Merc 350, to rebuild or replace?

[acex008]

I just picked up a 1995 Chaparral 2130 SS with the 5.7L Merc/Alpha to rebuild. The previous owner didn't winterize it and when he took it out on the lake it hydrolocked, not surprisingly. He pulled a head off to find one broken piston top and then quit disassembly. Now I have it and torn down the motor to find that all the other pistons are in excellent condition including the rods (straight) and all the bearings look good. There was no evidence of water in the oil (not milky). Since he had pulled off one head, it's hard for me to determine if it was a head gasket on that side that made it lock up. The other head that I had pulled off was in excellent condition including the gasket.

I'm wondering if the block is fine and I just need to investigate the head, intake and exhaust for cracks. I will have the block, head and intake magnafluxed to be sure.. Or should I just pick up a reman motor and junk this one?

 

[funk6294]

Its hard to say. I would price out what a shop would charge you to do all of the work. In most of the rebuilds I have done the cost difference between buying a reman (or in some cases a new crate) were negligable. Despite the cost I still end up building my own often, mainly because I enjoy the work and take satisfaction in doing the work myself. That decision is all your own.

Btw, I thought you had a line on a vortec replacement? Why not go that route? It would eliminate any questions on condition. Sell off parts from the old one.

 

[Rick Stephens]

Had the same problem with a V6 I bought last year. Once taken apart there is no way to know for sure and for certain. We magnafluxed and went ahead and rebored it. I lucked out.

There are common places for cracks to form on a SBC. Most machine shops know right where to look. If you do not have to rebore the engine, which is where more of the dollars start piling up as you buy rings, pistons, gaskets and pump and so on, then go for it. New piston for one hole, hone and re-ring the whole motor, have them go through the heads and check valve seats. Put er together and take your shot that it doesn't have a crack anywhere. A crap shoot, yeah. But same one buying a used block somewhere else.

Oh, and really carefully inspect the exhaust!

 

[acex008]

I bought this boat for $500 knowing I was going to replace the engine so I bought a Vortec (no heads or intake) from my neighbor for $200.

I just spoke with the original owner again and he had fogged the cylinders and did get some antifreeze in the block but hadn't filled it up (ran out of antifreeze and forgot to go back to top it off). When he went to use it the following season, it hydrolocked on him. When he pulled off the cylinder head he found that the #7 piston was broken. He assumed a cracked block and gave up. He's not very mechanical but can turn wrenches... It's sat in his garage for 5 years now, untouched.

Now that I have the marine motor apart and find that the oil shows no signs of water, the rod bearings look great, all the pistons are good except for #7, and the heads appear good, should I just rebuild it myself and sell the Vortec I bought from my neighbor to recoup some cost? I'm assuming that its either a blown head gasket, bad exhaust or exhaust gasket or a cracked intake manifold. Obviously I need to find the cause of the water in #7. What other cause would make for water in a cylinder? Since there's no water in the oil, I'm assuming the block isn't cracked. I would have the block, heads and intake check for cracks at my local machine shop before I proceeded to rebuild it... If there are no evidence of cracks I would have them wash the block, put in new cam bearings and then I'd rebuild it myself.

If I were to use the Vortec I bought, it doesn't have the hole drilled for a mech. fuel pump so I would need to go electric. Also, the timing cover is completely different (larger and plastic) as compared to the metal, smaller one on my marine motor. It's also a roller lifter motor... Will the marine heads (solid lifter) work with the non-marine Vortec with the roller lifters? I don't have the Vortec heads... The Vortec was pulled from a truck with 120k miles.

I'm just trying to weigh my options here.

 

[Rick Stephens]

You'd have to swap cam and pushrods over to the new block and install an electric pump. You would want to acquire an after market metal timing chain cover. And don't forget the pan is totally different on a Vortec. I'm guessing your '95 does not have a balance shaft?

If I was going the newer motor I would consider finding a set of Vortec heads and going the whole route. Tough call as you are making up a morphadite bastard child motor by mixing and matching. No such thing as a complete gasket set mixed that way, half will be Vortec set and half pre-Vortec. Your list making it a full vortec gets pretty long with intake manifold, electric fuel pump system, timing cover, roller lifters and rods and.....

