i just purchased a 1973 cobalt 19' br boat w/351omc. its locked up, any ideas or secret to try and free it?

Answer 1

First off before trying anything, I have to give you some bad news. You drive package by year will make it an electric shift stringer mount. The last year they were made was around 1977 then went to two other generations of drives before the OMC Cobra drive came out in 1984.
Are you sure it is the motor and not the outdrive locked up? On the top of the drive the is a slotted screw head about the size of a nickel. It is the dip stick for the upper drive oil. If it looks like milk, it has water mixed with the oil, possible phase separated by now. Look on the left side of the upper drive and you will see another screw about half way way down, you will need to have the drive in a right turn to see it, remove it. Does water come out? If so the drive maybe locked up.
If in doubt, you can pull the drive back far enough to disengage the ball gears. Then try to turn both the drive then the motor.
Let me know if you need more instructions to pull the drive back.

Answer 2

You can pull the spark plugs and pour just a cap full or two (or three) of either just plain old motor oil or something called "Marvelous Mystery Oil" (I would try the Mystery oil) get it at any auto parts store (old timers will know it immediately). Put the plugs back in and give it about a week.

Then take plugs back out and turn it from the pulley on front of the motor (by hand) or try to crank it with the starter. Once it moves, use the old plugs (you're going to foul them so use the old ones or buy a cheap set).

It's going to smoke like you set it on fire, don't worry about it though, you'll be able to see the rest of the houses on your block in about 20 minutes :) but do expect heavy white smoke.

Repeat this once a week fr about 2 weeks and you're good to go.

When you're putting her away for the winter throw a cap or two full into the spark plug holes again and let it set until spring. This prevents it from locking up over the winter and through the wet, rainy, season (in the spring)...

Don't try that vinegar suggestion, I think that guy might have been storing his boat maintenace manuals in with Grandma's pickling recipes.

You'll destroy the rubber seals and damage all of the aluminum surfaces with vinegar.

You may however, celebrate it's first start by throwing a shot of scotch down the carburetor throat once it is running........ It definitely wouldn't hurt if you tossed it into your carbeurator instead

Time, patience, it'll break free, I promise..... If your in a rush, put the oil in now, try turning it in an hour and keep trying each day, twice a day, until it breaks....

Always remember to put the plugs back it to keep the moisture out while the oil soaks in....

Answer 3

If its locked up from sitting ( Rust ) try diesel and light oil first ( Marvels ) . If that doesn't work put vinegar in the cylinders , but be careful it well cause pitting if you leave it in to long . Trust me I've done it .

Answer 4

Your engine is seized up or the upper out drive housing is. Have the engine pulled and an expert rebuild.

Answer 5

get another ,now you know why the boat was sold to you

Answer 6

have it done if you have to ask here lol