Prop won’t turn, but the powerhead does

[johnyrude200]

I’ll find out the answer to this one by friday afternoon, but for fun, wanted to float this question out to everyone for some light entertainment.

Story – 50hp motor. Previous owner had this on a tiny fiberglass boat rated for a 40hp. Loaded it up with the wife and 3 young ones (12-15). Boat is rated for 890 pounds…persons + gear. You’re getting the picture now.

Owner stated he "spent 45 minutes explaining to the wife how to tow him on a tube and steer the boat safely with the kids." The beam on this boat is about 4 feet…and that might be generous…only flotation on the boat is the closed bow sytrofoam. It is a 14′ single hull fiberglass boat with no seats…only a small cross member molded into the floor at the helm.

He’s on the tube, she guns it in a straight line, and within 10 seconds, decides to do as hard a starboard turn as the steering wheel would allow.

According to him, the last thing he remembers before bailing and going under water (and from what I can only imagine had to have been at least 25-30mph with that size motor on that small a vessel), is seeing the boat standing up on the transom (literally, and everyone flying overboard opposite of the turn direction).

So he surfaces, and makes sure he sees his family bobbing up and down via lifevests, but the motor is still WOT, the boat has righted itself, but it’s not going anywhere. He swam over, reached over the gunnel and shut the motor off via the key. They paddled in and that was the last time the motor was run (about 4-6 years ago). It’s sat since and I own it now.

He did show me the port side screws holding the lower steering bracket in (usually the clamshells at the bottom of the swivel bracket), and how both of them were snapped in half. That’s as far as I got with it tonight, and Friday morning (or if things are optimum, tomorrow), I’ll get the gearcase off to look further. Votes on the culprit??? Rest of the motor looks OK right now (wouldn’t be surprised if that assessment changes in the next 48 hours).

[fleetwin]

Perhaps the driveshaft or pinion has snapped, not uncommon with these gearcases. THANK GOD no one was killed.
PS- sure hope I’m wrong.

[johnyrude200]

So I finally pulled the gearcase down. Boy, it is a PIA to get at the upper shift shaft screw located beneath the carbs. I had to remove the starter and VRO to gain access, which means I pulled the airbox off too!

Anyway, the driveshaft was broken in half but the gearbox is still seized up. It shifts freely, but I can’t turn the driveshaft nub even with a vice grip.. Looks as if I’ll be doing a full teardown on my very first 50hp gearbox in the next day or two….

[dan-in-tn]

Been awhile since I’ve done one, but with an 18" extension of the 1/4" variety and a 7/16" wobble socket I believe (shallow head) you put the gearcase in reverse and go under the starter. With a flashlight in one hand (even in daylight) and the long socket in the other get it on the head of the screw first. (Tip: if your wobble sockets are woren like mine are wrap them in electrical tape. They will still flex, but not droop!) Now you can back out the bolt. Carefully remove the socket and remove the bolt and lock washer with mechanical fingers. Practice, the fun thing is putting it back in the dark!

Now Mercury definetly had a better idea here!!

Dan in TN

[johnyrude200]

I got as far as removing the 3 retaining screws for the bearing housing on the prop shaft, but the 3 screw orifices aren’t your standard 1/4 inch thread. They’re something slightly bigger, so I’ll be off to the hardware store to look for some 5/16 or 3/8 threaded rod. This gearcase uses 3 of these screws, where as apparently the ’88 models only use two (according to the service manual).

If anyone knows what size these threads are and where to pick up some 10-11" screws, that would be helpful. I’m dead in the water right now until going any further. Looking at the repair manual, I’m wondering if there is more to yanking the driveshaft than on the smaller motors (which just come right out once the impeller housing is removed).

There has to be some frozen gears down in there, or the driveshaft was twisted/bent and became stuck in the driveshaft orifice in the housing. Must have been one heck of an accident to make the driveshaft break in half, along with break some of the lower exhaust housing gromet/vibration pad bolts in half.

I’m beginning to wonder if this motor is worth even going through based on what happened to it. The powerhead seems to be in pretty good condition and I don’t think the motor had been used much before this numb-skull accident. What a waste. Good learning motor, I guess.

[dan-in-tn]

Im totally confused as to which motor you are working on? We have told you there are many differences between these model engines and it will be important for us to be sure which model year you are on each time you need help. My above reference for gearcase removal forvthe shift rod was for the ’88 model. It should have three retainer screws for the bearing carrier 1/4" X 28 thread count. I just checked on ME to be sure I remembered.
The ’93 model uses a tabbed gearcase retainer system. There are two tabs top and bottom that retain the bearing carrier. They are 5/16" X 18. You will need to get a piece of hard all thread rod and 4 long nuts (1"). Cut the rod to about 12" long each. Put two nuts on one end of each rod and weld them there. The other nuts will be for pulling. You will need some heavy (thick) washers to fit against your flywheel puller. You may need to tap the two bearing carrier holes so the rods will go all the way to the bottom. Use your puller against the end of the propshaft to pull the carrier out of the gearcase. I use a GearWrench on the long nuts to keep them even as I pull. Hope all of this helps!
Next you will need a 6 sided 5/8" box end wrench that may need to be narrowed a little to get at the pinion nut! We will wait till you get there?

Dan in TN

[johnyrude200]

The gearcase I’m working on now is the ’86 model. Glad to hear your instructions I suspected that would be what the job called for when reviewing the parts diagram/manual. The pinion nut is the new one for me, I’ll see what I can do in terms of tools once I get there.

Last night I had to grind down a 1/4" x 3/8" socket adapter to fit into the thru-hub exhaust orifice to remove those 3 screws. Thankfully I had a 12" socket extension that was narrow enough to get in there. Then I realized I didn’t have any bolts long enough or the right thread size to get at the puller orifices!

The hardware store people will be scratching their heads when I walk in their this morning looking for some hardened bolts with the right thread count…then off to get a couple welded together so they reach!

Thanks for the help!

[retiredoz]

The instructions I’m looking at (for a ’79 55-hp, same gearcase) call for a special pulling legs tool # 320737 to use with a flywheel puller to remove the bearing housing. ME has em at an awful price, but I think I they could be made without too much difficulty. And after that, the fun’s just beginning.
You may well need a special tool (378206) to pull the driveshaft after you’ve figured out how to remove the pinion nut without special tool 316612 to hold the driveshaft. (oh, never mind, I forgot you don’t have the top to yours ! lol)
I have a viable copy of that lower unit somewhere in my stash, available cheap. Contact me if interested.

[dan-in-tn]

I talked with JohnnyRude200 by phone this morning while he was at the hardware store. He is working on the ’86 model now so it removes differently. Your right, but you can usually get them with a slide hammer hook tool if they haven’t been in salt water forever! The driveshaft tool you may be talking about would be the spline socket? You can get around that by grabbing the shaft in the necked down area so any marks don’t screw up future seals. Special tools are ridiculously priced, but can be built with a little effort. You can even make a spline socket next time you see a bad crank, just cut off the lower end and weld a socket to it.

Dan in TN

[retiredoz]

Of course, JR isn’t saving the driveshaft, so ye olde visegrips would work dandy. Might even get away without the drive shaft puller for the same reason.

Just struck me kinda odd to see OMC jump on the ‘special tool’ bandwagon, s’pose some of Carl’s lost boys went over there to design some of their stuff ?

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