4.3L V6 Mercruiser Hydrolocked

[rodgeml1]

Engine: 4.3L V6 0F586331

After replacing the outdrive, I hooked the muffs up and tried to start the engine. The motor has been sitting for a couple of weeks since the last time out so it was slow to start. I got it to finally start but dropped the throttle too quick and it puttered out. By now, the battery had died so I put a charger on it and tried to start the boat again. I got the very telling "CLUNK" of a hydrolock.

I pulled all of the plugs in order to check and see if the motor itself was siezed and found A LOT of fluid in the #6 cylinder. I pulled all of the rest of the plugs, turned the motor to get the moisture out, sprayed some oil in the cylinders, replaced the plugs, and she started right up. I ran for around 10 minutes with muffs and she ran great. Shut it off and started back up with no problems. After doing this a few times, I finally got the "CLUNK" again. I checked the #6 cylinder and didn't find any fluid. I tried to crank it with the plug out of #6 and it wouldn't turn. I pulled the rest of the plugs one by one in order to determine which one would release enough pressure to allow the starter to turn the motor. This time, the problem cylinder was #2. I didn't see any fluid come out, but that was the only one that allowed the motor to turn.

I started the motor up with the #2 plug out and ran for a bit but didn't see any fluid coming out. And when I tried to start, there was still a slight clunk before it finally turned. I finally decided to kill the water and run for a little bit to dry out the cylinders and call it a day. I did check the engine oil after all of this. It was a pretty color with no milky characteristic to it at all.

So what do y'all think I'm looking at? Is a cracked head ruled out since I'm not seeing any water in the oil? Blown head gasket?

Thanks for the consideration guys.

 

[Fishermark]

Re: 4.3L V6 Mercruiser Hydrolocked

My first guess would be a bad / corroded manifold or riser.

 

[TilliamWe]

Re: 4.3L V6 Mercruiser Hydrolocked

My first guess would be a bad / corroded manifold or riser.

That's my 1st, second, third, and fourth guess also. Water in a marine engine is almost always exhaust manifold/riser related. Luckily, it's also the eaiest thing to check.

 

[rodgeml1]

Re: 4.3L V6 Mercruiser Hydrolocked



Great....thanks for the suggestion. I took the riser and manifold off the side I'm seeing water. I don't see anything glaring that would indicate the water is leaking through and down to the cylinder. What do y'all think?

 

[ericp501]

Re: 4.3L V6 Mercruiser Hydrolocked

check your starter bolts.. Make sure you didn't break one and now the starter is kicking out when you try to start it. Gives the same type of "clunk"

 

[makonnen]

Re: 4.3L V6 Mercruiser Hydrolocked

Its difficult to tell with the gaskets in place.

The manifold in the first two pics look pretty corroded.

Remember the rust rule: its way worse than it looks.

 

[rodgeml1]

Re: 4.3L V6 Mercruiser Hydrolocked

Ok I removed the gasket remnants from the riser and the manifold. There appeared to be three layers to the gasket. Is that typical for this gasket?

The faying surface of the manifold is in really good condition, but the same can't be said for the mating surface on the riser. One flange was particularly bad with an obviousl reduction in thickness. I also so daylight between the gasket and riser surface before I scraped the gasket off. Anyone know a good outlet to get a new riser? I don't see that I have another option here. I'm going to go ahead and pull the other riser off too. Might as well make sure it's in ok shape before I try to seal her all back up.

 

[TilliamWe]

Re: 4.3L V6 Mercruiser Hydrolocked

They sell risers here on iboats, and in just about every other marine catalogue. And you need em.

 

[joewithaboat]

Re: 4.3L V6 Mercruiser Hydrolocked

That riser is toast and the manifold needs to be surfaced. If not by a machine shop, at least with a file by hand.

 

[Fishermark]

Re: 4.3L V6 Mercruiser Hydrolocked

In addition to iboats, here is a site with good prices and service. It lists both 3" and 4" risers.

 

[makonnen]

Re: 4.3L V6 Mercruiser Hydrolocked

You are likely looking at the problem right here:



Imagine how much gasket is preventing water from entering the exhaust at this point.

(Note to self: check elbows, risers and manifolds this week)

 

[rodgeml1]

Re: 4.3L V6 Mercruiser Hydrolocked

You are likely looking at the problem right here:

View attachment 147555

Imagine how much gasket is preventing water from entering the exhaust at this point.

(Note to self: check elbows, risers and manifolds this week)

Yep, that's exactly where I could see daylight between the gasket and the riser when I pulled it off. No way was I getting a good seal there.

Hilarious graphic by the way....gave me a good chuckle.

 

[makonnen]

Re: 4.3L V6 Mercruiser Hydrolocked



Its not a hard job, just labor intensive. Good luck!

