Help re: Bent Shaft on Merc 850

[wguttrid]

Hi guys been restoring a 16' wilker and on the last stages, those being the engine which is a Merc 850 (circa 73-1974) . Hoping to get it out for our Canadian long weekend, and sure you will know what I mean by saying the girlfriend is about ready to kill me cause I have been saying just another 2 weeks for about 3 months now.

Just dial guaged the prop on the new lower unit installed before mounting the prop from the old one and lets just say you don\t need a guage to see the thing is out. Luckily the old prop is only out about .003 at the end.

So looking at swapping out the old prop shaft and putting it on this lower unit, main question is before I get started tonight (going to be a late one, lol), do I need to remove the complete lower unit or can I remove the prop shaft with out dropping the lower unit?? Hoping the later is the case...lol

Have a schematic of the lower end and need to get back to the cross-pin to free the prop shaft.

Well it is coffee time, lol.

 

[Moody Blue]

Re: Help re: Bent Shaft on Merc 850

Yes, the prop shaft is removeable without having to drop the lower unit.

You remove the complete bearing carrier with prop shaft and reverse gear as one from the lower unit housing. Bearing carrier is held in place with a large tabbed nut and a locking fingered collar. Bend up the locking finger then unscrew the large nut (not easy without the proper tool). Will need either a puller or slide hammer to remove the carrier from the housing. It won't come out willingly. Oh, and drain the oil before you get started or you'll have a bunch of oil on the floor. You will need a new o-ring for the carrier housing and new seals for the prop shaft.

 

[wguttrid]

Re: Help re: Bent Shaft on Merc 850

Thanks Moody Blue, better get on the phone and tell the girlfriend it is going to be another 2 weeks.

Makes sense, but looks like this weekend is a no go as going to need to order some parts...darn.

Do you think for a weekend only, I could use the old o-ring and seals permitting I don't buggger up this special nut.

Temp fix just to at least get it out on the water and baby the engine.

 

[Wingedwheel]

Re: Help re: Bent Shaft on Merc 850

If you use the old O-ring you should be OK for the weekend as long as you don't nick it taking it out although a dealer should carry that and its not expensive. The carrier will come out easier the second time and when you replace the o-rings, replace the prop-shaft seals too. Also there will be a shim or two inside the gear housing. Make sure you get those back in as they are VERY important.

 

[wguttrid]

Re: Help re: Bent Shaft on Merc 850

Been busy with other stuff so just getting back to the engine problem I had before, curious does anyone know the tool part number I need to remove the special nut?

 

[wguttrid]

Re: Help re: Bent Shaft on Merc 850

Actually found this link related to merc tools, curious is the one I require shown?

http://www.boatfix.com/merc/Tools/tool1.pdf

 

[zorak]

Re: Help re: Bent Shaft on Merc 850

I tell you what i did.My prop shaft was bent.I was in the same situation with the Mrs.I didnt have any more money in the budget to fix my bent shaft.Now i don't know how much yours is bent and i know it's not the right way to fix it but i put a piece of copper pipe over the shaft then used a piece of sch 80 pipe to bend it straight.i got the idea from a company that uses a pull a power with a special rig to do the same thing.Of course i used a dial gauge to check the runout and i went slowly. I was lucky enough to get it to .003. i will tear down the lower unit this winter and straighten it right,plus i will also inspect the bearings.As of now the shaft turns very smoothly and i can feel no vibration when the motor runs.Like i said not the right way to fix it but i beats going to the wife and telling her you need MORE money.

 

[Dave1027]

Re: Help re: Bent Shaft on Merc 850

Zorak, did you do this with the propshaft still in the lower unit?

 

[wguttrid]

Re: Help re: Bent Shaft on Merc 850

Zorak, great idea!

Same as above did you do this while it was still in the lower unit?

 

[zorak]

Re: Help re: Bent Shaft on Merc 850

Yes.It was still in the lower unit.I used a c-clamp attached to the skeg as an attachment point for the dial gauge.The copper pipe was to protect the prop shaft from nicks or gouges.I used SCH 80 pipe approx 6 foot long which still bent under the stress.If you try this be carefull as you could make it worse.I marked the high side of the shaft with a sharpie and put that mark straight up.I bent it a small amount at a time and rechecked it after every attempt.I had .022 of runout and i managed to get it down to .003 .I have been told the factory max is .006.Now keep in mind this will put a lot of stress on the transom as well .Mine is new and althought i did hear 1 small pop it held just fine.If you don't straighten it any on the 1st attempt then go a little harder on the next attempt.Good luck .Keep me in the loop as to how it works out.