 

[acex008]

Ugh, you're right. I was trying to go over the differences in my head and missed some of those. At this point, my neighbor is going to take back the Vortec and I'm going to bring my marine block, heads and intake over to the machine shop to check for cracks. Tonight I'm going to inspect the exhaust system as well. I'm hoping I can find an obvious issue so that I can just rebuild my marine motor and be done with it.

As for bastard motors, my dad and I call them grenades! We've built quite a few over the years taking the best parts from various motors to make one good running engine. For some reason they've all run stronger and better than other motors we've done. Maybe a placebo effect?

 

[acex008]

If the block was cracked, wouldn't there be evidence of water in the oil? Since it was just in the combustion chamber, doesn't that mean only the top portion (not the block) is at fault? I will still have the block checked but I'm assuming since the rotating assembly looks good without milky oil, the block is fine... Or am I wishful thinking?

 

[Rick Stephens]

It hydrolocked without water in the pan. Less likely the block than the exhaust or a head. Most likely the exhaust. But that's a WAG. Cracked exhaust could/would fill whatever cylinder had exhaust valve open.

 

[acex008]

Agreed. My last boat had a bad manifold-elbow gasket and did the same thing. But much worse with multiple broken pistons, yet good oil. I rebuilt it (new pistons, rings, bearings, reseated the valves, gasket set, etc.) and it ran super strong with no issues. Fingers crossed this motor will do the same. At least this time I'll have the block checked for cracks first.

 

[funk6294]

I bought this boat for $500 knowing I was going to replace the engine so I bought a Vortec (no heads or intake) from my neighbor for $200.

I just spoke with the original owner again and he had fogged the cylinders and did get some antifreeze in the block but hadn't filled it up (ran out of antifreeze and forgot to go back to top it off). When he went to use it the following season, it hydrolocked on him. When he pulled off the cylinder head he found that the #7 piston was broken. He assumed a cracked block and gave up. He's not very mechanical but can turn wrenches... It's sat in his garage for 5 years now, untouched.

Now that I have the marine motor apart and find that the oil shows no signs of water, the rod bearings look great, all the pistons are good except for #7, and the heads appear good, should I just rebuild it myself and sell the Vortec I bought from my neighbor to recoup some cost? I'm assuming that its either a blown head gasket, bad exhaust or exhaust gasket or a cracked intake manifold. Obviously I need to find the cause of the water in #7. What other cause would make for water in a cylinder? Since there's no water in the oil, I'm assuming the block isn't cracked. I would have the block, heads and intake check for cracks at my local machine shop before I proceeded to rebuild it... If there are no evidence of cracks I would have them wash the block, put in new cam bearings and then I'd rebuild it myself.

If I were to use the Vortec I bought, it doesn't have the hole drilled for a mech. fuel pump so I would need to go electric. Also, the timing cover is completely different (larger and plastic) as compared to the metal, smaller one on my marine motor. It's also a roller lifter motor... Will the marine heads (solid lifter) work with the non-marine Vortec with the roller lifters? I don't have the Vortec heads... The Vortec was pulled from a truck with 120k miles.

I'm just trying to weigh my options here.

Ah, I didn't realize the vortec you bought was the lower end only. No heads. It's usable with you current heads, but as you noted it not complete and you would have to do an electric fuel pump on top of that. At 120k on the motor and still having to reuse your heads I would be looking at other options.

At this point I think you have a solid plan to have the machine shop inspect for cracks and use that to guide your project. If it's trashed then just go for a reman or crate. Who know you might get lucky.

 

[NHGuy]

I'd fix that engine myself too.
But be sure to find and eliminate how the water got into #7. Probably exhaust. It's always the exhaust.
If there was water in the block they freeze crack about 80% of the way up the side of the valley near the center.

 

[acex008]

Dropped off the block, heads and crank at my machine shop. They're going to check for cracks and get back to me. They don't think the block is compremised given how the oil looks good and how the top of the piston is broken. It actually looks like the ring gap was wrong during the first time it was rebuilt and it tore off some chunks along the top of the piston only, but the very top is washed off indicating water intrusion. I'm thinking exhaust too. I haven't inspected the manifolds yet but my last Merc 350 did the same thing and it was the square gasket between the manifold and the elbow.

 

[Scott Danforth]

I bought this boat for $500 knowing I was going to replace the engine so I bought a Vortec (no heads or intake) from my neighborfor $200.

Without the vortec heads, it's not a vortec. Its simply an SBC. You need the 96 and later vortec heads to get the benefit