1971 Merc 7.5 Seize or....... ?

[Mpizzle]

Picked up a 71 merc 7.5 off of the original owner for practically free. Says it ran perfectly but has been in storage for several years and see no use. Everything is clean inside and out, but I can't seam to get anything to free up. When I pull the cord it offers no leeway with the shift lever in the up or down position. The lever that controls the transmission of the motor neutral/foward/reverse only has two positions straight up, or back toward the bow, is there suppose to be a third position here? I am afraid the thing is seized up, but don't know where to start. I'd like to be confident that I am getting neutral first....

Opinions?

 

[AMD Rules]

Re: 1971 Merc 7.5 Seize or....... ?

Remove the spark plugs, then do some checks....

Try turning the prop by hand in each shifter position. Prop should freewheel when its in neutral, ratchet cw in forward gear, and not move either direction in reverse.

Note: You may find it only has forward and neutral. To get into reverse requires that the motor be running to avoid damaging/twisting the shift shaft (don't force it). The drive shaft needs to turn in order to mesh the gears properly.

Take the cowling off and try to manually turn the flywheel clockwise by hand. Don't force it, as it should turn easily. If it won't, then remove the lower unit and re-test. You'll want to figure out which i locked up the power head or the gearbox.

Start there, and report back your findings.

 

[Mpizzle]

Re: 1971 Merc 7.5 Seize or....... ?

Well I sort of started doing a couple of those things, but got stuck in each instance. At first, the prop seemed to not move either way, but now it will freewheel in oneposition (Up) and ratchet in the down position, I assume this is at least a good sign although the flywheel still does nothing in either position.

Got the flywheel cowl off, flywheel would not move. Removed the lower unit and found that the flywheel now moves. The problem is in my lower somewhere, where should I start to diagnose the problem?

Matt

 

[Mpizzle]

Re: 1971 Merc 7.5 Seize or....... ?

Go the lower off, removed the water pump to find the shaft bearing underneath it completely corroded. Completely seized up. Anyone know how to remove this seized bearing? It is recessed below the water pump seat and hard to get at. Would it be possible to destroy the existing bearing with a hammer and screwdriver to remove the components without damaging anything on the other side in the lower gearcase?

 

[Chinewalker]

Re: 1971 Merc 7.5 Seize or....... ?

You need to disassemble the gearcase to access the bearing. That involves removing the propshaft retainer, etc. to undo the pinion gear from the driveshaft. Remove the driveshaft and the bearing comes out with it. Then it's easy to get the bearing off.

HIGHLY recommend getting yourself a service manual at this point. Those lower units are worth their weight in gold (almost) and are well worth doing right.

 

[Mpizzle]

Re: 1971 Merc 7.5 Seize or....... ?

Sigh. Sounds fun. Well shop manual is already on the way and in the mail, so that shouldn't be a problem. Guess I might as well order the bearing while I'm at it. What is the likelihood of more corrosion and seizures on the other side of that bearing? Is it even worth it to continue disassembling or is it time to scrap the motor to parts on e-bay.

Everything seams completely mechanically sound and all parts are very clean except for the drive shaft where it enters the lower and the corrosion all begins.

 

[Mpizzle]

Re: 1971 Merc 7.5 Seize or....... ?

Opinions?


Edit, purchased a Seloc subscription tonight.

 

[Chinewalker]

Re: 1971 Merc 7.5 Seize or....... ?

If you can get the lower unit apart and order up the bearing, or even several bearings if it needs them, you can still get it all together without a huge investment. Of course, if the gears and shafts are shot, too, then you're looking for another lower unit. I've had several of the 7.5/9.8 motors over the years and still have a '69 9.8. They're decent little motors and worth putting a bit of time and money into them... Get the unit apart and see where you're at. Then go from there...

- Scott

 

[AMD Rules]

Re: 1971 Merc 7.5 Seize or....... ?

I agree with Scott (as usual)... don't get discouraged. These little lower unit are repairable. Been there, done that.

Post a pic of the condition, so we can better understand what you have to work with.

The bearing carrier is very hard to find, so don't break it when you're removing it. I did, and my wallet is a lot lighter now.

I had the old carbon steel shafts ceramic coated.

 

[Mpizzle]

Re: 1971 Merc 7.5 Seize or....... ?

I would love to post up detailed pictures for you guys, but unfortunately my digital camera fell into Rosario Straight some 3 weeks ago when I was out lingcod fishing If I had better lighting I could probably take some cell phone pix.....

I have been doing a lot of reading on the Seloc site and starte to understand more what I am going to have to do to get at that bearing. As I was reading it came to my attention that the lower should be filled with oil.... should have already known this, but I am more familiar with motorcycle's than outboards. Considering that it is devoid of oil I am going to have to assume there is a leak in (at least) one of the seals somewhere in the lower. Should I fill it with oil and try to diagnose any leaks BEFORE tearing down?

Matt

 

[cell]

Re: 1971 Merc 7.5 Seize or....... ?

Maybe its just me...but if I seen the lower unit in disrepair I would be going through the engine to make sure buying parts is worth it.

Can you fire the engine up without the lower installed?At least check the compression?