Replace Guts

[manykids]

Sad news to report. The guy who winterized my boat did not check the outdrive. It has a nice crack in it. I have purchased a replacement outdrive (top and bottom). The replacement came off a 6 cyl. boat, but mine is a 305, so we plan to pull the guts out of mine to go in the shell of the replacement. What do I need to consider on the lower unit besides the water pump / impeller and the associated seals? It is a 1979 Cobalt w/ a Mercruiser.

 

[tommays]

Re: Replace Guts

what happened ? did you have the drive tilted up and crack the lower case

If that was the only problem the upper would still be good and it is were the gear ratio is done

it will to bolt up to a different lower of the same age BUT they share oil so any other problems with the upper or lower would dammage both

your not just gonna swap parts

EVERY case is different and and all the parts are shimed for bearing and gear fit.

It requires a lot of Merc tools and many of the steps require hands on training to really understand how to do it

http://www.boatfix.com/merc/Servmanl/6/6covr3.pdf



Tommays

 

[manykids]

Re: Replace Guts

Yes, it was up for the winter. I did not know this would be an issue.

If the replacement case is the same, why will the insides not swap out? What exactly should I do? I don't want to mess the whole thing up. I was planning on just swapping out the lower case with my original guts.

 

[Don S]

Re: Replace Guts

The cases are castings and all castings vary and the machining may be slightly different, maybe only a few thousandts of an inch, but enough that the parts can't be removed from one housing and put in another without shimming for bearing preload and gear heights.

 

[manykids]

Re: Replace Guts

You all are not filling me with a lot of hope. Can the replacement lower unit be used if properly aligned?

 

[Don S]

Re: Replace Guts

If you bought the right housing, yes your parts can be put in it. But they will have to be shimmed properly. This takes special tools for setting gear heights and preloads.
Look at that link Tommays posted and go to section 3B and see what all is required.

 

[tommays]

Re: Replace Guts

Like i said if your OLD upper is good it can be bolted to the NEW to YOU lower if it is good and the same vintage

The final gear ratio is done in the upper BOX all the lower units have the same gears


This would keep the gear ratio you need and be and easy way to do the repiar


Tommays

 

[manykids]

Re: Replace Guts

I have made an appointment with a marine mechanic. The price will actually not be that bad IF there are no other problems. As a bonus, he will check all the upper for problems while it is torn down. At least it will ease concerns over the outdrive life span. Thanks for all your help.