What is the trick for getting the lower unit onto motor of 1989 35hp Merc

[Kirscher]

OK. Here goes. I have read many threads regarding how difficult it was to remove the lower unit from a 1989 35hp Merc engine, especially if it has not been removed for a while. Mine had never been removed in 19 years so I expected the worse. What a challenge. It took me 52 minutes which includes draining the oil and putting in a new impeller and seals. Hey this is easy.

Here is the rub. For the next 5 1/2 hours, I attempted to get the lower unit back into the upper housing. The problem that I have been encountering is the four items that have to be aligned properly to get them all to go in correctly and remain in alignment. The items are: 1) the water tube, 2) the drive shaft, 3) the exhaust tube with rubber gasket that needs to be on, and 4) the shift shaft. The rubber gasket or seal fits on the end of the exhaust tube making it difficult to get the other things in as well.

Can anyone tell me the trick to assembling the motor?:redface:

 

[emckelvy]

Re: What is the trick for getting the lower unit onto motor of 1989 35hp Merc

I'm thinkin' the exhaust tube rubber seal should be firmly positioned into the gearcase and not placed on the end of the exhaust tube. Although it may have come out on the end of the tube.

Typically it'd be in the lower unit with the exhaust tube coming down to meet. I can imagine that if it's on the end of the exhaust tube, that's gonna keep things from seating properly.

Other tip, shift both gearbox and lower unit to Neutral. The shift shaft on your 35hp rotates CCW from Fwd to Neutral to Rev. There should be about 270 deg of free motion on the shift shaft when the L/U is in Fwd. But as soon as you rotate CCW you'll reach a point of resistance. Further rotation CCW shifts into Neutral.

If you do need to manually shift the L/U, be sure to wrap some tape around, or otherwise cushion, the jaws of pliers or Vise Grips etc, used to move the shift shaft. Otherwise you could mar the splines on the shift shaft, making installation even more difficult!

Now, sometimes the doggone shaft splines just don't wanna line up regardless of what you do, in that case you may have to disconnect the shift cable from the shifter arm, up in the powerhead. Then you can "jiggle" the shifter arm to and fro a few degrees to line up the shift shaft.

Just be sure to note the approximate position of the upper shift arm, when in Neutral, before you disconnect the shift cable. Then you'll have a good idea where it should be when you reinstall the L/U.

Shine a light into the 'gap' between L/U and exhaust tower, when you're inserting the L/U. You'll be able to sight the water tube entering the pump; at about the same time, the driveshaft's gonna wanna engage, and you'll need to turn the flywheel a few degrees to align crankshaft and driveshaft splines.

BE SURE SPARK PLUGS WIRES ARE PULLED before turning the flywheel! :0

Very shortly thereafter comes the shift shaft, and the exhaust tube usually brings up the rear! It does help if you grease up the I.D. of the rubber gasket, and the O.D. of the exhaust tube.

Note if the rubber gasket is torn on the inside, or warped inwards, the exhaust tube will catch on the gasket instead of slipping into place. In that case it's best to renew the gasket. Or, completely clean and degrease both gasket and L/U where the gasket sits, and use some contact cement to hold the gasket in position.

That should just about do it, you oughter have that L/U back on in 10 minutes or less!!!!

HTH.......ed

 

[Kirscher]

Re: What is the trick for getting the lower unit onto motor of 1989 35hp Merc

Thanks for the prompt reply. Your reply brings up a new question. From your reply, it appears that the water pickup tube should be installed first in the engine and not in the lower unit. Is this assumption correct? If that is the case, then there will be only 3 items to raise into place rather than 4. The water pick up tube appears to be the main culpert since it has some freedom to move. So my new question is: Should I remove the water pickup tube from the lower unit and install it in the engine rather than have it first installed in the lower unit?

 

[emckelvy]

Re: What is the trick for getting the lower unit onto motor of 1989 35hp Merc

There's the root of your problem; the water tube is NOT supposed to come down with the lower unit.

Unfortunately, as you've experienced, it sometimes does. What you'll want to do is get that copper water tube out of the pump and reinstall it in the upper end. Real fun to do since it's SO easy to see up there!

But if you shine a strong light you should be able to see where it goes, into a rubber grommet very similar to the grommet in the upper pump housing.

Lube up the O.D. of the water tube with Permatex Aviation-type non-hardening gasket dressing. This'll keep the tube from falling down so readily next time the lower unit is removed. If you don't have any handy, just slather some waterproof boat bearing grease (I like the blue Sta-Lube stuff) on both ends of the tube.

The Good News is, since the tube pulled out so readily, you probably don't have any corrosion issues up Topside and it'll go right back in. I've seen the upper water tube grommet so full of corrosion products that it squeezes the copper tube almost shut and that's a Bugger to fix!

Yours probably looks like brand new.

You should find it MUCH easier to get things together without having to fight that water tube!!!

Cheers.........ed

 

[Kirscher]

Re: What is the trick for getting the lower unit onto motor of 1989 35hp Merc

Thanks for all the help. I shall try this next Saturday when I go back to the lake.

 

[Kirscher]

Re: What is the trick for getting the lower unit onto motor of 1989 35hp Merc

Thanks for all your help. Both suggestions were well proven to help; i.e the water tube had to be in the engine and not in the lower unit to mount the two together and the rubber seal at the lower portion of the exhaust tube had to be placed in the lower unit prior to joining the lower unit to the power head.

Again, thanks