 

[rodgeml1]

Re: 4.3L V6 Mercruiser Hydrolocked

Another question for y'all: These are pictures of my cleaned off manifolds. Should I try to salvage them or just replace them? There isn't much material between the water jacket and the exhaust port in some places.

 

[rodgeml1]

Re: 4.3L V6 Mercruiser Hydrolocked

New peculiarity that I'd like to get y'alls opinion on. I have both of my exhaust manifolds and risers off of the boat. I pulled all the plugs and turned the starter to blow out any residual moisture from the cylinders. The started turned strong with no problems. I replaced all the plugs and, without any water running into the boat, tried to turn it over. Same "CLUNK" as when I was originally hydrolocked. So I went through the same exercise of pulling the plugs, pumping the moisture out, replacing the plugs and trying again. Same result. Turns great with the plugs out (not a surprise) then locks up with the plugs in. I don't have any water running into the system and haven't for a few days. Everytime I removed the plugs and turned the starter I see fluid coming out of the exhaust ports though I'm figuring it's probably fuel. Do y'all have any clue from where that water might be coming?

 

[joewithaboat]

Re: 4.3L V6 Mercruiser Hydrolocked

Not sure about your continued presence of water...

Those manifolds are iffy at best, if you put them on like they are they will leak. Not sure what you did to surface them but they need to be very flat without the rounded edges. Buy new ones or let a machine shop surface them. Id replace them, they have a couple very narrow places on them with lots of pits.

Good luck!

 

[rodgeml1]

Re: 4.3L V6 Mercruiser Hydrolocked

Well....I found from where all of the metal pieces in my cooling system were coming. Yikes.

 

[rodgeml1]

Re: 4.3L V6 Mercruiser Hydrolocked

After persistant symptoms that I described in post #15, I decided to unplug the fuel pump and do a compression test on all cylinder. Unfortunately I wasn't able to get any good readings. The engine again locked up with all the plugs out and the compression tester in any of the cylinders. It still turns great with all the plugs removed and though I don't have any water running and the fuel pump unplugged, I'm still getting a mist of fluid out of the ports. I was thinking it might be a cracked head or blown head gasket, but that wouldn't be putting fluid into all cylinders (unless the head is cracked/gasket is blown on both sides).

Do y'all have any ideas as to what might be causing this have a suggested course of action?

 

[makonnen]

Re: 4.3L V6 Mercruiser Hydrolocked

Some things to consider:

- 4.3's will never win a consumer award for the quietest most fuel efficient engine. But they are solid engines. You're talking one big chunk of American-grade steel - iron head, block, manifolds. Its "not likely" that a head is cracked.

- 4.3's "rarely" suffer from head gasket failures. Again iront block, head and manifolds means similar expansion rates when the engine heats up. Think of the history of engines that have pattern gasket problems (manifold, head, oil pan), they are all aluminum head / manifold, iron block combinations.

- What does the oil look like?

- Catch the fluid coming out of the exhaust ports with a tissue paper. Is it water or fuel? I doubt its that much fuel coming out.

- Do a leak down test: buy a leakdown tester, you'll need a source of compressed air, turn each cylinder to TDC (the distributor rotor will be pointing to the spark plug for that cylinder hwen its at TDC), put in the compressed air, open the heat exchanger / rad cap and watch for bubbles in the cooling system. (I assume this is coolant cooled engine?)

- Make it happen again, when the starter gives you the big THUNK, put a socked and a ratchet on the crank pulley bolt head and turn the engine by hand, is it hard to turn?

And a little bit less likely:

- Could it be a starter problem? Remember the starter is in a pretty bad place, near the bottom of the bilge. Could the actuating mechanism of the starter be jamming?

- Could the engine / valve timing / ignition timing be WAY WAY off. In my youth, I've messed up valve / timing chain / ignition timing so bad that the starter would do some really weird things. One of them was the starter would get stuck like you describe. But I was literally just a kid trying to put together an engine without a clue.

Keep us posted and keep the pictures coming. Maybe a video if you can...

 

[halfmoa]

Re: 4.3L V6 Mercruiser Hydrolocked

Could the engine / valve timing / ignition timing be WAY WAY off. In my youth, I've messed up valve / timing chain / ignition timing so bad that the starter would do some really weird things. One of them was the starter would get stuck like you describe. But I was literally just a kid trying to put together an engine without a clue.

Keep us posted and keep the pictures coming. Maybe a video if you can...

^^^The 4.3 distributor will drop in at any angle, not just 0 degrees or 180 degrees like most SBC engines, this may be an issue.

Also, automotive 4.3s from the mid 90s are notorious for leaking coolant on the front left side from the area between the intake and head.

Of course this is all automotive engines, mid 90s Vortec plants so your mileage may vary...