mercruiser 898 lower unit

[boatmanwayne]

I have an 898 lower unit case that is broken and trying to swap internals to another case, but after installing new lower needle roller bearing and inserting driveshaft I still have clearance of the upper tapered bearing even after dropping in .040" of shims, Is there a difference in case dimensions, the newer case is probably a newer make. I have part # of old=1623-5412-s2, part # of newer case is 1623-8950 S, I was wondering if anyone has a reference for the part numbers.<br /> Thanks for any Info, Boatmanwayne

 

[johnkc]

Re: mercruiser 898 lower unit

wayne ,not sure of your question ,can you explain the problem with more detail.

 

[boatmanwayne]

Re: mercruiser 898 lower unit

Johnkc, my problem is that when I install the driveshaft and pinion gear the tapered roller bearing at the top of the driveshaft is not tight in the bearing race, even though I put in a whole shim package of shims of which I know I should'nt need them all.<br />There must be some difference in the cases, but I don't know if the two cases are compatible

 

[johnkc]

Re: mercruiser 898 lower unit

wayne, it is not going to be tight,there is a lot of up &down play .you need shimming tools and a manual to do this .you can't just switch the guts and expect the unit to live .good luck .

 

[boatmanwayne]

Re: mercruiser 898 lower unit

John, I realize there is going to be some free play before shimming, I have the shimming tools and manual but the specs say nothing of this much free play, this is why I think I may have the wrong case.<br />Thanks for your comments. <br />Perhaps someone with references to part numbers will see this and be able to advise me, thanks again. Wayne

 

[johnkc]

Re: mercruiser 898 lower unit

the free play will be there even when properly shimmed .the preload pin in the top end of the drive shaft is what keeps the upper driveshaft bearing in its race when the drive is fully assembled

 

[boatmanwayne]

Re: mercruiser 898 lower unit

Johnkc, okay, now I think I have it, I never thought about what really snugs the shaft down after setting pinion gear height. Makes sense now, thanks again,<br /> Wayne

 

[johnkc]

Re: mercruiser 898 lower unit

 

[johnkc]

Re: mercruiser 898 lower unit

wayne the 5412 case did not come up but the 8950 came up as a 8951. some times the numbers on the hsgs.aren't able to be tracked so you need to just compare side by side.