Alpha one Gen 1 water pump/ impeller issues

Austen2000 · Jul 24, 2013

1987 Chaparral 170xl
3.0 GM
Alpha One Gen 1

Please forgive as this is my first boat and drive to work on. I've been reading posts for a couple days and can't seem to find this answer.

I purchased 18-3217 is that the correct impeller kit?
If so I think there are extra parts I have removed upper water pump housing, impeller, gasket, face plate, gasket and the key. How do I take off the lower pump housing or does it come off? Other wise I have to many seals and gaskets with this kit.
Also is the a gasket for the shift bolt at the front of the lower unit?

I have used this as an example
Alpha One parts / lower gearcase drawing

Thanks :laugh:

ktbarrentine · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

There are extra parts in the kit..... Just replace the ones you pull off. Your manual (the "right" OEM manual) provides the details on how to get your lower pump housing off. (did your kit come with a lower pump housing. or did you buy one separate? If not, then dont mess with it unless your pressure test shows you the seals are leaking.)

Don't understand this question:
"Also is the a gasket for the shift bolt at the front of the lower unit?"

See this thread for the instructions:

http://forums.iboats.com/mercruiser...oblems-after-impeller-replacement-607425.html

And/or this one:

http://forums.iboats.com/mercruiser...cellaneous-mercruiser-information-329915.html

alldodge · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Austen2000 said:
1987 Chaparral 170xl
3.0 GM
Alpha One Gen 1

Please forgive as this is my first boat and drive to work on. I've been reading posts for a couple days and can't seem to find this answer.

I purchased 18-3217 is that the correct impeller kit?
If so I think there are extra parts I have removed upper water pump housing, impeller, gasket, face plate, gasket and the key. How do I take off the lower pump housing or does it come off? Other wise I have to many seals and gaskets with this kit.
Also is the a gasket for the shift bolt at the front of the lower unit?

I have used this as an example
Alpha One parts / lower gearcase drawing

Thanks :laugh:

Your fine, the impeller is the same and your OK. The kit contains different gaskets for the pump differences from MR to gen 1. The lower housing does not come off for an impeller change. See below on how to

http://forums.iboats.com/mercruiser...placing-merc-alpha-style-impeller-387864.html

ktbarrentine · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Austen2000 said:
I've been reading posts for a couple days and can't seem to find this answer.

Not sure how/where you have been searching, but a simple search of this forum for "Alpha impeller replacement" or "alpha impeller instructions" brings up more info than you can read in two days!! Just sayin'

Austen2000 · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

ktbarrentine Thanks I was concerned about the extra parts.

There is a rubber washer over the shift bolt on the lower unit? This is shown in the third picture I posted I did not know if there was a replacement for that it is really worn. But with AllDodge's link (THANKS) there is suppose to be a stainless steel washer over the rubber washer. Which I found in the bottom of the unit all bent up. Guess I need to find a new part number for this.

Does the bottom of the water pump housing even come off on a Alpha one Gen 1? If so help would be appreciated.
I would like to make sure everything looks good while I have the lower unit off and changing the impeller.

Bt Doctur · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

The lower base comes off prying with 2 screwdrivers from each side. Most replace the base instead of replacing seals If those are your pics, your missing the SS washer that goes over the lower splined shaft.

Austen2000 · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Thanks Bt Doctur, I found the washer in the bottom of the lower drive. I had to turn the unit over and it fell out and I know it was not on when I took it off. I will try to pry the lower base off as you said.

Is there a easy way to pressure test the drive?

The boat has been sitting for about 9 years before I got it about a year ago. The engine runs great after I got it to start. Now I am working on the drive , billows, and shift cable. If all checks out then I will redo the interior ( everything is mostly rotten). If not may have to part out what I have. I call her the BEAST at least for now until she runs on the water for me. I'm attaching a pic for everyone to see.

Austen2000 · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Or what size the insert is for the drive to do a pressure test and where to find one? I have a compression gauge to do it.

Thanks

Bondo · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Austen2000 said:
Or what size the insert is for the drive to do a pressure test and where to find one? I have a compression gauge to do it.

Thanks

Ayuh,... Welcome Aboard,... A Cork, or rubber stopper of the right size will work,...

yer compression gauge Won't though,... it can't read low enough,...

Ya only need 10/ 15 psi,...

Austen2000 · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Bond-o. Thanks
So, I guess I can buy a cheap pressure tester from auto parts store. Guess I can use the end of a gear oil pump for the fitting.

Bondo · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Austen2000 said:
Bond-o. Thanks
So, I guess I can buy a cheap pressure tester from auto parts store. Guess I can use the end of a gear oil pump for the fitting.

Ayuh,... That's the Quick, 'n Easy way to get there,...

nola mike · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Do a search for pressure tester. yes, use the fitting from a gear oil pump connected with some clear hose to a valve stem. Pump up with a bike pump and use a standard tire pressure gauge to measure the pressure.

ktbarrentine · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Austen2000 said:
Is there a easy way to pressure test the drive?

View attachment 204981

http://forums.iboats.com/mercruiser...sure-check-prior-post-233546.html#post1573303

Mix up some dish soap and water in a spray bottle and use it to pinpoint any small leaks in the seals (and in your test rig setup). Get up to 15 PSIG and see if it holds for a couple hours.

ktbarrentine · Jul 25, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Austen2000 said:
there is suppose to be a stainless steel washer over the rubber washer. Which I found in the bottom of the unit all bent up. Guess I need to find a new part number for this.

12-31266 for the rubber washer; 12-29395 for the SS washer

Austen2000 · Jul 26, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Thanks ktbarrentine, I will order those washers. I just bought a pressure gauge at Harbor Freight today to make a compression tester.
after I get the drive back together.

Can you buy washers only for the upper and lower drain screws? Or do they just come with the screws. Part #?

I can't wait to get this unit together and fire it up!

ktbarrentine · Jul 28, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Austen2000 said:
Thanks ktbarrentine, I will order those washers. I just bought a pressure gauge at Harbor Freight today to make a compression tester.
after I get the drive back together.

Can you buy washers only for the upper and lower drain screws? Or do they just come with the screws. Part #?

I can't wait to get this unit together and fire it up!

Most impeller kits come with a couple of vent/drain screw washers..... They probably have them at the counter of the boat store. Otherwise, part number is 12-19183. Amazon has them for a buck a piece. I usually try to have a dozen or so laying around.

Austen2000 · Jul 28, 2013

Re: Alpha one Gen 1 water pump/ impeller issues

Thanks just bought 4 extras!!

Alpha one Gen 1 water pump/ impeller issues

Cadet

Attachments

Lieutenant

Moderator

Lieutenant

Cadet

Supreme Mariner

Cadet

Cadet

Moderator

Cadet

Moderator

Vice Admiral

Lieutenant

Lieutenant

Cadet

Lieutenant

Cadet