Need some general direction - for my neighbors kid

harringtondav

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Sorry about the lack of s/n etc. I'm flying blind here. My neighbor's son bought a money pit Mid '80's Bayliner cuddy 18-19' 3.0L OMC drive. He has a serious oil leak which I'm pretty sure is the oil seal in the front cover. I agreed to show him how to replace it - meaning I'd do it later this spring.

I just talked to him to verify the offer. He said, "Great, um, but I also whalloped the prop and now the whole thing is kinda wobbly".

W/o any more info I guessing he bent his prop shaft. I told him that if it is bent, I can't (won't) help. The prop is a pin drive, and that's all I know. I'm fully tooled for a Merc Alpha II and know the ropes for prop shaft replacement.

My question is if this vintage OMC follows the same disassembly process as the Alpha II? I doubt if my three Merc special tools would any good. I told him to get an estimate on a repair or a used prop shaft hsg before he spends another dime.

Thanks for your input.
 

wrench 3

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If the prop has a pin through it with a plastic cone and cotter pin to retain it, it's an electric shift that was last produced in 1976.
The good news is, it can be repaired without special tools with a bit of ingenuity.
The bad news is, the parts are getting very hard to find.
 

Redrig

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can you grab a pic of the drive ? mid 80s could be one of a few different OMC drives.

but as wrench pointed out , pin drive prop means electric shift (up to 1977)
 

harringtondav

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can you grab a pic of the drive ? mid 80s could be one of a few different OMC drives.

but as wrench pointed out , pin drive prop means electric shift (up to 1977)

I'll see if I can get the kid to send me a pic. My pa in law bought a '75 OMC 302 Ford w/electric shift. It trimmed by hyd front motor mounts and had a large transom rubber boot as a seal with a 'cog' drive coupling w/pin prop pin drive.

The kid's drive seems more current from what I remember. It had trim cylinders. I'll test his resolve and see what he can provide. ..Not even sure he knows how the prop is attached. I'm more sure he has learned a le$$on.
 

Scott Danforth

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78-80 were first of the hydro-mechanical shift stringer 400's behind the 3.0

81-85 was the mechanical shift stringer 400's behind the 3.0

86 was the first of the cobra drives
 

southkogs

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Early OMC Stringers mostly trim on the front of the engine using an electric motor, later Stringers had a hydraulic set on the front of the engine. None of the Stringers use rams on the drive for trim or tilt. That's a fast test you can use - if it's got rams, you know you're into a Cobra.

Depending on how bad he whacked the lower, it may be just as easy to find a used replacement (as opposed to finding parts and rebuilding).
 

kenny nunez

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AS far as the oil leak, the timing cover is most probably rusted out. There is a void the way it is made and that area never got painted. Easy to replace. Cut the old gaskets flush with the block and use a good grade of RTV in place.
As far as the drive you never know what a Bayliner has. This package may have come from a boat they took back because of a defective hull and used it later.
Hopefully the prop shaft is not bent. I have replaced prop shafts without taking the drive apart but it is not the way the factory wants it to be done.
 

harringtondav

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Early OMC Stringers mostly trim on the front of the engine using an electric motor, later Stringers had a hydraulic set on the front of the engine.

..off my original question, but I have to admit that '75 Stinger was sweet. The electric shift was smooth. I'm assuming cone clutches(?). And that +- 90 degree steering angle angle was awesome for fetching a downed skier.

That Sea Sprite Sea Nymph mod tri-hull lasted 23 yrs. with no serious mechanical problems. Pretty good considering at least 16 users with no skin in the game. It looked like it had been through a demolition derby with most operators force feeding it back into the Shore Station.

It finally died when the structure under the front mounts rotted and allowed the engine to shift and pinch a tear in that transom seal. It almost sank with one of the young nephews driving. He had the presence of mind to get to another open boat lift on the lake.

Generous pa in law replaced it with an 18' Crownline BR w/4.3 Gen II Vortec. It hasn't fared so well with multiple operators. One new engine, one new O/D in 20 yrs. Apparently that 302/Stinger was close to bullet proof.
 

Scott Danforth

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I have replaced the prop shaft twice in my old OMG stringer - once because it was bent, and once because my sister picked up a rock with the stainless prop and sheared off the shaft. you can do it with the drive still mounted, however as Kenny mentioned, that is not how it should be done.

all 3.0 stringer 400's have a ball-screw actuator at front of the motor for trim and they trim by tilting the whole motor/drive assembly

Hydraulic mounts were on the V-engines

if it has a big boot in the back that the drive comes thru - its a stringer
early hydro-mechanical stringers were white, later mechanical were light silver

if it has two hydraulic rams it will be a cobra (dark silver)
 

garbageguy

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... get an estimate on a repair or a used prop shaft hsg before he spends another dime...

Maybe a quote on anything else it might need to be the boat he wants it to be (at least safe?) - before spending another dime. Maybe it's a creampuff and worth putting a lot of time and money into...
 

harringtondav

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Maybe it's a creampuff and worth putting a lot of time and money into...
Doubtful. I spent over an hour in it last summer shaking down that engine oil leak. That black hard sealant under the motor mount didn't look good.

if it has two hydraulic rams it will be a cobra (dark silver)
Thanks Scott. I'm nearly certain it's a Cobra. Thinking the kid is confused on the prop attachment. I looked at the repair at Boatinfo. The Cobra appears to be a clone of a Merc.

The good news is the prop shaft housing can be disassembled without any special spanners. My Alpha seal carrier puller rig will work, and I'm hoping my prop pinion tools will fit. The pinion nut is the same as the Merc. If my spline socket doesn't fit, I can figure out how to hold it and not damage the splines. Getting that 70 fl lb of torque will be a challenge.

