How many bolts to remove lower unit on 75' 20 hp?

[boatster]

Please someone help me. I removed two nuts, one at the front next to the shift linkage and one at the rear under next to the anode. It seems these are the only two bolts required to remove the lower unit but the damn thing wont budge. Am I missing another bolt? I can't imagine where that'd be. I have a 1975 Mercury 200 20 hp motor. Please someone who knows let me know. Thanks a ton.<br /><br />Adam

 

[achris]

Re: How many bolts to remove lower unit on 75' 20 hp?

Adam,<br /><br />Oh dear! The old driveshaft stuck in the crank trick. If you can get some gap between the gearhousing and the driveshaft housing, then invert the lot and squirt a penerating oil onto the driveshaft and let it run down (the old 'up') the shaft and get into the splines. Leave it overnight and then try and get the leg off again. If that doesn't work (and you may have to use quite a bit of 'enthusiasm' on it) the next trick is to chop a hole in the driveshaft housing and get to the splines with the 'red spanner'. Let's hope it doesn't come to that. Maybe some of the other Mercsperts have some other ideas.<br /><br />Chris...........

 

[boatster]

Re: How many bolts to remove lower unit on 75' 20 hp?

Thanks Chris. I just did a search on "stuck lower unit" and read an epic thread of how people began suggesting the use of a shotgun or throw off the cliff trick. I'm not there yet but my patience is short. BTW, how do I spray penetrating oil on the drive shaft? Thanks again.<br /><br />EDIT: Ok I reread your post. I can't get a gap at all. Its stuck shut as if theres another bolt. But I can't seem to find where in the world that other bolt could be. I looked at a very ugly parts breakdown and only saw two bolts that hold it together.<br /><br />Adam

 

[andrewkafp]

Re: How many bolts to remove lower unit on 75' 20 hp?

Try hardwood wedges near either side combined with belting it. Pre-1978 did not have SS shaft and may be a bear to get off, but it will eventually come off.

 

[boatster]

Re: How many bolts to remove lower unit on 75' 20 hp?

I might be mistaken but I believe my motor is a short shaft. If you're implying to be a long shaft ob or not?? But I tried getting a paint scraper wedged inbetween the upper housing and lower unit and I could barely get the sucker in there using a hammer. It seems something else is holding it down like another bolt. That is why I wonder but I looked at a parts sheet and I could only see two possible bolts holding together. If the driveshaft is fused into the powerhead would it be super tight or is it supposed to at least allow me to get a little gap going? Thanks.<br /> <br />Adam

 

[achris]

Re: How many bolts to remove lower unit on 75' 20 hp?

Adam,<br /><br />SS is short for Stainless Steel, not Short Shaft.<br /><br />Just re-read your original post (properly this time ) and if you still have the anode in this will be the problem. I am not sure (been a while since I worked on one of these) but I think there's another nut under the anode.<br /><br />Chris.................

 

[boatster]

Re: How many bolts to remove lower unit on 75' 20 hp?

Ok I'm gonna go down and bang on the sucker some more. Please if you have further suggestions I could use them. I'd hate to have to drill a access throught the side of the housing just to get to the driveshaft! THERE MUST BE A BETTER WAY!! <br /><br />Adam

 

[boatster]

Re: How many bolts to remove lower unit on 75' 20 hp?

Originally posted by achris60:<br /> Adam,<br /><br />SS is short for Stainless Steel, not Short Shaft.<br /><br />Chris.................

ahhh....

 

[boatster]

Re: How many bolts to remove lower unit on 75' 20 hp?

Ok,<br />I'm really beginning to think I'm up sh!t creek here. Could it be that the drive shaft is rusted stuck into my powerhead unit? It seems the lower unit will not come off at all no matter what! I can't even get a gap. It does not even look like the two units budge a mm. Again I removed two nuts, one on the leading edge next to the rubber shock absorbers and shift linkage and the other upside down in front of the big anode under the cavitation plate? Was there supposed to be a third somewhere? I can't find anything else!! Please someone help me..!!!

 

[achris]

Re: How many bolts to remove lower unit on 75' 20 hp?

make sure the anode is off. It's been a while since I worked on one of these and there could be another nut under it.

 

[Keith Buchanan]

Re: How many bolts to remove lower unit on 75' 20 hp?

