5.7L circulating pump questions

[mr300z87]

Today I started my spring prep to get ready for the summer boating season, one of the items on my list is to replace the circulating pump on the front of my 88 vintage 5.7L (serial no in signature file). I purchased a low hour used OE/Merc/GM pump part # 850399-1 which is listed as the replacement for my older version #17437. The old pump looked to be original Merc/GM, was noisy, leaking and very corroded. My questions is my original pump and the block have and extra hole on one side of the pump. See photos circled in red is the the hole I am referring to in the block.

And here is a photo of the new and old pumps side by side. Again circled in red is the hole, new pump on right, notice the flange has no 3rd hole nor will it cover the hole in the block.

The hole on the block side seem to be blind and I could not blow into it. On the old pump it goes leads into the large water tube. The gaskets are shaped to accommodate this extra hole. My fear is that this pump will not work with my engine and whenI start it water will come shooting out of this hole because the pump does not cover it. If this is not the case then why did GM make the change to the pump housing and or the block? Most likely will not be putting it back together until next weekend so I look forward to opinions on this before hand. Have a great evening and as always any info is greatly appreciated.

 

[mr300z87]

Bump! Anybody have any insight?

 

[alldodge]

Today I started my spring prep to get ready for the summer boating season, one of the items on my list is to replace the circulating pump on the front of my 88 vintage 5.7L (serial no in signature file). I purchased a low hour used OE/Merc/GM pump part # 850399-1 which is listed as the replacement for my older version #17437. The old pump looked to be original Merc/GM, was noisy, leaking and very corroded. My questions is my original pump and the block have and extra hole on one side of the pump. See photos circled in red is the the hole I am referring to in the block.

And here is a photo of the new and old pumps side by side. Again circled in red is the hole, new pump on right, notice the flange has no 3rd hole nor will it cover the hole in the block.

The hole on the block side seem to be blind and I could not blow into it. On the old pump it goes leads into the large water tube. The gaskets are shaped to accommodate this extra hole. My fear is that this pump will not work with my engine and whenI start it water will come shooting out of this hole because the pump does not cover it. If this is not the case then why did GM make the change to the pump housing and or the block? Most likely will not be putting it back together until next weekend so I look forward to opinions on this before hand. Have a great evening and as always any info is greatly appreciated.

I noticed your post when posted but could not speak with authority. Did a lot of looking around and could not find anything which discussed the issue. I would think that if high pressure air will not go through, and the hole is shallow your probably ok. As you say the new pump is listed as a replacement.

 

[alldodge]

Update: just found some pumps which are listed as part number 8503991 which have the three holes. You sure your new pump is the same number?

 

[mr300z87]

Thanks for the reply AD, I have found the same thing. The one I have is an actual Merc part that came off a 2012 350mag with less than 50 hours with a GM casting # on it which I can post tonight when I get home. the aftermarket pumps that cross reference with the 8503991 part number seem to be the ones with the 3 holes. I also did some research last night, looking at auto pumps (no plans to use one) and found that pumps listed for SBC up to 1995 have 3 holes and pumps listed for 1996 and above only have 2. Not sure if the vortec block (1996) was changed. Friday I am going to bolt it on see what happens. Worst case I have a water spaying out of that hole in the block and I replace the pump with the aftermarket pump I have and a couple $$s in gaskets. I will post my results for the next guy.

 

[Fun Times]

I purchased a low hour used OE/Merc/GM pump part # 850399-1

How sure are you that you bought the correct used part number 850399-1?

Did you see it come off of a small block? Typically the big blocks utilize the 2 hole while the small blocks has the 3 hole + 3 hole gaskets....

Are there any numbers on the 2 hole pump itself? Can you post an overall front and back shot of the 2 hole pump? Thinking maybe it's a big block pump.

Here's a big block pump to compare just in case.
http://www.ebay.com/itm/MERCURY-WAT...541-/131283608135?hash=item1e911ce247&vxp=mtr

 

[mr300z87]

Thanks for the reply FT. It is definetly not a BB pump as the ports are the same size as the one I took, off BB ports are larger. I thing the guy I bought it from was trying to use it on a BB because the gaskets that cam with it did not fit. I will post photos and the GM casting # when I get home. Below is a photo of a 1996 and newer SBC automotive pump clearly showing 2 holes. I will get to the bottom of this.

 

[Bondo]

Ayuh,.... Good to know the water pumps changed with the Vortec changes,......

Have to tryin' remember that one too,....

 

[mr300z87]

I guess the big question is will it work. Merc seem to say so since they list the new part # as the replacement pump for my 88 engine. As stated going to bolt it on Friday and see what happens.

 

[mr300z87]

Well I put the casting number 12598183 into google and I get not much, one old eBay post listed as a ski centurion part and it is the same as mine even the cast #. Then another current listing for a pump with the same casting # but it has 3 holes and listed as late model 4.3L that is a different Mercury part # than 8503991 listed for my engine. Now totally confused. Also found that there are 2 different Sierra #listed one for composite timing cover 1 for steel. Could not find good photos of both to compare. Still think I will bolt it up and keep finger crossed.

 

[BRG25]

Why don't you call Mercury Marine and ask them? They were very helpful when I was researching my exhaust manifolds.

920-929-5040

 

[mr300z87]

Life got in the way yesterday so I have not had a chance to install and test the pump. I have done a little more research on this and although I have not been able to find a photos of a 350/5.7L block without the 3 holes I have found out that the pump I have is an original equipment pump which means it was on the Mercruiser engine when it was delivered new. This pump was supplied by GM and I am wondering if by 2012 GM had found the 3 hole not needed and removed it for the casting??? All the Quicksilver/Mercruiser replacement pumps do not carry a GM casting # (as mine does) just like all the other aftermarket pumps which all have 3 holes. Hope to have it installed later today. Have a great day

 

[Fun Times]

Looking around the only pump that I know of that went to a 2 hole is in 2007+ on the 4.3's V6's... I believe they made some changes to the V6's in 07 but not totally sure what it was. The 2 hole starts on the 1A063240 & Up range. http://www.mercruiserparts.com/selec...+ALPHA%2FBRAVO < is dead so now it's, http://www.mercruiserparts.com/bam/subassembly/31507/13808/110

 

[mr300z87]

Success, I installed the pump with 2 holes on the engine yesterday but did not get a chance to run because of the black clouds coming into my area. My friend came over a little while ago and we fired her up on the hose, I figured the worst that could happen is water would be leaking from the 3rd hole in the block. NO water everything is quite and smooth, ran right at operating temp. FT in using the part at the 4.3 link you sent I found a pump on line that has the same GM casting # as the one I used. At lease this solves the mystery of the pump I have. Is there any reason not the run this pump? I was told that the pump came off a 2012 350Mag but I have no was to confirm this.

 

[mr300z87]

One more note that I just thought of, since this is a GM factory warter pump that was delivered on a Merc Engine, that GM started to used the 2 whole pump on the 5.7L/350s and maybe the 5.0s also but they still show the 850399-1 as the replacement. See photo post 7 ^^^^ of a replacement auto water pump with 2 holes for a post 1996 5.7L truck engine ). I know mine is a factory part because of the gloss black Merc finish that is different then the aftermarket units I have seen. Also the 2 plugs were outties (wrench), as opposed the all the replacement pumps I have seen that are innies (1/2 ratchet with no socket). Off to do more maintenance. Have a great rest of Sunday. BTW this is just an opinion.