TOPIC: HELP....Merc 1250 water pump

Hope someone can help. I'm installing a new water pump kit with housings in my 1250 and the new base is identical except for the depth. The book says I need to shim the base where it meets the the shaft bearing but the new plastic base is about an 1/8" shy of the bearing.

I tried to post pics from my phone but apparently tats above my grade.

I hope someone can help. I have no idea what to do.

Thanks
Mark

The ebay item id given is invalid, no result has been sentHi, Mark, you need a 30278A 1 shim kit, which contains .002", .003", .005", and .010" shims. $5.75 retail from Merc.

Here's a few sets on ebay so you'll get an idea of what you're looking for:



If you have an accurate vernier caliper or depth gage you might be able to get a better idea of how many shims you'll need, it'd take 6 of those shim kits if you're actually short by 1/8"!

www.boats.net/parts/detail/merc/M-30278A%201.html

Worst case, you could cut some shim stock to the proper dimensions, but the factory shims would be a lot easier to deal with.

HTH.........ed

Thanks Ed! I get my calipers and measure. In the mean time here are pics of the base. Everything else matches except the depth. Odd.

Hi,
Unfortunately, you have purchased, or received an incorrect base for your Merc 1250. Do note that in addition to the height difference, that the diameter which enters into the gear housing is too large. When changing out for the correct one, the part number of the correct base changes depending on if the original was aluminum or plastic (Mercury had utilized aluminum up until this time frame, but switched to plastic going forward for improved removal, particularly after saltwater usage). Also, if the base is from Sierra, I do not think they offer the correct base for the 1250, and a Mercury brand one must be sourced.

Regards,
Joe
www.fergusonpoolemarine.com
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Mark, the thickness of the lower flange on the old 1250 pump base looks proper, whereas your new base appears odd to me???

Is that an aftermarket base or a Merc replacement part?

I looked up the part at boats.net, and it shows a P/N of 48747A 1.

The picture of the part at marineengine.com looks identical to your old aluminum pump housing, including the size of the water intake hole. The hole in the new one doesn't match.

Maybe just a case of the wrong part, eh?

www.marineengine.com/newparts/part_details.php?pnum=MER46-48747A+1&ptype=&Engine=&Model=

www.boats.net/parts/detail/merc/M-48747A%201.html

www.boats.net/parts/search/Merc2/Mercury/1250/2314956%20THRU%202839368/GEAR%20HOUSING%20ASSEMBLY%2C%20COMPLETE%20%28PAGE%201%29/parts.html

Just a thought, the pump housings for Mercruiser L/U's look very similar, but are not the correct fit for an outboard.

Something else you could do is lay the pump base gasket on the old housing, then on the new housing, and compare the fitment. Also lay the gasket on the gearcase and make sure it fits there, too. The holes should match up, especially the water intake hole in the gearcase, vs. the pump. If not, it won't seal properly or pump correctly.

Another thing you'll note is the slots in the face of the old pump housing; I don't see those in the new one. These grooves are supposed to be there to provide a lubrication path and I wouldn't install a new pump base that didn't have those grooves.

Last thought, the old housing looks like it's still in pretty good condition (at least what I can see), and you could just knock out the old oil seals and install new ones. Priced them at boats.net and they're under $20 plus minimum shipping of $6.95.

Recommend a coating of Permatex No. 3 Aviation-type gasket dressing on an aluminum pump housing, on part with the O-ring, so it'll never salt itself into the gearcase. Not such a big problem with plastic housings but I'll usually use some there, as well.

HTH..........ed

Hi,
After reading Ed's comments and studying the pictures again, the base does appear to be aluminum (I was a little unsure, as a dark gray plastic was one of the colors that plastic bases were made from). Unless there is damage somewhere the pictures do not show, then new oil seals would be a good solution. However, if a new base is utilized, the replacement for an aluminum one is a plastic one, but it is a different part number than given for the plastic original ones (the website shown does not show this change, only stating that the aluminum one is obsolete).
Also if the original water pump housing was aluminum and a plastic one is being used to replace it, then the lock washers and standard nuts should be replaced with nylon insert lock nuts as the factory did when plastic housings were fitted in production. This is important, as the nuts used with the plastic housings cannot be torqued as high without deforming the housings, and the lock washers and nuts may could come loose as a result.

Regards,
Joe
www.fergusonpoolemarine.com
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Thanks for the replies guys.

I got the kit at West Marine and it is a Quicksilver. I went back on the Old Mercs site to look at the pump kits again and noticed that although the picture shows pump base, the text says does not include the base. So it sounds like that's the kit I got, except the base wasn't removed.

I googled the base part number and an Ebay seller came up and he has them in stock and he's only about 45 min from me...yay! So I have that coming and I'll mate it with the new plastic one.

Thanks for telling me about the nuts/washers. I would have reused them. Also good to know that the seals are available for the base.

Thanks again,
Mark

One more thing I forgot to mention. The plastic upper housing/cover is identical to my old aluminum one except there is NO shaft seal. The housing came assembled with the water tube seals and the SS insert installed, but NO shaft seal. Is this a change? or do I have the wrong part?

Thanks,
Mark

Mark
Later models don't use the upper seal That top will work just fine.

Whew...thanks Tim!