1979 Mercruiser 120 water pump impeller replacement

[chelms24]

Hello all,
I am a fairly new boat owner, the boat was given to me as a project boat a few years ago and I have been fixing it up here and there as time and money allow. boat is a 1979 Starliner with a 120 Mercruiser 4 cylinder motor and 120 pre-alpha stern drive. the motor runs good so far (just got it wet for the first time earlier this year).

I will be attempting a water pump / impeller replacement for the first time this weekend on the stern drive unit and have a couple of questions.

1. Is there a seal that goes around where the upper and lower units come together? or is it only sealed where the gear lube flows between them? should I use any type of sealing compound around where the two meet?

2. I have the sierra water pump kit (part# 18-3317) two quarts of gear lube, gear lube pump, and a tube of marine grade grease, is there anything else i will need for this project besides tools? the service manual mentions "perfect seal" a few times but i am not sure what that is. is it like a gasket sealer? I do have an automotive grade spray on gasket sealer would this work?

3. Do i need to have it in forward gear before separating the upper and lower units? the service manual only mentions putting it in forward gear when putting them back together but I have read conflicting reports here on the forums.

Sorry for all of the question but the service manual is a little vague in some areas.
and I wanna make sure i do it right the first time.

Thanks for your help.

-Chris

 

[chelms24]

Re: 1979 Mercruiser 120 water pump impeller replacement

Would it be a good idea to use some RTV between the upper and lower unit when I reassemble?

 

[ziggy]

Re: 1979 Mercruiser 120 water pump impeller replacement

1. no seal between the upper and lower EXCEPT the one quad ring seal the seals the gear lub passage between the upper and lower. no sealing compound
2. gaskets go together dry. no adheisive.
3. if your just dropping the lower, no, it don't have to be in fwd. however you'll find it very helpful to put everything in fwd. when reassembling, or, ya run the risk of not assembling it proper. best is to just get in the habit of when ya drop the lower, or pull the drive. just put it in fwd.
to keep in in fwd. during reassembly. consider using a bungee to load the prop ccw. any cw motion of the prop during reassembly takes the lower out of fwd gear and leaves it in neu.

ya may also consider pulling the whole drive. theres pm to do when ya pull the whole drive. ie, gimble brg. check, lub ujoints, check alignment etc. also. putting the lower back while the upper is still on the boat is doable. but painful generally. putting the lower and upper together on the bench is a one man job. much much easier to do. then put the drive back. to remove the whole drive. it's gotta be in fwd.

if yer working on yer boat. ya need to get a service manual. probably #3 and #4. mercruiser manuals.. sorry no link. but still look into getting them. indispensable tool imho..


no rtv...

 

[Bt Doctur]

Re: 1979 Mercruiser 120 water pump impeller replacement

Who`s manual are you using?

 

[chelms24]

Re: 1979 Mercruiser 120 water pump impeller replacement

I have the Mercruiser service manuals #3 and #4 but the pictures really suck and they don't seem to be too detailed on some of the procedures.

Thanks for the Info ziggy I think I will just pull the whole drive.

I am assuming that the drive should be trimmed all the way down before removal, but it doesn't mention this in the manual #4 sect 3A-3.

Also, the rubber bushings on the power trim cylinders look pretty pretty cracked do these need to be pressed in by a shop or could i put them in myself? would anyone happen to have a part number for these bushings? I searched this site and found multiple different ones. I think they might be These but i'm not sure

The good news is I drained the gear lube earlier and there wasn't a hint of water

 

[Bt Doctur]

Re: 1979 Mercruiser 120 water pump impeller replacement

Those bushings are for the later drives, not the early ones like yours.They are installed by hand.
Drive should be shifted into foward gear first,fully lowered for removal ,remove rams, 6 mounting nuts, pull straight back.sometimes you need to raise the drive a bit and let it drop back down to break the gasket seal.Just be careful it dosent come off by itself.
look in here for some better pics. http://www.boatfix.com/merc/Servmanl/6/6covr3.pdf

 

[chelms24]

Re: 1979 Mercruiser 120 water pump impeller replacement

Is the outdrive housing gasket reusable or will I need to order a replacement? it looks like this is the one I would need

Are these the right trim cylinder bushings? My drive serial number is 5324965

Thanks again for all of the help

 

[Eric 3.7LX Alpha 1]

Re: 1979 Mercruiser 120 water pump impeller replacement

Here are a couple of videos to watch in addition to the manual info-

Separating the drive:
http://www.youtube.com/watch?v=kfpasFN_g8w&feature=mfu_in_order&list=UL

Water pump video:
http://www.youtube.com/watch?v=0QC6_j2_wmA

 

[ziggy]

Re: 1979 Mercruiser 120 water pump impeller replacement

I have the Mercruiser service manuals #3 and #4 but the pictures really suck and they don't seem to be too detailed on some of the procedures.

thems the sm to use. good job. but ya gotta read them close. i've found that there is something ya gotta do in near every sentence that is written. when i have a project to undertake. i read up on it multipule times. try to understand best i can prior to diving in and doing the deed. don't read into what you read anything other than what is printed. if mercruiser want's ya to use some kinda goop, it will say what kinda goop to use.

I think I will just pull the whole drive.

imho, that's great. ya might wanna go here. http://forums.iboats.com/showthread.php?t=288430 look at #19. build yourself some form of drive stand. this will really help when R&Ring the drive. which when ya have a stand you can do by your self. fwiw. get the alignment bar now too. if your gonna be pulling the drive. ya should check alignment ea. time. easy to do when ya got the tool. i procrastinated about getting one. i shouldn't have. for drive work, it should be one of the first tools ya get.

Also, the rubber bushings on the power trim cylinders look pretty pretty cracked do these need to be pressed in by a shop or could i put them in myself? would anyone happen to have a part number for these bushings? I searched this site and found multiple different ones. I think they might be These but i'm not sure

those look like the right type to me. ask your dealer about what he has for you. he'll get the right ones too. http://www.mercruiserparts.com/Show...CYLINDERS+AND+HYDRAULIC+HOSES+(EXTERNAL+LINE) i think item #15 is right too. but don't hold me to that. the pic of that part don't look right. but, use a site like bam (mercrusierparts.com)_that has oem part numbers for ya, then ya can cross referance to aftermarket parts if you want.

 

[chelms24]

Re: 1979 Mercruiser 120 water pump impeller replacement

okay, so I got the drive off and separated the upper and lower, I reached up into the upper to make sure that the o-ring on the drive shaft didn't get stuck and I found this little plastic gem (See image)

Any ideas what this is?

 

[dozerII]

Re: 1979 Mercruiser 120 water pump impeller replacement

okay, so I got the drive off and separated the upper and lower, I reached up into the upper to make sure that the o-ring on the drive shaft didn't get stuck and I found this little plastic gem (See image)

Any ideas what this is?

That little jem is half of your exhaust shutter. They tend to burn,melt, break off in the center and fall down to where you found it. They are mounted in the exhaust tube under the riser bellows, and can be a !@# to change. I just did mine this spring. The photo shows what is left of the shaft on mine.
Glen

 

[Bondo]

Re: 1979 Mercruiser 120 water pump impeller replacement

Any ideas what this is?

Ayuh,... That's the remnants of the exhaust shutters...