BrokenYugo MegaDork
8/12/17 8:51 p.m.

In one corner we have a Mercury Marine Mercruiser 4.3 (basically a Vortec head Chevy 4.3 V6 truck engine with a 2 barrel carb and water cooled marine exhaust) of 1997 vintage, myself, and my father.

In the other corner we have old man winter, mother nature, and the previous owner.

The fight so far: The gang really jumped the poor 4.3, the PO didn't drain it and neglected to put a nut on the air cleaner/backfire arrestor at some point, old man winter froze the block and kicked out one core ("freeze") plug on either side of the block, and then mother nature dripped water down the air cleaner stud for as many as 8 years.

I tried to free it up with a wrench on the crank bolt but just broke the bolt loose (yes, I tightened it back down), then sprayed a E36 M3load of penetrating oil down the carb a few days ago and today pulled the plugs and sprayed into all the cylinders. Then put a battery in it, said berkeley it and kit the key a few times, clunk, clunk, clunk and it spun a little! Clunk, clunk, engine now spins! Three cylinders shot out orange penetrating oil.

Put the water hose on it, reinstalled the spark plugs, poured some fuel into the carb bowl (gas gauge reads empty) and tried the starter, a bit of fiddling with the throttle (I think I flooded it, more gas went down the carb than into the bowl vent) and it roared to life briefly. Put some more gas in the bowl with more accuracy and it started on a few cylinders for a second and then seemed to be hitting on all 6 and settled into a decent enough idle for a minute, oil pressure read 20 lbs, which probably isn't that bad considering the oil is who knows what mixed with a non negligible amount of PB blaster and water. I didn't want to run it long with most of the water dumping out the block rather than the manifolds.

Now we're going to go at it with an inspection camera and see if we can find any cracks, pound some freeze plugs in, maybe change the oil (which doesn't look like a milkshake, yet) and see what happens. This was a free boat with a so so hull (some floor rot) so if the motor only needs a couple core plugs it should make for a cheap beater.

Any bets?

drainoil HalfDork
8/12/17 9:26 p.m.

I can only offer that JB Weld does indeed take care of small cracks in the block of a marine Chevy v8. It held for the two summers I ran it in my old Glastron-Carlson.

You may get good vibes running it on a garden hose but the real test will be in the water in gear and under load.

rustyvw Dork
8/12/17 9:48 p.m.

I bet it's fine, just put new freeze plugs in and change the oil.

Trackmouse SuperDork
8/12/17 10:02 p.m.

Fill it with ATF. Give it a week. Slap it together an run till grenades. Repeat next week.

oldopelguy UltraDork
8/12/17 10:06 p.m.

Even cracked isn't the end of the world if you have access for a drill and access to some brass screws.

BrokenYugo MegaDork
8/12/17 10:23 p.m.

I figure any minor external cracks won't be a big deal, non pressurized raw water cooling system and all means it wouldn't do much more than drip, the bilge pump works (or at least makes noise). My big concerns are a cracked block in the valley and cracked exhaust manifolds (though I would think the outside of them would crack first).

I did find a old school "Topsider" oil extractor in the garage that seems to still draw a vacuum, so that's covered if things get that far.

And yeah, I'm well versed in the "runs fine on the stand but sucks in the water" problem/scam. This was somebodies tube puller (even included the tubes) until something went wrong with the power trim (acts like it's the switch or a solenoid, goes down but not up) and he bought a new one, so I'm guessing the engine was reasonably strong when parked.

GTXVette Dork
8/13/17 6:42 a.m.

reading that made me remember Oh Crap I need that for my Boat,'Cause last Spring I was Given A Cool 14' Speedboat( Python) with no Motor. It's for an Outboard But I was Thinking Engine up Front and V-Drive

GTXVette Dork
8/13/17 6:52 a.m.

