Catastrophic engine failure...

[Oshkosh1]

What else is there!
My son and I were out yesterday when I started loosing power. I immediately headed toward shore but ended up DIW about 1 mile from the landing. The engine gradually lost power until it just slowly died out. I popped the cover and the engine was REAL hot...although the water temp gauge never indicated any high temp. I was towed in, then allowed it to cool overnight.

Soooooo...I did a compression test. BAD...REAL BAD.

For reference...I did a CT about a month ago and had 135 across the board(dry).

Now...subtract 100psi. 35-40psi on Cyl 1-5, #6 was the "strong" one at a whopping 60#

Squirting a little oil did nothing to improve the numbers...

I had it running PERFECTLY on muffs just prior to taking it out. Purred like a kitten, not a stumble, hesitation...plenty of water flowing through etc...

Any help is appreciated.

 

[Grub54891]

Re: Catastrophic engine failure...

Sounds like the impeller went out,no water for the sender means no temp reading. Not sounding good right now.
Grub

 

[Don S]

Re: Catastrophic engine failure...

And all it takes is one plastic bag in the water and no water (or very little) gets to the pump or the engine.

You could spend time with a partial leakdown test to see if it's an intake or exhaust valve or a hole in the piston. I would just pull the head and have a look at this point. probably warped valves, or a hole in the pistons. Holes will be really obvious.

 

[RogersJetboat454]

Re: Catastrophic engine failure...

Leak down testing is next if you want to pinpoint where compression loss is coming from with out pulling the engine apart.

Regardless, she's going to need to be pulled apart, sounds like she got hurt bad.

 

[Oshkosh1]

Re: Catastrophic engine failure...

Luckily(whatever THAT is at this point)...the head is very accessable. I'm guessing I can pull it quickly. I'll do it when I have a little more time. Thanks for the responses.

 

[haulnazz15]

Re: Catastrophic engine failure...

If every cylinder had low compression like that, I'd say you blew the head gaskets. Could be some warping of the mating surfaces as well.

 

[Oshkosh1]

Re: Catastrophic engine failure...

"We" are still not on speaking terms yet...but I will tear into "her" within a week.

So....

Having never dealt with this sort of major internal engine issue I need some basic info.

When I remove the head, and IF there are no holes in the pistons...where do I start the autopsy?
How will I tell whether it's just a blown HG, or the head has been damaged?
What would be a fair price for a machine shop to rebuild the head if necessary?
While it's apart...any other work I should look to do?

What advice does anyone have regarding removal/reinstall?

Thanks in advance...any, and I mean A-N-Y advice from some of you old "salts" is appreciated.

 

[RogersJetboat454]

Re: Catastrophic engine failure...

When I remove the head, and IF there are no holes in the pistons...where do I start the autopsy?
How will I tell whether it's just a blown HG, or the head has been damaged?

Carefully remove the head gasket from the block, and check for burn marks, and missing pieces between the cylinders.

If none are found, flip the head over, and look at the valves, especially the exhaust valves (they get hotter than intake valves). See if the valves look perfectly round, or if it look someone took a file to them, and flattened sections out (burnt valves).

If no burning is apparent, you can also lay the head on a bench with the valves facing up, and fill up the combustion chambers on the head with something like WD-40 or any sort of thin fluid (your gunna want the spark plugs installed for this). Keep an eye on the fluid level. If it drops down, chances are a valve isn't seating properly, or there is a crack.

Check the condition of the cylinders. Any scoring on the sidewalls? Is there a ridge at the top of the cylinder about a 1/4 inch down? How do the edges of the pistons where they meet the cylinders look? Melting, or beaten up at all?

Chances are where you have such dismal compression figures, you're gunna see something with out having to look too hard.

What would be a fair price for a machine shop to rebuild the head if necessary?

It's all relative to the condition of the head you give them. Bare minimum, they will need to hot tank, and magnaflux the head for cracks. Any cracks found, and the head will need to be replaced. They will need to check the condition of the valve guides, valve springs, and valves them selves. Anything out of spec will need to be replaced. After that, 3 angle valve job, new valve seals. When I had my 6 cylinder head done it was about $400. That machine shop was a bit pricey, but they do excellent work.

 

[Oshkosh1]

Re: Catastrophic engine failure...

Thanks for the suggestions...

A friend of mine also said that the oil rings may have scored the cylinders...and in that case, if I see any marks in the cylinder walls I'll assume the engine is basically a paperweight?

 

[Dawg'sLife93]

Re: Catastrophic engine failure...

Thanks for the suggestions...

A friend of mine also said that the oil rings may have scored the cylinders...and in that case, if I see any marks in the cylinder walls I'll assume the engine is basically a paperweight?

You can have your block bored out over stock, then buy new oversized pistons, a rebuilt kit and rebuild it. That way you know what you have vs a used 35-40 year old engine, but 250's are fairly cheap to buy used.

IMHO, I would do both. I would buy a used engine, install it, then rebuild yous as you the time and extra cash. When next season gets here, you'll have new power.

 

[Oshkosh1]

Re: Catastrophic engine failure...

Well "we" had a talk...
I pulled the head off.
Now...I'm not a seasoned diagostician, so I'm not sure how to interpet the results.
I'm posting some pictures of the block, head, and headgasket. Any interpetation, opinion, conjecture at this point would be helpful.
I threaded the plugs back into their holes and filled the valve crown with gas. Cyls 1-4 leaked out quickly. #5 & 6 leaked out much slower, with #6(also the cylinder with the "most"...60psi compression) leaking out the slowest.
Thanks in advance for the help...