The bad news is I'll probably cave and fix his bent prop shaft. But he has three young kids and wants to take the boat to the Mississippi. So once I open that tar baby I'm afraid I'll find myself getting deeper. New water pump impeller, seals, etc. I want him to be safe.

I'd appreciate knowing any other pitfalls before I dive in. Thanks.
 

Scott Danforth

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SEI has conversion kits and a new drive that would put your mind at ease.
 

jimmbo

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..off my original question, but I have to admit that '75 Stinger was sweet. The electric shift was smooth. I'm assuming cone clutches(?).

You assume wrong, The Electric Shifts used what was basically Spring Coils that were attached to the forward and reverse gears. An Electromagnet would draw the spring towards it, the spring would wrap itself around a Hub that was splined to the Prop Shaft and would result in a lockup. When power was cut to the Electromagnet, the spring would retract, releasing the hub and the prop shaft was again in neutral
 

southkogs

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^^^ Yup. Which was a great way to deliver power. The shifting was smooth and the power was instant. And you're right the side to side steering on the OMC was fantastic for steering too. The other thing that the Stringer delivered was "quiet." When just at idle or no-wake speeds, you couldn't hear my engine running. The water behind the boat was nosier than the engine was.

They had their trouble, but the drives had some nice advantages too.
 

harringtondav

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I've been spending my ample retired, winter shut-in time researching the Cobra drive. Kinda interesting. It seems complicated compared to the Merc Alpha. Many bearing carriers, two piece lower drive shaft, face thrust bearings + needle bearings vs. tapered roller, etc. The sea water pump looks nice for repair, but also seems cost.y

I'm guessing OMC had to change it up enough to avoid patent infringement. But complexity = cost. Wonder if that led to OMC's demise? Also for those of you who have performed open heart surgery on both OMC and Merc, I'm wondering about the Cobra's reliability and ease of repair?
 

jimmbo

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OMC kept their Stringer Drives until the Patents that Volvo had, expired. I don't think Mercury ever paid Volvo a cent even though is copied a lot of the design of the Volvo. Interestingly, the Volvo I/O, the Mercrusier, and the Cobra were the result of one man, Charlie Strang.

The Cobra drive came along in the Mid 80s, FICHT is what led to OMCs demise in 2000.
 

harringtondav

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I'm getting ready to dive into the neighbor's 1988 Cobra s/n 10553845 3.0L. I've been studying Boatinfo on the procedure to remove his bent prop shaft. I know my Merc Alpha II like the back of my hand, so I'm fairly confident I can handle the repair.
But a few questions:
- Does the helm shifter need to be in FWD or any special position before pulling the drive?
- I didn't see a speedo connection. Is there one?
- I'm (neighbor) going to purchase OMC 311875 pinion shaft socket to remove the pinion nut. The manual shows a special nut wrench 334455. Pricey for a long handled OE wrench. The nut is the same p/n as my Alpha. Will my Merc 91-61067 A3 pinion nut adapter fit over the Cobra's dog clutch? If not I'll weld a handle on an OE wrench.
- I found two OEM prop shafts: 0387818 $280, superseded by 0436888 $323. Both in stock. Will the 0387818 work?

This will help me get started. But by the looks of his Swiss cheese exhaust bellows, and stripped pinion bearing retaining screw, I'm guessing I'll be back for more pointers. And my neighbor will be digging deeper into his pocket for more parts.
Thanks, Dave
 
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kpg7121

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I'm getting ready to dive into the neighbor's 1988 Cobra s/n 10553845 3.0L. I've been studying Boatinfo on the procedure to remove his bent prop shaft. I know my Merc Alpha II like the back of my hand, so I'm fairly confident I can handle the repair.
But a few questions:
- Does the helm shifter need to be in FWD or any special position before pulling the drive?
- I didn't see a speedo connection. Is there one?
- I'm (neighbor) going to purchase OMC 311875 pinion shaft socket to remove the pinion nut. The manual shows a special nut wrench 334455. Pricey for a long handled OE wrench. The nut is the same p/n as my Alpha. Will my Merc 91-61067 A3 pinion nut adapter fit over the Cobra's dog clutch? If not I'll weld a handle on an OE wrench.
- I found two OEM prop shafts: 0387818 $280, superseded by 0436888 $323. Both in stock. Will the 0387818 work?

This will help me get started. But by the looks of his Swiss cheese exhaust bellows, and stripped pinion bearing retaining screw, I'm guessing I'll be back for more pointers. And my neighbor will be digging deeper into his pocket for more parts.
Thanks, Dave

Drive has to be in neutral when pulling or reattaching that drive. While you have the drive off may as well check u-joint bellows, gimbal bearing & u- joints. Cheap insurance, parts not that expensive & not too difficult to replace. If they check out ok, pump some grease in if needed. One very important point. When you refill that drive do not fill it from bottom drain plug, or he'll grenade the drive in no time flat. Fill it ftom the middle plug on starboard side to avoid an air pocket. It will take about 2 quarts. When I was wrenching on mine I would fill it, wait a few hours & check it again before running it. There's a quart pump you can buy with a fitting on the end that will screw into that middle fill plug. Makes it a lot easier.

Those Cobras are good drives. They're nearly bullet proof with proper maintenance. The shift cable adjustments can be a p.i.t.a. but if it's adjusted properly you can shift that sucker with one finger. Good luck!
 

wrench 3

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There's no speedo hookup.
I just fabricated the wrench so I don't know its the merc tool will work.
BTW the exhaust bellows comes with holes in it.
 
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