5.7 Gm mercruiser coolant issue

[Eastboundndown]

Hello All. I am trying to figure out if a the engine block in a boat I recently purchased is done or not. Boat was not winterized when I picked it up but no exterior cracks to block, manifolds, risers are visible. I was told that the risers/ manifolds were bad and caused water to get into crankcase. I started by draining oil, then removed plugs, belts and outdrive and tried hand turning engine with no success. I then figured it might be pretty rusty in there so I removed intake and heads and am soaking block in mystery oil. I was told that when previous owner noticed water in oil he connected water hose to intake port on T Stat housing and test ran motor and then checked oil and found no water.. this leading him to believe that it was a manifold issue and not a block issue. I don’t believe this would rule out a leak head gasket or crack in head(s). Am I wrong? And I’m looking for suggestions on where to go from here. Thanks in advance!

 

[alldodge]

You have the heads off and it still will not turn over by hand.
I fthis is the case, its rebuild or replacement time

 

[Scott Danforth]

if the manifolds were frozen and cracked due to lack of winterization, the block, heads and intake are junk too.

you are looking at a new bobtail or at a minimum, a new long block, new exhaust manifolds, elbows, new intake, and new water pump, and new power steering cooler.

 

[Eastboundndown]

Thx for the replies, I haven’t tried to turn the crank by hand after I removed intake and heads. I removed plugs and belts and wouldn’t go so then removed top of engine and poured a bunch of mystery oil in there. I will have time tomorrow to work on it so I will know if it is seized or not then. Just wondering if since there are no visible block cracks or blown freeze plugs and although I don’t know exactly how long it’s been sitting....there was not a drop of water in the system when I picked it up so they may have drained everything out or it just dissipated. Is there a way to test block without pulling it out and sending to a machine shop or no?

 

[Eastboundndown]

If it comes down to a rebuild or replace Then what things should I consider in choosing the best option?

 

[alldodge]

Is there a way to test block without pulling it out and sending to a machine shop or no?

Could not rotate with heads on, and when heads removed, did not try to rotate. Get the crank to rotate and see if there is rust on the rings. If no rust on the rings then its on the bearings. If on the bearings/journals it needs rebuild/replace

If it comes down to a rebuild or replace Then what things should I consider in choosing the best option?

Depends on your wallet and hands on abilities. If you can rebuild a motor, then can get by with less dollars. If your going to get someone else to rebuild, then check prices and compare to rebuilt long block

 

[Bondo]

Ayuh,........ You have pulled the Drive,.. Right,..??..?? it's splined to the crankshaft ya know,.....

Since you pulled the top of the motor off, there's no pressure testin' it now,.....

What do the cylinders look like,..??

 

[Eastboundndown]

There was quite a bit of rust built up on top of block under intake manifold. The bolt on the crankshaft pulley snapped off when I tried to turn it. The piston heads and cylinder walls had some surface rust but cleaned up with some PB and wire brush so I tried to turn pulley with a strap wrench and still can’t move it.. I’m thinking I’ll continue disassembling engine and pull it out and see if it’s worth rebuilding, my guess is probably not. Not sure if the cost difference between having this block cleaned and machined would be much less then purchasing one already done and then there is still a good chance that heads may need to be replaced. I can repair or replace most things mechanical without too much trouble but I would have to do my homework and have a manual and obviously some additional guidance from all the helpful members of the forum to dive into a rebuild. I do have an engine stand, tools and good size well lit shed with heat & a/c.. It wouldn’t kill me to spend a few thousand on a rebuilt either though. Any opinions or input on pros and cons would be greatly appreciated.. thx

 

[Bt Doctur]

The bolt on the crankshaft pulley snapped off when I tried to turn it.
Yep, will happen every time on a seized engine and most times on a good engine.You have learned never to do that again.
In most cases where moisture has settled in a block and produced rust in the bores and rust inside the valley the block is most likely finished. PM me is your close to NJ.

 

[Eastboundndown]

The bolt on the crankshaft pulley snapped off when I tried to turn it.
Yep, will happen every time on a seized engine and most times on a good engine.You have learned never to do that again.
In most cases where moisture has settled in a block and produced rust in the bores and rust inside the valley the block is most likely finished. PM me is your close to NJ.

Thx, I figured as much. I appreciate you taking the time to respond. unfortunately I’m in MA. So not that close to NJ

 

[Scott Danforth]

NEVER EVER EVER try to turn a motor from the crank shaft bolt. ALWAYS use a crank socket.

even if the motor was free, you would need to rebuild it and may need to buy a new crank if the machine shop cant get the broken bolt out. however it sounds like you need either a new bobtail or the items listed in post #3

 

[Eastboundndown]

NEVER EVER EVER try to turn a motor from the crank shaft bolt. ALWAYS use a crank socket.

even if the motor was free, you would need to rebuild it and may need to buy a new crank if the machine shop cant get the broken bolt out. however it sounds like you need either a new bobtail or the items listed in post #3

Thx, didn’t know that I will have to pick one of up. Tough lesson to learn but a lesson learned never the less!

 

[Scott Danforth]

the bolt is intended to hold the balancer, and never designed to withstand the forces needed to turn the motor.