 

[wguttrid]

Re: Help re: Bent Shaft on Merc 850

Hey Zorak thanks for the idea about straightening the prop shaft, might be trying that one out at some point.

Quick update, managed to pull out the propeller shaft for the old lower unit as well did the same for new lower unit which is on the engine.

Here are my questions hoping someone can help me out with, will separate them between the two lower units

Old Lower Unit (sitting on bench in vice)
Problem - Reverse does not work.
Inspection - Forward and reverse gear appear to be in very good shape. The only issue I can see is the pinion gear has one spline that is damaged (gouged / chipped) and some minor wear. Sliding clutch dog appears to be in good order when I move with my hand. Gear shifter I am not sure what to be looking for but the cam follower tip is rounded out a bit and the shift cam has a slight gouge.

Did not find any shavings in lower unit but when drained oil there was a good amount of water.

Prop shaft is true.

New Lower Unit (Located on engine)
Problem - Bent shaft and pinion gear has one tooth completely gone and couple other teeth are chipped. Considerable amount of shavings in the area where the bearing carrier sits.
Inspection - Forward and reverse gear in good condition as well the sliding clutch. Shifter for this unit is good and from what I was told there is no issues with forward or reverse gears as well before I bought the guy ran a pressure test and it held pressure for good half hour.

When I drained the oil from LU it was in good shape, no water.

I have on hand new O-ring and seals.

Solution, not sure what I should try here nor what to tell the girlfriend...hahaha. Main goal is to get out on the water a couple times this year on the few weekends left. What I am thinking is to swap out the shafts and put original parts back inot the new lower unit and the couple times I run the boat this summer to make sure I baby the engine and make sure I don't grind the gears when engaging from neutral.

Then once the fall settles in and not in such a rush to do a complete tear down of the lower unit.

So what are everyones thoughts can I get away with swapping shaft props and running as is on a bad pinion gear or should I tear down the LU and rebuild??

 

[Wingedwheel]

Re: Help re: Bent Shaft on Merc 850

If you run it with that chipped gear you run the risk of more damage. Its my understanding that once you break the metal on a part, the integrity of the steel is in question. I guess its much like breaking a claw off a hammer. the integrity is gone and you can shatter another part by still using it even if its on the opposite end. Also those broken teeth could damage your other gears. My 02

 

[wguttrid]

Re: Help re: Bent Shaft on Merc 850

Well guys been busy with the lower unit and have a couple questions, for both lower units I have one cam follower (the piece that goes into the end of the prop shaft) has a nice point while another one has been rounded out considerably over time. Have everythign back together with the rounded one and wondering if this could be causing some shift problems, should I swap it out?

As well here is what I have learned thru this site, hope this is correct.

1.) turning shift rod ccw for forward gear (prop ratchet cw and locks ccw)
2.) turn shift rod ccw for neutral postion (prop free wheel)
3.) ccw for reverse postion (prop ratchet ccw and lock cw)
Note: That it's not really a good idea to rotate the shift shaft CCW past Reverse and definitely don't rotate the shift shaft CW to try and shift back into Reverse, once you've hit Fwd.

As well basically the degress of turn on the shift rod for all gears is 90 degree's.

And one more question, turning the rod by hand should you be able to do this all by finger or do you require vicegrips, cause I notice there is probably a good 180-200 degree's motion (the revsere lock ramp is facing the prop side of the lower unit) that is quite easy to move the shifter but going past this it is very difficult and you need vice grips.

 

[zorak]

Re: Help re: Bent Shaft on Merc 850

not 100% sure about which way to turn shift rod but when in reverse i think the prop shaft shouldn't turn.I had tu use vicegrips to turn the shift shaft ,just be careful to keep from marring up the shifter shaft.Just slide a short piece of rubber hose over it before you vicegrip.i know on my 50 horse that even thought the overall range of motion is pretty close to to what you describe the location of neutral is located in a very small range of the shaft rotation.I know when i reassembled my LU i put it into neutral along with the control box as my 1st try in forward resulted no forward gear,just reverse i think.Your LU is much older than mine so the prop shaft rotation in the different gears may be correct for your engine.i looked on this forum for a link to a manual for your engine but had no success.