Even with the driveshaft splines stuck you would normally expect a little gap or movement, has the lower unit dropped even a few millameteres, there should be a tiny amount of vertical play in the bottom bearing and oil seal. And secondly patience is a virtue, if you have read all the posts about stuck splines you will realise it took me three weeks to drop my lower unit recently.<br /><br />Keep us posted...Keith B....now with extra grease in the right place...

 

[DoctorCAD]

Re: How many bolts to remove lower unit on 75' 20 hp?

There is a bolt under a plastic cap in the rear. Did you get it? I just sold my 200, or I'd go look.

 

[Chinewalker]

Re: How many bolts to remove lower unit on 75' 20 hp?

STOP HAMMERING ON THE UNIT!! There are three studs the hold the lower unit in place. The two that you got already, PLUS one more located under the zinc anode in the rear underside of the anti-ventilation plate. You must remove the anode via a 5/16" allen bolt accessed through the hole in the top/rear of the motor leg. Once you remove that the unit should drop down...<br />- Scott

 

[boatster]

Re: How many bolts to remove lower unit on 75' 20 hp?

Thank you. Thank you. I got that other nut out and now the rear half wants to open up but the front doesn't. I think the front stud is stuck in the upper housing (aluminum rust?). I'm gonna try taking the motor off of the transom mount to expose that nut for a little hammer lovin. <br />Wedging it apart seems futile.<br /><br />Thanks again.<br /><br />Adam

 

[steviecops]

Re: How many bolts to remove lower unit on 75' 20 hp?

Hi<br />I'm just about to remove the lower unit on my 20hp Merc. My manual is on order, so the info that's been posted on here is very useful. <br /><br />Could anyone tell me where, and how, I have to dis-connect the gear shift linkage on this engine?<br /><br />I don't know the year, but it's a blue band. (How do you age these engines? I can't find a model number anywhere!)<br /><br />Thanks<br />Steve

 

[Mettaree]

Re: How many bolts to remove lower unit on 75' 20 hp?

Steve: Post the s/n of your motor and we'll get the year to you.<br />

 

[boatster]

Re: How many bolts to remove lower unit on 75' 20 hp?

Sad news all, the driveshaft must be fused to the powerhead cause I could not for the life of me get the lower unit off. I used wedging screwdrivers inbetween the housing etc etc. The front bolt was fused into the drive shaft housing so I had to cut it off with a hack saw that I managed to make a little opening for by wedging screwdrivers between the lower and drive shaft housing. crow bars, tons of wedged screwdrivers and no go!!! Once I pull the screw drivers out it clams shut. I am SOL on this one. And I got it running so smoothly with the carb too. Just can't replace the impeller, what good is it now!!!? Looks like this ones gonna get parted and the rest goes to the dumpster. Unless of course there is another way to get to the driveshaft and powerhead spline from say taking the powerhead apart??? I'm in serious doubt though. Any thoughts?<br /><br />I am majorly defeated. <br /><br />Adam

 

[Keith Buchanan]

Re: How many bolts to remove lower unit on 75' 20 hp?

So far so good at least you have movement now, the rest is perseverance and you may need plenty of it. Get some hard wood wedges in there, open it up as far as possible and pack with metal shims either side of the middle and replace the rear bolt and tighten up untill the front of the leg is under expansion and leave overnight, regularly tighten the bolt a little more. It's funny how these problems can really niggle and take over your life and affect your work, sleepless nights, loss of sex drive etc, but I found that 10 pints of premium beer every night helped.<br /><br />Keep at it and keep us posted...<br /><br />Regards Keith B...

 

[Chinewalker]

Re: How many bolts to remove lower unit on 75' 20 hp?

Hi Boatster,<br /> If you have to sacrifice something, make it the exhaust housing. There are lots of motors out there missing lower units and lots with blown powerheads, but exhaust housings rarely get worn out. Cut through that and give yourself access to the driveshaft. You might be able to work it loose or make a puller to yank it from the powerhead. Just keep in mind that exhasut housing are easier to find than lower units or powerheads and a good machinist/welder can put a driveshaft back together for you.<br />- Scott

 

[quantumleap]

Re: How many bolts to remove lower unit on 75' 20 hp?

The screwdrivers and crowbar ain't gonna cut it. You need to blast it with a sledge to free up the drive shaft. It's not the pressure that does it, it's the shock of the hammer blows that will eventually break it loose. Try the wedges on both sides with two people hitting it at the same time . This will work. Get hard wood or metal shims, not screwdrivers. Get two slege hammers and a friend.