Lower Unit Rebuild

[MercS5]

I bought a 19' Boat with a 70hp Force console steer outboard on it. He told me that he owned it for 15 years and last year it died on him in the river. The shop didn't put a wrench on it but told him it was probably a seized bearing in the lower unit and he sold the boat. It was cheap enough that I didn't care about the engine issues. Took it to a local shop and told them what I was told. They said the only thing they could find wrong was water in the fuel line so they replaced the fuel system. It ran fine for about 1 hour then it died. I got it to start up again and heard clunking but made it back to the ramp. Repair shop found the pinion gear was shot and forward gear didn't look great either. I didn't want to give them $1200 so this amateur is going ot try it himself (already regretting it)

I have my new gears and a service manual ready to go. Waiting on seals. I have the lower unit off and cannot get the pinion gear to drop, nor can I pull the drive shaft up. I'm thinking seized bearing on the drive shaft? The manual isn't much help. If anyone has done lower unit work before and can talk me through it, it would be much appreciated. Or.. if anyone is selling a lower unit for a 1995 Force (Mercury) 70hp I would entertain offers. I already purchased the gears for this motor though.

 

[MercS5]

Lower Unit Help

I posted this in the Force forums but I'm going to try here since its a generalized question and its mostly Mercury parts. It is a 1995 Force (by Mercury according to the cowl) 70hp console steer on an aluminum boat. (I don't want to hear questions why I bought a Force). It was a cheap boat with a motor that didn't run and I knew Force's reputation before going into this.

The pinion gear, forward, and reverse gears are shot. I have the Mercury OEM replacement gears on hand, waiting on seals. I've dropped the lower unit and taken the nut off the pinion gear. I can't get the pinion gear off and the drive shaft won't pull up. I'm thinking seized bearings on the drive shaft? Any help would be greatly appreciated. Not sure how to get this out without breaking something.

 

[SkiDad]

it's much easier to swap out the whole lower unit - you should be able to find one for 200-400 bucks on craigslist or ebay. Then just sell the gears and also sell the broken lower unit. I did this this year and it costly me very little.

 

[Frank Acampora]

The pinion is on a locking taper. Even after you remove the pinion nut, you must force the gear off the shaft. To do this you need to pack the lower unit with some thick metal pieces with one piece bearing on the threaded end of the drive shaft. Then you must forcibly drive a wedge between the pieces. It is not easy but when the pinion releases it will do so with a pop, much like a flywheel.

If you decide to buy a whole used lower unit you can use late model 70, 75, or 40 HP. They are all the same.

 

[racerone]

You did not mention removing the nut above the driveshaft thrust bearing.

 

[GA_Boater]

Both topics have been merged. Starting a second topic in different forums only confuses those trying to help you. Replies had been made in both topics, now they are all together.

 

[MercS5]

Thanks for the posting help GA_Boater. It looked like the Force forum wasn't as active as the Mercury for obvious reasons. Another question I have before we go further, the service manual covers all Force motors. I went to lower unit section and found 1991-1995 70-120hp, then there is a section that says 1995-1999 70-120hp. I don't know which category I fall under because my 70hp Force is a 1995.

 

[MercS5]

mitzy If I could find a complete lower unit for that price I would snatch it up in a heartbeat! I've been told that the powerheads go out and lower units should be easy to come by. Sucks that I bought all these parts but I could try selling them on ebay. and Frank, I don't understand completely what you're describing.. Does it push the drive shaft up? The manual makes it sound simple like you remove the nut below the pinion gear and pull up on the drive shaft with two hands. We put a crescent wrench on the keyway for the water pump then stuck a forked pry bar below it and tried driving up. What is the plastic peice that the drive shaft goes through at the water pump? I'd like to remove that to see what's between it and the pinion gear. And that might explain what Racerone is getting at. Because no I didn't remove that nut above the thrust bearing and didn't know it was there

 

[Frank Acampora]

Uh, Yeah, you can pull all day but nothing will happen unless you remove the threaded ring under the water pump. It holds the top bearing in place. Consider yourself lucky if simply pulling up on the drive shaft releases the pinion gear. most are stuck and need persuasion.

 

[GA_Boater]

I hope these are clear, I'm guessing a little. You should be able to Google the part numbers to see the full diagrams. I hope this helps if I got the right parts drawings, they are for a 1995 Force 70.

I believe the drive shaft nut is #7 in this diagram. Mercury Quicksilver P/N 11-812820 1




Is #10 in this diagram the plastic piece under the water pump? Mercury Quicksilver P/N 46-812966A 3 is the latest part and looks different than this drawing.

 

[MercS5]

Number 10 is what I was referring to. Anyone know how to remove this? I didn't want to damage the plastic peice under the water pump. Thanks for the diagram and explanation

 

[SkiDad]

i don't know what state you are in but ... http://newyork.craigslist.org/lgi/boa/4701593484.html

 

[MercS5]

I'm in Central Illinois. New York is a bit of a stretch but for that price I'd pay for shipping of the lower unit if it was compatible with my motor

 

[MercS5]

http://www.ebay.com/itm/331341625827?ssPageName=STRK:MEBIDX:IT&fromMakeTrack=true
if any boat guys out there could tell me. I have a 1995 70hp force that needs a lower unit. Obviously this is an awesome price. How do I know for sure if it is completely compatible for my boat? Also, how safe is it to not buy from a marine dealer? Theres the chance that just because their powerhead was shot, the lower unit isn't all that great either

 

[SkiDad]

well you are always taking a chance - that is what I did this year i bought a whole engine for 200 bucks b/c it had low compression in one piston. used the lower unit (it was fine) but needed some touch up paint. Then sold the engine for 180 bucks b/c it had all the controls and wiring too.

I always like to ask a question to anyone I buy on ebay from before I bid, you can gauge a lot from there answer.