 

[Gomer50]

Re: Help re: Bent Shaft on Merc 850

Well I own a 72 merc 80hp when in forward gear prop will rachet one way and turn with the engine the other way,in reverse it will not rachet it will be tight both ways.I put in a set of gears that was missing a tooth in forward and ran it around the lake while I was waiting for my new one (ebay).After I got the new one I decided to gut the old one and come to find out not only was I missing 1 tooth I was missing 6 teeth and my pinion gear was longer useful.When I put my lower unit back on I always do this in neutral,I cant seem to get it right when in forward as the manual suggests.I can advise that you try to make sure your new gear ratio is the same as your old or you will be buying another prop to make up the difference in engine performance (RPM).

 

[wguttrid]

Re: Help re: Bent Shaft on Merc 850

Hi guys thanks for all the help, manage to finally get the lower unit aligned properly...was able to find forward by turning ccw until the prop would ratchet in cw motion, and then contiued turning the shift shaft ccw about 45 degees until I found nuetral....reverse is still and issue but knew that from prevous owner of engine and just going to run the engine a couple times this season anyhow and then rebuild or possible find a newer engine.

Question, where would you say the problem might lie with the revsere, when I had the lower dropped and when the shift shaft is sitting in nuetral and with the aid of vice grips it is incredible hard hard to move it into reverse or at last where reverse shoudl be and you can tell something is just not right...the rest are easy to find.

What woudl you think might be the problem, could it be the cam is worn along with the cam follower? Reverse gear shows no damage, though the clutch dog lugs and lugs on reverse gear are slightly rounded but no major difference then the foward gear mating lugs.

Even with the remote shifter, forward and neutral are easy to move into and out of but reverse is a b**tch.

Hopefully someone has some insight.

Tonight the plan is to try and fire it up out on the water,will see how that goes.

 

[Wingedwheel]

Re: Help re: Bent Shaft on Merc 850

When you say its a b***h to get it into reverse are you saying it won't go in or its hard to turn the shaft? Typically the cam and cam follower wear down. Generally that doesn't make it harder to shift, just doesn't want to go completely into reverse. If you gear is worn or the "lash" is off you may make things easier by shimming. You can check that by wiggling the prop shaft while trying to put it in reverse. If that makes it easier chances are somethings off. The worn clutch dog usually means it was slipping while trying to go into gear because it wasn't making hard contact. That could be the cam and follower. there's normally a small groove the follower rides in on the cam. If thats "burrowed" out it usually needs to be replaced.

 

[wguttrid]

Re: Help re: Bent Shaft on Merc 850

Trying to remeber how it was exactly...to be honest need to try it again as forget the details exactly now...but mainly you could get it to turn where reverse should be but is very very hard..part.....what I really forget now is what the prop side was doing when I was moving the shaft around the reverse positon.

Pretty vague, wish I would have wrote down my exact oberstaions now when the lower was off.

As well the best the PO said was reverse worked when he first had the boat, the next season it went and could not get into reverse.

Going to do your suggestion tonight and move the prop while shifting and see how that feels. The cam defintely had a groove along the one side where the follower rides.

 

[Wingedwheel]

Re: Help re: Bent Shaft on Merc 850

There will be a small groove already in the cam. You should be able to tell if its excessively worn because it will no longer be a "clean" groove(if that makes sense)

 

[wguttrid]

Re: Help re: Bent Shaft on Merc 850

Makes sense,

So hooked up the ear mffs last night and managed to get the engine started up on the first try, though brother was shooting little bit of straight gas into the carbs and had the throttle cables installed wrong into the new remote control I picked up.She roared and reved high (ya not the best thing) and stalled out after 1-3 seconds, and started easy the second time but only let it start up and shut it down.

Dropping the boat off today at marina to have the remote control reinstalled and the cables all adjusted up as running out of patience and rather have this part done by a mechanic to be on the safe sidewith thsese critcal saftey items. After that just need to wire up a new ignition switch choke combo as rigtht now I basically gutted the old merc contorl and have the key switch, choke, neutral start button just laying on the floor loose at the end of the wire harness.

Curious what is the best way to innstall additonal safety kill switch when a boat has been totally re-done?

I was shocked how easy it started and I can defintly see why you always want to un-hook the batteries, pull the spark plug leads, and remove the spark plugs when your working around the prop.