Old Mercruiser 120 locked up

"This is my first post, I am p

"This is my first post, I am pretty mechanically inclined but dont work on boats very much but very confident, so heres my problem:

I just got a older mercruiser(1980ish). Dont know much about the motor besides its a 120hp inline 4, 2 bbl. Anyways threw a battery in and all it does is click cant get on the crank to turn it by hand but my bets guess it is locked up. Not real sure of the history of the boat. What are my options? Should I pull the head off? pull the engine? Is there any "upgrade" motors I could throw in the boat?

If there are some FAQ's you could link me to that would be great too."

"If the motor has water in one

"If the motor has water in one or more cylinders, it won't crank. Pull the plugs and see if it will crank. If it won't, check the starter and see if you can turn the motor over by hand. The click could just be a bad starter- they go bad from sitting and condensation, cranking with a dying battery and not being lubed on a regular basis (annual maintenance).

Pulling a head off- if you do this and don't like what you see it can always be bolted together and used for a rebuild or use it as a core for a reman, new motor or whatever. I would pull the starter first and have it checked out. If you have it rebuilt, make sure they do it to Coast Guard spec- marine starters, alternators and distributors can't produce any spark externally, while it's not much of a problem on a car or truck. Don't buy a car starter."

"Thanks for the quick reply, a

"Thanks for the quick reply, all plugs have been replaced and I poured a small amount of oil in the cylinders to lube it up, the battery is brand new. It sound like the strarter is engaging and it is more of a "clunk.""

"The clunk may be the solenoid

"The clunk may be the solenoid engaging but if the starter is frozen, that's all you'll get. Take the starter out and have it checked- there should be someone near you who rebuilds them properly."

"I will check that today, but

"I will check that today, but in the meantime is there any info on some posssible swaps? or, is it worth it to rebuild this engine if neccasary?"

Before you get to carried away

Before you get to carried away with the engine pull the drive off and make sure it is not locked.

I am not real familar with boa

I am not real familar with boats so a link or a explination on exactly what the "drive" consist of would help.

"BTW:The prop does spin freely

"BTW:The prop does spin freely, if that helps."

"The prop spinning freely mean

"The prop spinning freely means that the drive is in neutral. Look at the drive from the side and think about the direction of the crankshaft. More or less parallel to the water, right? The upper gearcase has a set of gears that changes the direction of the driving force and when it gets to the lower gearcase, it changes direction again. These gears and bearings can be damaged from heat, water (causing rust, wear and failure) and normal wear. If the gearcase(s) are seized, the crankshaft won't turn because there's a coupler at the rear of the motor and this is where the motor's power is transferred to the outdrive. The reference to the drive being locked up means that if it is locked, it won't turn at all.

The first thing I would do is check the starter and if it's bad, rebuild/replace it and see if it cranks. If it doesn't, then remove the outdrive and try it. If it still doesn't crank, the motor is seized, one way or another.

Try cranking it with no spark plugs, its easier on the starter if you end up cranking for an extended period of time."

"Leo,
On the rear of the boat

"Leo,
On the rear of the boat is the outdrive.
It is held on with six 5/8 nuts and two 9/16 nuts that hold the trim rams in place.

Remove the six nuts and one of the nuts from the shaft that goes through the trim rams at the rear of the drive then slide the shaft out of the rams.

If you are not a large person you may need help removing the outdrive.

With all nuts removed and the shifter placed in the forward position pull the outdrive off.

THE DRIVE MUST BE IN FORWARD GEAR OR IT WILL NOT COME OFF.

There is a drive shaft with two U-joints that will flop around as the drive is removed.

This shaft with the U-joints is what connects to the rear of the engine.

It makes no sense to just rebuild the starter until you know if the engine or the drive is locked. There could be nothing wrong with the starter. You won't know until you find if the engine or drive is locked.

With the drive removed see if the shaft with the U-joints will turn. If it does turn the problem is with the engine.

If the engine is the problem remove all the spark plugs and try to turn the crankshaft with a breaker bar on the center bolt on the front of the crankshaft pulley.

Make sure you try to move the crank both ways to make sure the starter drive is not locked in the ring gear.
If you can not turn the engine this way you have a big problem.

You can try spraying oil into the cylinders but it is best to remove the haed and have a look at the cylinders unless you happen to have a bore scope.(tool that you can inspect cylinders without removing the head) If the cylinders are rusted the engine will need rebuilding or re-ringing at the very least.

Best of luck."

120/140 engines are difficult

120/140 engines are difficult to try to turn over by hand. Easy way is to remove the starter and try to turn the flywheel with a pry bar or large screwdriver. If done carefully this will not damage the ring gear. If the flywheel moves freely replace the starter. If it moves very little and springs back then the drive is probably shot. No movement is the engine locked up.