Oh yea, Pull a compression test, reading that should tell a lot.Fixing Cracks in the block are easy compaired to the heads, and like OOG said,Drill and plug the cracks if it's a perminent repair JB Weld if you are in a hurry.

bludroptop UltraDork
8/13/17 7:05 a.m.

Car engine dies = coast to the side of the road

Airplane engine dies = die in flaming crash

Boat engine dies = somewhere in between...

I've spent enough time on the water to insist upon 100% confidence in the equipment. But I've also had an engine quit in a narrow channel with a swift current.

Toyman01 MegaDork
8/13/17 7:14 a.m.

The engine may or may not survive, if the starter turned it, I'd say it will survive. If not, 4.3s are pretty cheap at the junk yard.

Cracked and rusted exhaust manifolds and risers will destroy a engine in short order. They are above the valves and will drain water back into the cylinders. If you plan to keep it alive at all, I'd inspect them closely and plan on replacing them if they look questionable. MerCruiser manifolds are notoriously thin and have a life expectancy of about 3-5 year in saltwater. Much longer in fresh though.

If it's been sitting for a long time, change the water pump and gear oil in the drive, and then pull the drive and grease the u-joints. While you have it out, check the bellows and shift boot for cracks. Lack of maintenance in these areas can get expensive quickly. These are pretty cheap insurance.

Stay close to shore for the first couple of outing. And keep in mind, paddling a large boat sucks.

GameboyRMH MegaDork
8/13/17 7:26 a.m.

Put some MMO or ATF down the plug holes to be sure no rings are stuck. Replace freeze plugs, change oil and add in 1qt of ATF, then run it.

Appleseed MegaDork
8/13/17 9:00 a.m.

It's a Chevy. It thrives on abuse. It will run like crap longer than most engines run at all.

drainoil HalfDork
8/13/17 12:14 p.m.
GameboyRMH wrote: Put some MMO or ATF down the plug holes to be sure no rings are stuck. Replace freeze plugs, change oil and add in 1qt of ATF, then run it.

Have heard farmers in years gone by would use diesel fuel (the old blends of course) for this. Not sure if it really ever worked though.

BrokenYugo MegaDork
9/9/17 6:15 p.m.

Finally got around to popping the manifolds off to check those, starboard/right side is good, just carbon in the ports, port/left side is pretty nasty, either the head or the manifold is trash (probably the manifold), not good. There is however a nearby craigslist ad for 2 rights and a left off an older OMC 4.3 that look to be about the right shape for the exhaust hose to hook up, we might pursue that. 

iceracer UltimaDork
9/10/17 4:18 p.m.

I'd be concerned how much standing water might have rusted the cylinder walls.   then again it would probably just be surface rust.

wearymicrobe UberDork
9/10/17 4:52 p.m.

Depends on if it was run in salt water before shut down. Frankly you can make those things run forever at low RPM even with 1 of the cylinders not firing and a valve stuck in another.

BrokenYugo MegaDork
9/10/17 5:51 p.m.

Weary, this boat spent it's entire life on one lake in MI, the only salt it's ever been near is road salt. 

Filling the bad manifold with water shows a very slow leak. Can't find an affordable used one (closest thing is a set off an older OMC 4.3, 120 miles away). Thinking we might try slapping it together and remember to drain them on shutdown, at least until the block proves to not leak water into the crankcase. 

wearymicrobe UberDork
9/10/17 6:50 p.m.

It will be fine. Like 75% sure then.

BrokenYugo MegaDork
10/23/17 4:50 p.m.

Finally got around to pounding some freeze plugs in it, managed to carefully install the one under the mount plate using a prybar. Ran it for a few minutes (long enough to get the block warm) on the hose on fuel poured into the bowl vent (seem it's currently out of gas, electric fuel pump sounds ok), it didn't milkshake the oil and showed 40 lbs on the gauge (seems to be where the oil relief valve comes in) by like 2000. So I think we're good to go after changing the oil, patching the floor and putting tires on the trailer. 

Our Preferred Partners