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Boat People - Marine engines

Whistlepig

Member
Joined
Jan 13, 2021
Member Number
3363
Messages
19
Loc
Northeast LA.
I bought a boat (bust out another thousand) and it has a cracked block from not being winterized. Where is the best place to buy marine short blocks these days? Engine is a mercruiser magnum vortec 5.7.
 
sicumminsde said:
I thought it was just a sbc block. Any junkyard will have one or a thousand. I think there are minor differences but the actual block is the same? I may be wrong though
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You would think but most of the ones around here went to the scrapyards. Finding a shop to do the machine work in a reasonable time is also an issue. Everything seems to be LS these days
 
Whistlepig said:
You would think but most of the ones around here went to the scrapyards. Finding a shop to do the machine work in a reasonable time is also an issue. Everything seems to be LS these days
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makes sense. I guess I'm old school because I still own 3 vehicles (that I still drive) with a SBC.
 
BigBurt said:
Idk about a Chevy but on the Ford 351 versions the boat motor is reverse rotation
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Reverse rotation pretty much only (I.e I bet there’s an exception or two) shows up in twin inboards and ancient twin stern drives where you need one prop to go the other way. All stern drives made in the last 40 (probably 50 but I’m hedging my bets) accomplish this with gears. Not sure if newer inboards do the same as I’ve never worked on new twin screw stuff.

For an engine installed in the boat just hit the starter and observe the damper.
 
Steve300xcw said:
what is different on a block. marine vrs everything else?
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Sometimes nothing. Sometimes basically everything except the block itself is different.

But a lot of the time “different” just means that it’s a combo of stock parts that never existed in a road application.
 
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Buy an l31 crate engine from summit or wherever. It’s basically a truck vortec 350. I did this exact thing in my boat. The engines merc put in boats literally came off the same line as truck engines. Only difference is brass freeze plugs. My boat scoots with it. If you aren’t happy with it. Put a different cam in it and let her rip.
Edit..dayum! I paid two grand for mine. Price has doubled since then.:eek:
 
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Yeah prices are high! Was hoping to get a good short block but most I have looked at as far as rebuilt have terrible reviews.
 
Steve300xcw said:
what is different on a block. marine vrs everything else?
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I believe you could get mercruiser blocks with plated water passages for salt water resistance.

But I know a few guys that have just dropped generic SBC into their boats with no issues.
 
Chevy_man said:
I believe you could get mercruiser blocks with plated water passages for salt water resistance.

But I know a few guys that have just dropped generic SBC into their boats with no issues.
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I thought salt water engines had closed cooling systems? I don't see how one could plate just the water passages without plating the entire engine.
 
1oddtech said:
I thought salt water engines had closed cooling systems? I don't see how one could plate just the water passages without plating the entire engine.
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Electroplate with solution in the passages? Wouldn't be hard to have a few fixture plates to circulate solution instead of just dipping the block.

Just remember seeing some advertised years ago. Now I'm curious and I'm off to see if I can find what I vaguely remember. :homer:
 
I'm pretty sure that boat engine heads have stainless steel valves, which shouldn't be a concern if you get a short block. The last two gm crate engines I bought had stainless steel freeze plugs.
 
1oddtech said:
I thought salt water engines had closed cooling systems? I don't see how one could plate just the water passages without plating the entire engine.
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Nobody is plating cooling systems. Anything "plated" wouldn't last for shit with salt water sitting in it. Even hot dip galv doesn't do great.

Separate cooling systems are typical though. You have coolant circulating in the engine and exhaust manifold and instead of a radiator you have a big heat exchanger. Then there's a raw water system pumping seawater through the heat exchanger and and into the exhaust via the exhaust riser.
 
pretty much an L31 engine. Different cam though. Michigan Motorz, Eagle Engines. Marine Engine depot. Flagship Marine. Yea, they are proud of their stuff. The days of $2500 long block are gone. Mercruiser retail on a new long block is $9300
 
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Seriously LS swap it

 
spareparts said:
pretty much an L31 engine. Different cam though. Michigan Motorz, Eagle Engines. Marine Engine depot. Flagship Marine. Yea, they are proud of their stuff. The days of $2500 long block are gone. Mercruiser retail on a new long block is $9300
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I looked at most of those but the reviews are all not that good. Mainly looking for somewhere someone on here has used that has a decent quality product.
 
From my limited understanding if you’re only running freshwater then virtually identical. If you’re running saltwater then they can be different for corrosion purposes in the cooling system.
 
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