Is my engine shot? Low compression, Mercruiser 3.0

[ronaldreagan]

My 2003 Mercruisrer 3.0 (4 cyl.) would crank but not run. I checked the for spark, fuel, and compression. It's getting fuel and spark. The cylinder compression reads 70psi (cyl 1), 45psi (cyl 2), 30psi (cyl 3), 50psi (cyl 4).

I pulled the manifold and this is what I found, see picture. I plan to pull the head although the engine is not seized, I want to see how bad the cylinders are rusted.

Is my engine shot? Any suggestions on next steps (besides buy a new engine...)

 

[tpenfield]

As Ronnie would say . . ."Well, there you go again"

It is 'shot', as in needing some rebuild action. You'll know more when you pull the head off.

 

[Bondo]

I plan to pull the head although the engine is not seized, I want to see how bad the cylinders are rusted.

Is my engine shot? Any suggestions on next steps (besides buy a new engine...)

Ayuh,..... If you pressurize each cylinder at it's Tdc with compressed air,.....

You can "Hear" where the problem is,......
If the intake valve, you'll hear the air in the intake runner,....
Ditto the exhaust valves,.....
If it's bad rings, you'll hear it from the oil galleys,.....

If there's no freeze cracks, the block, 'n head can be rebuilt with machine work, 'n fresh parts,......
A new/ reman long block just might be cheaper though,.....
Depends on how well yer local Machinist likes you,......

 

[ronaldreagan]

more pictures.... valves and cylinders. The pistons and cylinder walls look a lot better than I expected, the valves look a lot more rusted than I thought. Anybody see a smoking gun for the low compression and recommendations for the next step?

 

[Bondo]

and recommendations for the next step?

Ayuh,...... Find yerself a machinist, if you expect that motor to run again,......

 

[ronaldreagan]

Ayuh,...... Find yerself a machinist, if you expect that motor to run again,......

Can you elaborate? I would be thrilled to get away with just rebuilding the head. Does the block need to be serviced too?

 

[Scott Danforth]

Take motor out. Take whole thing to machine shop. It needs a full rebuild. Or buy a different motor

 

[Scott Danforth]

let me elaborate a bit more. the white stuff on top of each piston is corrosion from water in each cylinder

the rusted cylinder heads is from water in each cylinder

that motor either was left outside for years with the spark plugs open, or it suffered a serious issue such as a submersion.

if the motor was submerged, it sat for a while with water in the cylinders

machining prices will be in the $500-700 range for a basic rebuild, however the rebuild kit will be between $500 and $900 depending on the condition of your crank

a running 3.0 is only a few hundred. (less if it has a rotten boat attached to it)

 

[fishrdan]

Is this a crack in the block?

I'd test the manifold by filling it with acetone, see if it has any external or internal leaks, shine a flash light up into the ports to see if there is any acetone leaking through.

 

[ronaldreagan]

pictures of head.

 

[Scott Danforth]

Still needs a full rebuild

 

[Bondo]

Is this a crack in the block?

I'd test the manifold by filling it with acetone, see if it has any external or internal leaks, shine a flash light up into the ports to see if there is any acetone leaking through.

Ayuh,..... Appears to be,.....

 

[ronaldreagan]

I finally purchased an engine hoist and pulled the engine. Disasembled it down to removing the pistons expecting to find the cause of my low compression. No visual sign of failure anywhere..... it actually looked really good which is not good since I'm trying to find the cause of the low compression.

- the rods are not bent.
- no internal cracks in the block
- no marks on the cyclinder walls
- the rings are intact

What else should I look for?

One thing I notice but don't know if it's a concern is when I turn the fly wheel without the head on it requires some force but can be done with one hand...

I called a couple machine shops, they want $5,000 to rebuild it and are backed up for 6 months. Not a cost effective option.

Any advice or help is greatly appreciated.

 

[Scott Danforth]

you know you have two threads going on the same topic

https://forums.iboats.com/forum/eng...ing-over-low-compression-mercruiser-3-0/page4

 

[ronaldreagan]

you know you have two threads going on the same topic

https://forums.iboats.com/forum/eng...ing-over-low-compression-mercruiser-3-0/page4

Yes, i tried to delete my post from today after realizing I replied to the wrong one. I wasn't able to...

All other readers, please see thread at https://forums.iboats.com/forum/engi...iser-3-0/page4