mercruser 140 drive shaft sheared

[suzukisam]

I just recently accuired a 1979 seasprite with a gm 4 cyl and a 140 mercruiser outdrive. the boat is nice and runs like a top. a fresh blue stripe on the side to cover the old one and some new seats and it will be like a new boat! however in the process of going through the boat I found the prop won't turn(with the help of the engine). it will turn by hand and is smooth and free, but it would not move a milimeter in gear. so I went through the checking process and ended up pulling the lower unit off and lo and behold the drive shaft came off at the top. where the o-ring is just below the splines it has sheared, cleanly. I have never done any boat mechanics before, but build plenty of car engines and atv engines. mechanics are not beyond me.
how do I determine the correct shaft to buy (alpha, pre-alpha, I, II, ect..) I know mine has the o-ring groove and I think it has that "pre-load pin"??? help! I'm going to do the water pump while it's apart anything else I need to know while she's apart? I wanna do it right the first time

ok I just looked up the sn 5162665 1.98R is also on it

 

[meesh]

Re: mercruser 140 drive shaft sheared

Probably cheaper in the long run to get a new lower or a complete unit from Stern Drive Engineering.

 

[suzukisam]

Re: mercruser 140 drive shaft sheared

I can get a drive shaft for under $200 a lower unit is $700 how is that going to be cheaper? I'm not being smart, I'm just asking.. also what I didn't mention is that the whole lower unit was rebuilt two years ago. I'm not sure how this happened, but from the looks of teh prop I'm going to guess a sand bar..

a water pump kit is like 30.00 I'm thinking under $300, and if I dig around probably under 200, I can have her like new again! anyway any input is helpful.. also what do you guys hink of a used shaft? if I find one on feebay or a salvage? I'm not big on used parts but if it's clean I would consider?

 

[chiefalen]

Re: mercruser 140 drive shaft sheared

Hello and welcome aboard !

I don't think anyone was being smart with you. Taking apart the lower unit and rebuilding it, requires special tools. And they ain't cheap.

Also i am willing to bet it just ain't the shaft that gone in the unit.

I would recommend you take it apart and then post a picture of all the damage done in the unit we can go from there.

Good luck !

 

[suzukisam]

Re: mercruser 140 drive shaft sheared

I will try to get pics up but it will probably be the weekend. this unit was recently rebuilt and I'm wondering if the drive shaft wasn't done.. see my friend had it and his brother hit a sand bar. It tore the prop up and it got a complete rebuild from the insurance company. I'm just wondering if the drive shaft was compromised and the mechanics missed it and it got reassembled? I'm not sure.. I'm supposed to be getting another outdrive for free in a couple weeks and my intent is to use the best stuff out of both with a new drive shaft and water pump and put it together.. I've inspected the gears and seals and all seams to be well.. I'm not a boat mechanic but I know a good gear from a bad and these are nice! prop bearings seem to be good and so does the gear box it's just this darn drive shaft is cracked clean in half.. all the U-joints are nice, very smooth, no slop.. if you guys will give me a list of things to check.. I would like to know common failure points of the outdrives.. i know the impeller is good to change.. any oil seals that don't look fresh...

as far as the tools I got that covered my grandpa bought the same boat new and was a machinist and made what wasn't readily available, and purchased the rest..

I know no one was being smart.. I just didn't want to give the impression I was

 

[chiefalen]

Re: mercruser 140 drive shaft sheared

Seems like you have it covered need a manual, go to the top of the forum page " Adults only " And pull the manual you need and d/l it.

It's free and a valuable resource courtesy of Don s.

 

[Bondo]

Re: mercruser 140 drive shaft sheared

t's just this darn drive shaft is cracked clean in half..

Ayuh,...

That's common enough that Merc got rid of that groove,+ it's O-ring in later models...

Grab a copy of the Manual suggested by Cheif,...
It'll help with the assembley,+ tolerances...

