

OK I got you. Not interested in the auto stuff but looking to put a finer point on my marine knowledge.

Is this bidirectional design used on all the BBC type blocks like 330hp, 415hp, 500hp, 525hp, 600hp etc?
I know "flow" is affected by impeller shape and placement and wondered if this is different based on engine power for cooling needs or if the pump is pretty much the same while coolers etc change for power levels.
Can you all school me on this part?

Bi Directional pumps are fine, without closed cooling you need to run a marine pump as the auto ones rust bad quick without antifreeze.