Calling all Alpha One Gen. 1 water pump experts

Danny Troy

Danny Troy

Member
Oct 8, 2009
861
Candlewood Lake, CT
Boat Info
2003 280 Sundancer
Engines
496MAG w/genset
I thought I'd get the jump on next seasons Spring commissioning things to do, and did a water pump change today. This is the first time I'm doing it on this boat, and actually the first non-outboard impeller I have done.

I wound up with the extra unused parts shown in the photo. One concern is the water tube that slips down into the plastic guide tube. I didn't see any washers or gaskets when I removed it. Are there any gaskets or washers needed here? One of the spare parts is a rubber seal, and I'm wondering if that was supposed to fit on the water tube, coming down from the upper gear case. Also, there is a metal compression pin that I didn't use. Where does that go?

If I have to re-do this job, I'm thinking I'll replace the entire unit. I removed the lower case and the center rubber ring didn't look very good. I bought the minimal kit, without the upper or lower case. Thanks for any advice.....
 
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The bottom 2 gaskets in your pic are for the gear lube drain & fill screws.
 
Thanks, I should have known that. Easy enough to add those two.

Now, anyone for the other pieces, especially the rubber sleeve/gasket???
 
BlewByYou88... Guess you posted at the same time I did, answering EricW. I checked that site and can't seem to find that photo you posted. I have a similar breakdown photo in a Seloc shop manual, but there are slight variences from what I have in my lower unit.
 
I decided to do the job over with a new complete upper and lower pump kit. I'm not 100% sure the lower seal is good, and as far as I could see there's no way to test it. In the future I will do a complete kit replacement. They aren't very expensive when buying online. As a matter of fact I saw Sierra kits for less that what I paid for just the Merc impeller kit.

BTW, anyone know of an easy way to test to see if the drive is in fact in forward gear when bolting up the lower to the upper unit? I read one explanation that says to turn the driveshaft in a counter-clockwise direction, while turning the shift spline in a clockwise direction. If this is correct I would be turning the driveshaft in the opposite direction of normal travel, and the impeller will get going backwards.
 
Thanks for the link. I think I will print it out for future reference.

I see they make no mention of a seal or gasket for the water pickup tube. I guess it's a tight enough fit when the lower unit is reassembled. Also, they mention turning the driveshaft counter-clockwise to get it in forward gear. I think I will put a little lube on the impeller blades to assist in turning in the wrong direction.
 
It's a good idea to lube the impeller blades with some liquid soap anyhow as it will ease the installation of the impeller housing. When turning the PROPELLER shaft you will only have to turn it a little bit to insure the lower unit is in forward gear. After the lower unit is completely assembled and you begin to mate it with the upper you may or may not have to rotate the PROPELLER shaft a little bit more to engage (connect) the upper and lower drive shafts. Don't forget the oil passageway o-ring between the upper and lower (letter B) in the third to last pic in the above mentioned link.
 
Yes, I actually lubed it was spray Fantastic, and it went on without requiring too much effort. I saw one Youtube video where the mechanic put the impeller in the upper portion before putting it on the driveshaft. I believe it was a Gen. 2, which has much longer impeller blades. It's pretty much impossible to do with the shorter Gen. 1 blades.

Any yes, I was sure not to miss that little oil seal.

Too bad I have to do this job all over again, but I should have gone with a full pump set from the get-go. It's been at least a few years since it was done, and I'm sure the lower seal is getting old. I'll take the drive apart and read the part numbers off the existing pump, to be sure I get exactly what I need. Luckily I'm semi-retired and have the time :thumbsup:
 
wish2fish said:
are you sure? I know we don't have scale but those look pretty big in the picture.
Click to expand...

They might appear large because I made the photo large. They are only about 14mm OD, so I'm pretty sure they are for the oil plugs.

It's the two top gaskets that have me stumped. The one on the right might be able to stretch to fit over the pickup tube, where it enters the upper drive. I wasn't aware that that was able to be removed, and I see that the manuals mention a "grommet" that it fits into. I would imagine at times that tube stays attached to the lower drive when removing, but in my case it remained attached to the upper.

I think I can do a head gasket replacement with less fanfare than this :wow:
 
I'm not an expert, but have done mine several times.
Don't forget the to put the little oil seal in place before you put the drive back together. One of those O rings in the kit is for that.
You should also replace the little O ring on the drain plug on the lower half. The old one usually stays in place, so take a pick or something like that and pull it out.
There is no seal for the plastic tube. It just fits in place.
The Gen 1 kits come with a new housing for the impeller.
 
Here is the description of the kit:

Water Impeller Repair Kit Includes new impeller, face plate w/ face plate gaskets, drive key or pin, water tube guide sleeve, O rings and gearlube fill & vent screw seals. Fits Mercury/Mariner 65 hp (4 cylinder) through V-6 outboards with short-vane impellers and fits MerCruiser I/R/MR/Alpha drives (s/n 2495186-0D469858).

looks like it fits multiple drives so that might explain the extra parts.

info from this page
http://www.marineengine.com/newparts/part_details.php?pnum=MER47-89984T+5
 
Yes, that's the exact kit I have. The extra rubber bushing (or grommet), and the extra washer is shown in the photo in the link, just below the two fill plug washers.

JVM225.... yes, I did remember to install the oil seal.

BTW, this Gen. 1 kit does not include the upper housing. That's probably a more expensive kit. I bought my minimal kit locally and wound up paying $51.00! I'll do mail order on all my subsequent impeller jobs.

UPDATE: I contacted Merc and they say the extra parts are for use with a different model outdrive. I believe the kit even works with a few Merc outboards. Anyway, took the drive out again, and pulled down the copper water tube out of the rubber grommet. I forced it into the top of the water pump case and it's a tight fit, so there's no washer needed there. I guess Mercruiser elected to make that a perfect fit, thus not requiring a grommet at that end.

Also, ordered two full Sierra kits, including top and bottom halves of the pump assembly. I'll keep one on hand for the next pump change. Funny, the basic impeller kit from Merc cost $51.00, and the two full Sierra kits delivered was about $70.00.

Update #2: Received the pump kits from www.marinepartssource.com (best price and quick shipping) and they look great. BTW, FWIW they are made in the USA. Appear to be of the same quality as the Merc pump. The upper cases came with new rubber bushings, so I know the copper water tube will be water tight. Funny, after looking more closely on the old pump, there is a rubber bushing in there too. I had thought it was plastic and part of the case, but this time I used my reading glasses and was able to see it was a rubber bushing (or grommet)!
 
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