1997 5.7L thunderbolt ignition. Slow crank

[nola mike]

Motor is toast

 

[findinghomer]

So toast?

 

[nola mike]

So toast?

No, that was for AD. But I've already given my suggestions.

 

[findinghomer]

No, that was for AD. But I've already given my suggestions.

Oh ok. Yeah the only thing I haven't done diagnostic wise, is turn it by hand, I don't really understand how to do it. I did try to turn the flywheel with a flat blade screwdriver when I had the starter off. It didn't seem like it wanted to budge , And I didn't know if it was supposed to be able to turn that way , so I just put the starter on

 

[findinghomer]

But if it's turning with the starter, ( although slowly) I would imagine I should be able to turn it by hand to some degree. Just don't really know what to be looking for or what to do if it's turning by hand, but kind of hard. It's obviously not completely seized up, It cranks at a steady slow pace, It's not an intermittent speed

Oh I did not do the battery jumper cable, test I'll do that tomorrow, I did pull the coil wire though to eliminate timing.

 

[alldodge]

New larger cables and removed the switch
3 new starters
Pull the drive, that's the only thing left, and if it still cranks slow it has to be the motor

 

[findinghomer]

New larger cables and removed the switch
3 new starters
Pull the drive, that's the only thing left, and if it still cranks slow it has to be the motor

Ok. So the boat is not worth a 10k+ motor replacement, I'm reading a 350 "yard block" and switching all my Marine parts onto it would work. I can pull the motor and put it back in, but how do I know exactly what to get? Like how do I know the motor mounts would be in the same place for example? Do I just match up the year and cylinder size? A 5.7L V8 Chevy from the same year?

 

[alldodge]

Pull the drive first

The 305 and 350 use the same block, only the years can bring about holes missing as in maybe a ALT or raw water pump bracket bolt hole won't be there. Motor mounts stay the same

 

[findinghomer]

Pull the drive first

The 305 and 350 use the same block, only the years can bring about holes missing as in maybe a ALT or raw water pump bracket bolt hole won't be there. Motor mounts stay the same

Yes I've already pulled the drive. The only thing I see that is concerning, is one of the two black o-rings is missing on the drive shaft is missing , and the orange one at the that goes into the engine coupler looks like it was stretched and maybe twisted, I don't know if that's just from pulling it off or if something happened

 

[alldodge]

ok, than it has to be inside the motor
If you pull the heads you should be able to rotate the crank by hand. If unable to rotate by hand it's bearings

 

[nola mike]

ok, than it has to be inside the motor
If you pull the heads you should be able to rotate the crank by hand. If unable to rotate by hand it's bearings

He still hasn't tried turning by hand.

 

[findinghomer]

He still hasn't tried turning by hand.

Yes i haven't. I googled how to do that, I see ppl removing the short bolts, and then putting long bolts in the harmonic balancer, to wedge a pry bar in between and crank it? If so , how do I know what bolt to put in there, take one of them out and take it to to a hardware store?

 

[alldodge]

With the plugs out grab the belt, you should be able to move it some

 

[nola mike]

Yes, or see if there are a couple of holes in the pulley and stick some smaller bolts, screwdrivers, whatever will fit in there. As mentioned you can also turn via the ps pump or alt. Shouldn't take much to turn with the plugs and out drive off.

 

[findinghomer]

With the plugs out grab the belt, you should be able to move it some

Nope it doesn't.

 

[alldodge]

Nope it doesn't.

spun a bearing, maybe a piston cracked

 

[nola mike]

spun a bearing, maybe a piston cracked

Could be sticking valves as well (less likely if you can't turn with plugs out) or seized ps pump/alt. I'd remove belts, check oil, pull valve covers. But agree that if you can't turn it by hand you've got problems

 

[findinghomer]

spun a bearing, maybe a piston cracked

Could be sticking valves as well (less likely if you can't turn with plugs out) or seized ps pump/alt. I'd remove belts, check oil, pull valve covers. But agree that if you can't turn it by hand you've got problems

Okay I really appreciate you guys helping me diagnose this, I was completely stumped, and since I don't know much about the guts of an engine I figured something was going on beyond my ability. I'm coming to terms that I likely need to replace the motor.. It's lasted me for 15 years and probably has well over a thousand hours on it so I guess it was bound to eventually happen.

Mike, When removing the valve covers what do I look for? I really don't know much about engines, Im just capable of pulling parts and replace parts, I do have the capability (and have pulled) this engine out of the boat before, But actually opening them up and working on them I've never done.

The cost for a marina to put even a used engine in it , is not worth the value of the boat, so I'm trying to see what options I have to DIY. I have a brother that works at a salvage yard and I could get a 350 truck motor , I just don't know what all that entails , ie. what would line up or need to be moved over , or exactly what would be compatible. Seems like that would be cost efficient and worth it for me to do, and I think I could pull it off lol

 

[nola mike]

You're looking to see that all the valves are opening/closing, no bent push rods, rockers in place. Turn engine by hand to feel for binding at a particular point, grinding etc. pulling a truck motor and swapping everything should be straight forward but usually a few speed bumps if the vintages are off. I don't know enough about year to year changes on the 350 to advise. I got my 4.3 from a junkyard Blazer for $180.

 

[findinghomer]

You're looking to see that all the valves are opening/closing, no bent push rods, rockers in place. Turn engine by hand to feel for binding at a particular point, grinding etc. pulling a truck motor and swapping everything should be straight forward but usually a few speed bumps if the vintages are off. I don't know enough about year to year changes on the 350 to advise. I got my 4.3 from a junkyard Blazer for $180.

It is a 1997, 5.7L V8 , 2bbl, 350 , 260hp. I think that's a small block? What exactly would I need to know from the donor engine if it will work? I know I can get the failed engine out and bolt on All of the mercruiser parts necessary to the donor engine, except for I'm reading it would need a marine camshaft? I don't know how to do that and not sure if that's something I could do if it means tearing the engine all the way down.