Current Merc 5.7 Cracked...Suggestions for Engine Replace Steps

[carrera205]

Fired up the Mercruiser Alpha 1 5.7L the end of last summer and got milkshake coming out of the dipstick... dammit there goes the block I think. Now I need to pull the engine and figure out what to do. I'm pretty mechanically proficient and have done two engine rebuilds for autos before (SBC350 and Ford400M engine). From those of you who have been down this road what are your suggestions? I have a few questions as well.

My thoughts were pull the engine and get it on a stand. Start the dissasembly and find out what went wrong and start to salvage whatever possible. I don't have $5K sitting around to replace it all but I could spend around $2-$2.5K.

Questions:

1. If the block is screwed what can I salvage? What damage should i be looking for in this situation?
2. If I get a fresh block where can I get the best rebuilt kit? Best source for new block?
3. What major differences should I be on the lookout for when doing a marine rebuild?

 

[Scott Danforth]

It helps to know a few more things

what vintage block? pre 1985? 1985-1995? 1996 or newer?

a couple of things can contribute to water contaminated oil:
bad risers/manifolds will leak water past the exhaust valves to the piston and slowly leak into the oil
bad intake gasket
bad oil cooler
cracket block or heads

first diagnose what is wrong, understand why it went wrong, then determine course of action.

if it is your block and/or heads and you want to save a few dollars and get back onto the water quickly, a truck block and heads from a good donar vehicle can be had from a u-pull-it type salvage yard such as LKQ for about $350. change the core plugs to brass, change the gaskets and you can be back on the water for $600

if you want a reman, check your local shops, or order from either Rappido or Michigan Motorz

if it is your manifolds, your motor may be fine.

again, it comes down to diagnosis of what has actually failed and why.

 

[tpenfield]

Yea, the key thing would be to do a pressure test on the cooling system and 'listen' for the air escaping BEFORE taking it apart. That will tell you where the crack(s) is/are. All to often we see folks tear into an engine hoping to find something obvious and they don't . . . might be as simple as a head gasket, but who knows at this point :noidea:

Is there a history of non-winterization that would explain the water in the oil?

Got any core plugs that pushed out of the block? or water dripping from the block/manifolds?

 

[Bt Doctur]

If your near exit 9 of the njtp you can have 2 5.7 short blocks for free.1 is an older 1 piece seal and 1 is a newer vortec motor that had some water in it from an overheat and is now a bit tight to turn.

 

[carrera205]

Thanks for all the replies! Scott Danforth it's an 1989 block. When I first opened it up last summer and figured this out I didn't see any water pooled under the engine and there were no freeze plugs that popped out.

tpenfield how could i do a pressure check on a raw water system? When I first attached the muffs and turned on the water i didn't see any leaks anywhere on the outside of the engine it didn't give me any clues until it started coming up out of the dipstick tube. At this point I sorta figured since I ran it with the oil/water mix all the oil galleys would be screwed with the oil/water mix unless there is a way to clean it out and get fresh oil in there.

Here's a pic after I freshened up the engine the last time when it had sat for a few years

 

[tpenfield]

Carrera,

Pressure testing on a raw water cooled engine is a bit more difficult, but can be done. Since you are getting water in the oil, you can exclude the exhaust manifolds for now. You would then have to block off the four hoses the lead to the exhaust manifold/elbows and then pressurize from the intake hose. About 10 psi should do it. You will want to drain all of the water from the engine block first.

 

[NHGuy]

Yup, use some of those hose pinchers and you isolate the block. Then slowly turn over the crank to actuate valves while you listen for hissing. If it froze it's likely in the valley under the intake manifold. If it's just water that got in the motor via the exhaust the block could be good.

If you end up getting a motor you save the intake, alternator, carb, electrics, ignition. Maybe the heads. If you want a deal on a drop in, there was a used but good stroked marine 350 on craigslist Massachusetts last week. 383 ci, $1800.

 

[carrera205]

Well the mystery is over it's dead... now the salvage begins. With just around 400 hours on the engine I'm thinking i can salvage a lot. I'm thinking of getting a new intake, carb (Holly), cam, and salvaging as much of everything else as possible. The heads I'll probably have redone just to get it fresh.

 

[Bondo]

With just around 400 hours on the engine I'm thinking i can salvage a lot. I'm thinking of getting a new intake, carb (Holly), cam, and salvaging as much of everything else as possible. The heads I'll probably have redone just to get it fresh.

Ayuh,.... I wouldn't trust those heads, they've been frozen,....

Get a new/ reman Long block crate motor with Vortec heads,....
Get yer new intake to match the heads,....
Get yer new carb, but Not a Holley,.... Merc used Quadra-jets, 'n then the Merc/ Weber Carter clone,....
An Edlebrock Preformer is an exact copy of the Merc/ Weber carb, so the linkages, 'n what-nots will fit perfectly,....

Other than the marine accessories on yer old motor, the rest of it is scrap,.....
It's a false economy to swap the internals of that motor, into another block, without full machine work to be sure it all matches,...

 

[sub2010ss]

Wow!! And I thought my block looked bad! I can't believe it didn't crack the outside as well. I just got done doing this to my old 305 and upgrading to a 350. I used rapido. The engine is doing great. I also swapped the 2 barrel carb and intake to an edelbrock aluminum intake and 4 barrel carb.