 

[Oshkosh1]

Re: Catastrophic engine failure...

Couldn't post pics of the HG...here it is.



And as far as any "scoring" of the cylinders, I couldn't see anything that looked significant...

 

[04fxdwgi]

Re: Catastrophic engine failure...

Couldn't post pics of the HG...here it is.

View attachment 199244

And as far as any "scoring" of the cylinders, I couldn't see anything that looked significant...

If it were me, I would be gatting a straight edge and checking the head to see if it is nice flat. Nothing in those pics jumps right to say "here it is". Since the head is off, might as well send to shop for a valve job. They'll check eveything before doing the job and if bad, they'll tell you right off the bat.

 

[ricohman]

Re: Catastrophic engine failure...

Thanks for the suggestions...

A friend of mine also said that the oil rings may have scored the cylinders...and in that case, if I see any marks in the cylinder walls I'll assume the engine is basically a paperweight?

The compression rings will be far more likely to do damage in this cases than the oil rings.
Clean the head up and lay a straight edge on it. I bet its warped. But the head will need a rebuild anyway.

 

[Volphin]

Re: Catastrophic engine failure...

On image 1219 there is a fairly obvious crack from the water jacket on Cyl 5 to the combustion chamber with a water trail. That head may be toast. The shot of the entire block shows glazed cylinders and what could be a crack in #1, but hard to make out. It's time for a refresh.

 

[RogersJetboat454]

Re: Catastrophic engine failure...

Exhaust valves for some of the cylinders look like they got pretty toasty hot. No carbon on anything. Also looks like they've sunk pretty far into the head. Since this is an early 70's engine, chances are high it doesn't have hardened exhaust seats (for unleaded fuel) if it hasn't been recently rebuilt.

Is there any sort of ridge at the top of the cylinder bores? Feel for it with a finger nail.

I say send the head off to a machine shop, and let them check it out for warpage, and cracks. Reasonable warpage can be milled out. Also probably going to need hardened exhaust seats installed. If it isn't cracked, have the machine shop give you an estimate for what it would take to rebuild the head, soup to nuts, then do a little shopping to price out what another fresh head would cost. Rockauto is listing remaned heads for a 1970 pickup for a bit over $400 bucks if you don't send back a core.

 

[Oshkosh1]

Re: Catastrophic engine failure...

Is there any sort of ridge at the top of the cylinder bores? Feel for it with a finger nail.

Yes...
Sooooo...assuming that the "whole shootin' match" is "all blowed up"...what does it take to pull the rest of the block? It looks fairly simple, other than the fact I have no hoist, or engine stand to hold it. The PO made "custom" mounts for it...as it was a replacement...so I probably would be better served to keep the block with the new mounts already on it.

What else do I need to remove? Looks like I just pull the sterndrive, disconnect the electrical, pull the engine mounting bolts and lift it out. I know that's probably the simplified interpetation...but bear with me here. Rebuilding a snowmobile motor is the biggest engine I've actually completely torn down.

What am I looking at for weight of the remaining block? I have a high ceiling in my "big" garage where it's stored. Will my joists bear the weight if I get a chainhoist?

Thanks again...

 

[RogersJetboat454]

Re: Catastrophic engine failure...

Yes...
Sooooo...assuming that the "whole shootin' match" is "all blowed up"...what does it take to pull the rest of the block? It looks fairly simple, other than the fact I have no hoist, or engine stand to hold it. The PO made "custom" mounts for it...as it was a replacement...so I probably would be better served to keep the block with the new mounts already on it.

What else do I need to remove? Looks like I just pull the sterndrive, disconnect the electrical, pull the engine mounting bolts and lift it out. I know that's probably the simplified interpetation...but bear with me here. Rebuilding a snowmobile motor is the biggest engine I've actually completely torn down.

What am I looking at for weight of the remaining block? I have a high ceiling in my "big" garage where it's stored. Will my joists bear the weight if I get a chainhoist?

Thanks again...

Yep, shes worn out...

Pull the drive, electrical, fuel lines, and unbolt the mounts.
Rough guesstimate is probably around 350 lbs (give or take) for the short block with a flywheel attached.

Not an engineer, and haven't seen the inside of your garage, but may be able to rig something up if your able to spread the load across multiple roof stringers. Other than that, you could also build your self a nice gantry crane out of dimensional lumber for relatively short money like some of the other members have done here.

 

[Idlespeedonly]

Re: Catastrophic engine failure...

On image 1219 there is a fairly obvious crack from the water jacket on Cyl 5 to the combustion chamber with a water trail. That head may be toast. The shot of the entire block shows glazed cylinders and what could be a crack in #1, but hard to make out. It's time for a refresh.

I believe the head gasket is still on in pic 1219. In pic 1214 3rd from right, the cylinder wall looks like it has had water in it, and the first cylinder has to much oil in it. Also, the combustion chambers all look rusty.

 

[Volphin]

Re: Catastrophic engine failure...

I believe the head gasket is still on in pic 1219. In pic 1214 3rd from right, the cylinder wall looks like it has had water in it, and the first cylinder has to much oil in it. Also, the combustion chambers all look rusty.

Great point Idle. I really need to get more coffee in the am. LOL