Impeller replacement instructions / Mercruiser - Pre Alpha(?)

[Jim Robbins]

I have looked and could not access -** (How To: Replacing Merc Alpha style impeller
http://forums.iboats.com/showthread.php?t=387864 You are trying to access a page that is no longer valid or does not exist.)**

I have a 140 H.P. Mercruiser S/N 3129102 and Stern Drive S/N 2073371 (1970 - 73(?) I have been told a Pre Alpha (?)
I have a new Impeller kit and I need step by step instructions for replacing. I would bet that some of you could do this blindfolded.
Thanks

 

[Don S]

Re: Impeller replacement instructions / Mercruiser - Pre Alpha(?)

You are trying to access a page that is no longer valid or does not exist.)**

The forums are partially down for maintenance, see the yellow bar note above your post.
I went ahead and uploaded it to 4shared so you can download it until the forums get fixed.
That file is for a newer model, but basically the same. Same look about it.
http://www.4shared.com/office/8wC3RD9w/Mercruiser_Alpha_Impeller_Repl.html?

 

[achris]

Re: Impeller replacement instructions / Mercruiser - Pre Alpha(?)

II have a 140 H.P. Mercruiser S/N 3129102 and Stern Drive S/N 2073371 (1970 - 73(?) I have been told a Pre Alpha (?)
I have a new Impeller kit and I need step by step instructions for replacing. I would bet that some of you could do this blindfolded.
Thanks

You have an MC-1 drive. That it is 'before an Alpha One' is correct, but there is no drive called a 'pre-Alpha'.

The genuine manual for the job is -> http://www.4shared.com/document/ozc1_97A/Service_Manual_01.html

It's not a difficult job, just pay attention to detail. Look for slight melting of the impeller housing, and grooving on the base plate. All gasket surfaces need to be CLEAN, and put the gaskets on dry, or with a SMALL amount of grease. Also have a look at the water pocket cover in the bottom of the top box... Make sure it's in good condition. And when you put the drive back together, DON'T put the 'O' ring in the groove on the top of the drive shaft, toss it in the trash can....

Chris.........

 

[Jim Robbins]

Re: Impeller replacement instructions / Mercruiser - Pre Alpha(?)

Thanks Don S. & Achris, Chris why do you say "DON'T put the 'O' ring in the groove on the top of the drive shaft, toss it in the trash can...." ?

 

[achris]

Re: Impeller replacement instructions / Mercruiser - Pre Alpha(?)

Thanks Don S. & Achris, Chris why do you say "DON'T put the 'O' ring in the groove on the top of the drive shaft, toss it in the trash can...." ?

If you put that 'O' ring on, then as you slide the shaft up through the seal in the bottom of the top box, it will snag and hold the seal open. Checked it many times myself. Happens 99 times out of 100. If you were to buy a new drive-shaft for that drive, it would have no groove in it...

 

[ktbarrentine]

Re: Impeller replacement instructions / Mercruiser - Pre Alpha(?)

Hmmm... I'll have to follow that advice next time. I recently replaced my impeller, put the o-ring on the shaft (per the service manual, and lubed it real good), bolted it all back together and had a great pressure test and the drive is running good (checked the oil after each time on the lake). I guess I must be the 1 in 100. Did they put out a tech bulletin on this?

 

[achris]

Re: Impeller replacement instructions / Mercruiser - Pre Alpha(?)

Hmmm... I'll have to follow that advice next time. I recently replaced my impeller, put the o-ring on the shaft (per the service manual, and lubed it real good), bolted it all back together and had a great pressure test and the drive is running good (checked the oil after each time on the lake). I guess I must be the 1 in 100. Did they put out a tech bulletin on this?

The seal that the 'O' ring holds open is the lower of the 2 in the bottom of the top box. If it's open it will not show on a pressure test. It's there to keep water out of the splines. (The seal above that keeps oil in the box, and is the one the pressure comes up against during a pressure test). The first you know that there's a problem is when the splines in the drive shaft (the one in the top box) rust out and you don't got drive to the prop... :redface: To see the problem you have to have the drive off and supported while turning the yoke and watch the top of the drive shaft (the one from the lower box) in through the exhaust port..... What you see is the shaft turning and a bit of the 'O' ring poking down below the seal. That is where water can get in....

I an pretty sure a bulletin was issued, but I have searched pretty thoroughly and can't find it... Anyway, they superseded the shaft with the groove to one without a groove...

Chris.......

 

[ktbarrentine]

Re: Impeller replacement instructions / Mercruiser - Pre Alpha(?)

Thanks Chris! I will pull my drive soon and let you know what I find. I love learning these things. These forums have saved my bacon on more than one occasion. Hopefully your sage wisdom on this will keep me (and others!) out of future trouble.

 

[ktbarrentine]

Re: Impeller replacement instructions / Mercruiser - Pre Alpha(?)

Pulled my drive today and did a detailed look-see at the shaft seal through the exhaust port. Rotated the shaft 360 degrees, no evidence of o-ring extrusion. Everything looks good. I'll leave it as is for now, but will omit the o-ring on my next impeller change.

 

[achris]

Re: Impeller replacement instructions / Mercruiser - Pre Alpha(?)

Sometimes the 'O' ring will slide on the shaft, get a little dental mirror and have a look around the back...

 

[ktbarrentine]

Re: Impeller replacement instructions / Mercruiser - Pre Alpha(?)

My detailed 360 used an inspection mirror and a 500W shoplight. I really think I had enough 2-4-c on there to slip it past the goalie when I put it together last time. Time will tell and I will see what the o-ring really looks like next time I split the drive. Interesting though...this drive is new to me by a few months. When I split the drive to replace the impeller after purchase, I saw that the o-ring had stayed up inside the upper shaft spline and I had to go fetch it. It was in good shape and didn't look like it had been trapped in the seal. Anyways, good to know I don't have to worry about installing it anymore.