 

[suzukisam]

Re: mercruser 140 drive shaft sheared

ok got the manuals and most of what i need.. now can you guys tell me this... I'm finding a lot of drive shafts that claim to fit my serial numbers... and look the part. but they just don't have that o ring.. can I replace without it? if the drive shaft fits my replacement part number? I'd love not to have it if they are a problem anyway?

 

[JustJason]

Re: mercruser 140 drive shaft sheared

I can get a drive shaft for under $200 a lower unit is $700 how is that going to be cheaper?

Because you need a thousand bucks in tools to do the shaft correctly. You need a gear height gauge to set the pinion. you also need a shift shaft tool, a bearing carrier retainer tool, a spline socket for the driveshaft, a dial indicator, a micrometer or good veneers, a dial indicating torque wrench to set the bearings, a pinion nut wrench... etc.
If you just want to swap the shaft out by guessing... best of luck and I look forward from hearing from ya in a few months.

BTW.... the driveshaft usually shears when there is a high speed hit.

If your a diy'r.... i agree with Meesh.... an SEI drive will be the way to go.

 

[suzukisam]

Re: mercruser 140 drive shaft sheared

well this is all the info I'm trying to collect.. I've been reading the manual and it seems straight forward.. I have a bearing press and most of the other tools and I belive my grandfather and uncle have the rest.. I don't intend to guess but this is an older boat and I just want to put it back so that it is reliable and least cost over all.. I just found a new drive shaft for 100.00 if I have to spend a little on a few things I'm still ahead.. I'm looking for advice on how to get the job done properly.. when I collect all the info I will decide what is in my realm of ability... again machining and engines are very familiar to me.. this is not my first rodeo.. just my first mercruiser!!

 

[chiefalen]

Re: mercruser 140 drive shaft sheared

Go for it, not everyone was born with a 100 drives rebuilt under their belt as someone who tried to discourage you posted in this thread.

 

[suzukisam]

Re: mercruser 140 drive shaft sheared

Chief can you tell me I have the pdf manual I downloaded for the tear down, and rebuild. it'snot really detailed, is there anything else I need to know? I've been reading up on the shimming process? any tips would be great. a couple of the tools the previous guy listed in his post I did not see listed in the manual?

 

[Big Boat Bay Buster]

Re: mercruser 140 drive shaft sheared

I'm confused?? You keep asking for tips on the drive rebuild, yet you say you have mechanical experience. I would equate this repair to putting the rear end differential back together in a car. Check the gears for any missing , scored or chipped teeth. Check the bearings--discoloration, damaged rollers---make sure the race is nice and smooth. You need to get the pre-load on the bearings just right and the clearance between the gears needs to be on the money. Screw this up and I guarantee the drive WILL blow up when you are out on the water.All this is explained in detail on both the service manual and the Clymers as well.
When I needed a new Alpha drive, I found one on Craigs list for $500. It was a complete drive purchased new from Mercruiser and used for 2 seasons. Alphas are plentiful--Good deals are out there!!
If you do rebuild it yourself, take pictures. If you are successful-post the pics. I would love to see how its done.
Good luck
Chris

 

[chiefalen]

Re: mercruser 140 drive shaft sheared

This has been discussed many, many times on this forum.

All i can attest to is what i have done, with the aide of other mechanics, with vast knowledge at my side.

What tools we didn't have we made, such as a spanner wrench and such.

We had a vice and between the 3 core guys working on the gen 2 drive first drive we worked on we followed the seloc manual. And we pooled our tools.

The merc drives we rebuilt are still going strong and it's 3 years latter. For the first one.

I did many omc drives but it's a different dog the stringer drives.

I also did outboard drives different again.

The original poster says he has 2 mentors that are machinest , no reason it can't be done.

 

[JustJason]

Re: mercruser 140 drive shaft sheared

your not going to be making a gear height tool at home.... believe me. And the only place your going to find the extra long feeler gauges is through snap on.

