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Reliability of a rebuild on a 350

millerjustin82

New member
So, I had some no start issues that turned into blown top end issues. The mechanic at the big marine shop in town mentioned that getting a rebuild, or having this one rebuilt would not really be a good idea due to poor reliability.......I'm in British Columbia, and the cost of a ready to run 5 litre was quoted at $9800 not including the cost to remove and install.......remember that's Canadian dollars, but again, my question is regarding the realiability regarding rebuilding the current 5.7 that's in the boat now?


As I would most likely make a winter project of it, the rebuild kit is only around 450 dollars for the full kit, I'd be able to do it for a bit more than that doing the work myself.
 
Rebuilt engines are 100% as reliable as new if rebuilt correctly, and 0% if done incorrectly. It's possible the guy meant there are no conscientious techs doing rebuilds in your area, but who knows what he meant without any context.

I'm often suspicious of techs that say things are "blown". It generally means they see broken parts but have little idea of the root cause, or what failed first and why.

Why does the bottom end need rebuilding? Maybe share what happenned and we might be able to shed light on what you might run into - maybe there's not much chance the block or crank are any good (in which case there's nothing to rebuild)
 
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millerjustin82, do not fear an over-hauled engine.
As said, if done correctly, you will be able to get years of good service from one.

However....... this is a SBC (small block Chevy) engine.
The factory GM full dished pistons should NEVER be used for a Marine application. This is the wrong piston for this build..... PERIOD!!!!!!!

If you are considering having one built, please read this thread begining at post #7.

http://www.marineengine.com/boat-forum/showthread.php?394668-V6-to-V8-engine-swap



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Thanks for the information, I'll make sure I'm fully versed in the do's and don'ts for this job, or I'll source out a reputable shop in the area hopefully.
 
Ok, so Looks like I might have a lead on a 400 SBC, which is rebuilt and drop in ready. After a bit of research it looks like the jury is out on whether or not it's a decent motor for marine use. Still looking into options for a 302 or 350, but anyone have any experience with the 400?
 
Ok, so Looks like I might have a lead on a 400 SBC, which is rebuilt and drop in ready. After a bit of research it looks like the jury is out on whether or not it's a decent motor for marine use. Still looking into options for a 302 or 350, but anyone have any experience with the 400?

The 400 cu in SBC engine has Siamese Cylinders...... meaning that no coolant is able to flow around/between each cylinder.
This inhibits the engine's ability to "dump" heat evenly around each cylinder, causing this to be a poor choice for a Marine application.

Note the "steam" holes that were added.

148_0504_how_12_z.jpg
 
Not knowing what boat this is in, I'll make the sweeping generalization that 5.0L don't make good replacements for 5.7s . Boats need torque to move them, torque comes from displacement. For example for two 250 HP engines, one a 5.0 and the other a 5.7, the 5.0 "makes" its "horsepower" by outputting less torque, but revving higher compared to a 5.7.
 
It's a 25' Bayliner. It originially had the 5.0, then the old owner put in the 5.7, and now that that is shot I'm faced with what to put in it now. The marine shop I took it too seems hell bent on selling me a brand new 5.0, But there is a reputable engine repair shop that has this 400 sbc that is drop in ready for a great price.
 
......................

It's a 25' Bayliner.
Which year model?
Merc, OMC or Volvo Penta stern drive?

The marine shop I took it too seems hell bent on selling me a brand new 5.0,
Say NO to this silly and unproffessional advice!

But there is a reputable engine repair shop that has this 400 sbc that is drop in ready for a great price.
No shop that I know of would deliberately build a 400 cu in SBC for a Marine Cruiser application.
To do so would be an extremely poor choice, and it would make a HUGE statement about this shop's lack of knowledge regarding the SBC Engine.

Don't get me wrong...... the 400 specs (4.125" bore w/ a 3.750" stroke) would be excellent..... but the siamese cylinders don't cut the mustard!
 
It's a 1992 2452 Classic, it's got an Alpha one drive, I figured it was silly advice from the shop as they are just trying to sell a brand new engine. Again, I'm looking for a cost effective, yet still reliable solution
 
Looks like neither mechanic ( using the term loosely ) is giving good advise, I agree with Mr. Ricardo.
I'm only a wanna be boat mechanic with only a few < 10 full engine rebuilds under my belt..

5.0 / 305ci is newer GM - Just say NO ( 302 is Ford 5.0 and 302 is old GM 5.0 )
400ci - you will have cooling issues.. not good.

How "bad" is your current engine ?
 
Well I'm going to redo all the compression testing that this "shop" did. But their numbers are #1: 60psi #2: 100psi #3: 30 psi #4: 60 psi #5 40: psi #6: 50 psi #7: 50 psi #8: 40 psi.

So that's pretty rough, but I'm thinking I'm going to pull the heads here shortly and have a look, cause the boat ran decently last year according to the old timer I bought the boat from across the street. On a positive note, I may have a lead on a rebuilt 5.7 vortec, but I'm not sure if it's compatible with my boat
 
Before you remove the cylinder heads, give some thought to a cylinder "leak-down" test.
Once the heads have been removed, this is no longer an option!


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That's sort of where I was going to start my troubleshooting, I am really hoping it's leaky valves or something less invasive. I just need to get a few more tools and a leakdown tester.
 
I suppose, since i Know they are already leaking pretty badly, to find the source of the leak I don't really need the actual leak down tool ? Just put air to the cylinders and find out where it's going......Correct me if I'm wrong
 
RE: 5.0 in a 25ft boat.... Many manufacturers are guilty of putting the smallest (and cheapest) engine they can get away with into what I call "boat show specials". These boats are sold at a "price point" and often without sea trials. Many of these owners are dissatisfied with the resultant performance and spend time and money trying different props, trim tabs, lift fins on drives and often resort to "bigger carbs" and other performance enhancing bolt-ons. The last owner of your boat fixed the problem the correct way... more displacement. I agree 100% with Ricardo that while 400CID is a good solution to the displacement issue, getting it from a SBC is not the way to go. A friend of mine in the marina has a 25 ft boat of like layout as yours. He has a 454 with a BRAVO 2 drive. Not a speed demon but it moves nicely with company on board.
 
Thanks for the Info Sandkicker. I've sorta written off the 400 just on research of the overheating issues. If this one is toast......which it likely is but I'm holding out hope that is something small....I'm going to replace it with the rebuilt vortec assuming it drops in without issue. Failing that I'll pull this one and just have it rebuilt and leave the boat sit for the crappy cold season.
 
Well.. there's a few differences with the Vortec..and depending on where it came from, could be a better/closer fit.

If you can do a leak down test.. great.. hopefully the cylinders are scored to bad.. and it's just a gasket and head problem.
 
I've been informed that the motor will go in just fine, but it's a matter of mating with the leg on the boat. So I'm waiting to hear back on that one. Until that point, yup, leak down test with fingers crossed it's just the heads. Cause that's not a huge deal.
 
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