4.3l locked up

Need some advice. I got my hands on a 1993 Crownline with a 4.3l mercruiser and I'm being told it is locked up. Well I want to get this boat up and running so I have taken on the challenge. I removed all the plugs squirted WD-40 into each plug and let it sit for 30 mins. I also removed all the belts.Then I took a 3/8 drive and put it on the front pulley and tried turning CCW it moved about 1/8 of inch and stopped. I only had a 3/8 drive at the time so i might not have had enough strength to turn it. I didn't want to force it because i have read on a few different blogs that the out-dive can sometimes cause this problem? So that's my real question is there something in the out-drive that could cause this, I haven't had time to mess with it in the last few days. In the past I have had some people respond with junk it or run from it. So please if you have some good advice please provide.

Re: 4.3l locked up

pull the drive first to isolate engine or drive trouble, avoid using the nose bolt on the crank. better off removing the front pully and installing bolts in the 3 holes and use a bar between the bolts.

Re: 4.3l locked up

Head to ur nearest auto supply store and get some marvel mystery oil i hear it works miracles and if you can get any play buy using the suggestion above just work the mystery oil in going back and forth untill it rotates all around

Re: 4.3l locked up

Thanks, this is the kind of advice I am looking for. Now just to help me understand the working relationship with the motor and the out -drive. I have taken the automotive approach and I viewed it as if the car was still in park I can still rotate the engine by hand. I know we are talking cars and Boats just trying to grasp what in the out-drive would cause this type of problem. I am just trying to understand, so if I can rotate the prop when it is in neutral that doesn't mean its in neutral? I like your idea on the three bolts because as I was applying pressure I was worried about snapping off the bolt. Once again thanks for the info and please keep it coming I like to learn, and man do you guys have a lot of GREAT knowledge.

Re: 4.3l locked up

The outdrive offers a fair amount of resistance, and it is directly connected to the engine. So, in addition to turning the engine, you are turning most of the gears in the outdrive. It is like trying to start a car that is in gear.

By removing th outdrive, you are left with just the engine to turn. You should go for the 1/2 drive socket with a breaker bar. Use fogging oil or mystery oil, not wd-40

Go CW as you look at the front of the engine.

Re: 4.3l locked up

For an easy car analogy to understand, think of the engine and outdrive relationship as like a car engine with a manual transmission, only there is no clutch so to speak between the input shaft of the drive and the back of the engine. The input shaft from the engine to the drive is always spinning, and the drive is what shifts in and out of gears, and has clutches to accomplish this. If something in the drive has fouled up, it could potentially lock the input shaft to the point that it stops the engine from spinning.

As others have said, pull the drive and see if it frees up. You can get a brand new SEI drive for a song to replace it if need be. If the engine still fights you, IMHO you need to pull it apart. Short of a very mild ring seizure due to rust (which you would most likely be able to break free anyway), I don't think I would trust an engine that I had to break free with brute force. If that's the case with your engine, and you insist on getting it running with out pulling it apart, you would probably either find it runs very poor due to low compression, or if the engine has spun/trashed bearing(s), the next event would most likely be throwing a rod through the block.

Re: 4.3l locked up

Aquatron said:

Thanks, this is the kind of advice I am looking for. Now just to help me understand the working relationship with the motor and the out -drive. I have taken the automotive approach and I viewed it as if the car was still in park I can still rotate the engine by hand. I know we are talking cars and Boats just trying to grasp what in the out-drive would cause this type of problem. I am just trying to understand, so if I can rotate the prop when it is in neutral that doesn't mean its in neutral? I like your idea on the three bolts because as I was applying pressure I was worried about snapping off the bolt. Once again thanks for the info and please keep it coming I like to learn, and man do you guys have a lot of GREAT knowledge.

Click to expand...

Ayuh,.... Remove the 6 nuts, 'n the pin through the trim rams, 'n Pull.....

If it's an Alpha, it's 'bout 80lbs.... Bravo, 'bout 110lbs or so...

The upper gear set, in both, turns with the crankshaft....
A blown upper can easily lock the motor...

Re: 4.3l locked up

As other have stated. you need to seperate a motor problem from an outdrive problem.

With the drive in neutral, eveything in the outdrive still rotates with the engine Except the final output shaft that the Prop is mounted on.
When the outdrive is in neutral, 90% of it is still in gear.

Re: 4.3l locked up

ya listen to bondo and separate as that will make things easier no matter which way you go. If you do get it free if it dosent rotate i say with a little less then 10lbs of force w/o plugs then you probably need to rebuild er' other wise if by some miracle you get it running it will either thro a rod or permanently seize do to bad bearings and that would make it almost impossible to break free during a rebuild.

just my .02 so ur up to .04 cents wanna buy stock in BlackBerry hah lol jk

Re: 4.3l locked up

Just a word of encouragement if nothing else,
My brother had an old 4 cylinder volvo that he bought siezed for dirt cheap, pulled the drive, plugs, oiled it up, etc. Broke it free with a big breaker bar and lots of elbow grease and it ran great for years until he sold it.

Good luck and keep us posted!

Re: 4.3l locked up

I would remove the drive, while having mystery oil been sitting in the plug holes for a few days. leave plugs out and try to rotate it if it will rotate put a good battery in it and see if the starter will turn it over(plugs still out) I would also drain the oil just to have a good look at it. Any water in the oil would have me super concerned of the condition of the interrnals. If it will turn over normally with the starter post back for info as to your next steps. Good luck...

Re: 4.3l locked up

Thanks, for all the great advice. I'm busy at work so this weekend the drive is coming off and mystery oil will be added. This has been a big help and a BIG COST SAVINGS at this point. I'm SO SO glad I posted my thoughts to you guys. I had heard how the out-drive could cause this problem. Now i have a good understanding on how the out-drive works with the engine. I'm not out of the woods yet still things to ck out and it could be the motor, but if it is I will know for sure that it's the problem. Thanks, again and i will keep you posted.