 

[chiefalen]

Re: mercruser 140 drive shaft sheared

Again how do you know what his machinest grandfather and uncle have access to ??

They may have more stuff then you.

I know you ain't asking what i have access to.

 

[ziggy]

Re: mercruser 140 drive shaft sheared

i aint the pro here. i've also not ever had a lower apart. so ya can take what i have to say with a grain of salt. but here's what i've noted..

I'm going to do the water pump while it's apart anything else I need to know while she's apart?

good that yer gonna do the water pump, it's yearly pm. and i don't beleive you'll know what else needs to be serviced till you have it in pieces in front of you...

a water pump kit is like 30.00

$40 w/o a pump housing, $50 with a pump housing. i just bought one a day or two ago. oem mercruiser...

also what do you guys hink of a used shaft?

i'd check it careful. oil seal wear, splines... new would be better..

I've inspected the gears and seals and all seams to be well..

I know a good gear from a bad and these are nice! prop bearings seem to be good and so does the gear box

how do you know this. you need it tore apart to see....

if you guys will give me a list of things to check..

this will be noted in the oem service manual as to what to look for...

but they just don't have that o ring.. can I replace without it?

from what i've read. yes. and i've read it more than once. mercruiser did away with this groove, apperantly this oring is not nessesary. and i'm convinced it's not by reading it many times on this forum... all this oring does is cause grief... proof would be that the oem replacement will have no oring groove.

Chief can you tell me I have the pdf manual I downloaded for the tear down, and rebuild. it'snot really detailed,

the oem serivce manual is most detailed. you need to read it sentence by sentence. they pack a lot of info into a very short space.. while i've only worked on a upper. i just can't tell ya how many times i read the s/m over. everytime gaining more insight. then came to iboats and asked further about what i didn't understand..

If you do rebuild it yourself, take pictures. If you are successful-post the pics. I would love to see how its done.

agreed. that would be most helpful for many other users. when i worked on the upper. i had many pics i posted up about the condition of my parts..

lastly. myself. if i could afford them. i'd use oem mercuruser parts. remember. aftermarket is a copy of oem. how sure can you be that it's a proper copy. i've seen glm parts that aint to close, like don't even work... so be carefull about aftermarket imho. good luck on your adventure..

 

[chiefalen]

Re: mercruser 140 drive shaft sheared

That Ziggy he knows how to say it better then i ever could. ^5

 

[suzukisam]

Re: mercruser 140 drive shaft sheared

thanks chief and ziggy! I've noted all you have to say and I am going to see what the spare I'm being given looks like and if it's good to go I'm going to not mess with this! However from the S/M it seems very straigh forward if you just check everything twice.. I'll enjoy the challenge.. and I agree I want my boat to be fun and reliable.. I want to worry about the hot bold on the bow in a bikini not whether or not my ride is going to hold together so I'll go with genuine parts. and I was wrong the water pump is $40 up here at bass pro next door to my house.. thanks guys oh by the way ziggy I know the gears are good I have it all torn down.. it's getting it back together that i'm worried about!!

 

[rodbolt]

Re: mercruser 140 drive shaft sheared

ok, as all you are replacing is the drive shaft and bearing before doing anything record pinion height,and backlash.
used gears dont generally like to change the wear pattern.
how you accomplish this is up to you, buy the tooling or make your own.
your not shimming anything but the pinion gear back to its proper location to the propshaft centerline.
to deep and its noisy and selfdestructs rapidly due to lack of root clearence, to shollow and its noisy due to excessive lash and failure occurs due to excessive gear load on the heel area of the driven gear and the toe area of the drive gear.

gears is simply gears, doesnt matter what its on, a lathe headstock,a spicer rear end or a verticle to horizontal transmission.
they must be assembled with the correct tooth contact patten,rolling torque(where applicable) and backlash.
so if your handy and have a few tools its not hard at all, just when reusing used power transmission gears remember, they dont like running in a new wear pattern.