Mercruiser 4.3 Crank barely turns over but does move?

[CLi87]

Hi there everyone, I bought a (new to me) 92' Bayliner 2252 with the Mercruiser 4.3 paired to an Alpha one outdrive. The boat has been sitting under covered storage for roughly 10 years, only 292 hours total on the boat though. I checked the engine oil which looked old, but no rust or water from what I can tell, also used a scope to check the cylinders as best I could and the pistons look fine from what I can see, just some surface rust on the cylinder walls. I figured there would be some rust and corrosion so I sprayed in some Wurth Rost Off Max Ice and left it for a day, tried turning the crank by hand and using a rope but nothing, so I completely filled the cylinders with 50/50 ATF/acetone mix and let it sit for another day, still wasn't able to move the crank by hand and I don't have a special GM crank tool, so decided to throw some fresh batteries in and give her a crank to see if I could break the pistons free. Each time I crank, I see the pulley move about half an inch, and I did this 10-15 times and the crank pulley kept slowing moving forward, so I assume the engine isn't completely seized otherwise it shouldn't move at all.

Has anyone been in a similar situation and what do you guys use to move the crank? I'm a BMW technician so I'm familiar with motors in general, just fairly new to marine motors and the GM 4.3.

 

[Bt Doctur]

pull the drive to eliminate that side
I can see, just some surface rust on the cylinder walls. I figured there would be some rust and corrosion so I sprayed in

batting zero from the start , and rust on the walls will tear the rings apart
Obtain a old input shaft from a drive ,weld it to a T bar, insert in coupler , and turn motor
pull the motor for a full rebuild

 

[CLi87]

When you say "pull the drive", do you mean completely remove the Alpha One outdrive from the boat? I had thought about disconnecting the drive but when I looked behind the engine I didn't see any easy way to do so, seems like the entire outdrive has to be removed?

 

[Bt Doctur]

That is the way its done, shift into full fwd, remove the rams, remove the 6 nuts and pull rearward
Remove the top vent plug and see if oil is to the threads, if not probe with a soft item, blade of grass to see how far down the oil level is. If none indicated, loosen and slightly remove the bottom drain plug.If rusty water comes out, remove the drive

 

[CLi87]

Thanks Bt Doctur! I'll go ahead and remove the outdrive and i'll post what I find.

 

[Scott Danforth]

Hi there everyone, I bought a (new to me) 92' Bayliner 2252 with the Mercruiser 4.3 paired to an Alpha one outdrive. The boat has been sitting under covered storage for roughly 10 years, only 292 hours total on the boat though.


still wasn't able to move the crank by hand and I don't have a special GM crank tool.....


Has anyone been in a similar situation and what do you guys use to move the crank? I'm a BMW technician so I'm familiar with motors in general, just fairly new to marine motors and the GM 4.3.

Your 92 bayliner most likely was sitting because the hull probably had rot issues. Bayliners of that era were not know for build quality

292 hours doesnt matter it it was neglected, abused, and put away improperly

10 years is a long time, was it stored properly? Most likely it was parked with water in the block because there was a problem

Spend the $14 on a GM crank socket

Same steps to revive a sitting and neglected BMW apply to any other motor. Isolate the motor from the transmission, read the manuals, remove the motor, verify it turns over, and most importantly, rusty cylinder bores is bad

Pull the drive, then pull the motor and get it on a stand