4.3 mercruiser exhaust manifolds and cracked block

[Cfrank5547]

New boat owner this year. While it has been fun it’s been frustrating to say the least. I bought the boat back in May and after taking it out a couple times I found water in the oil. Boat is a 1997 Monterey 186 with a 4.3 vortec mercruiser.

So after finding oil in the water I disassembled engine hoping for a blown head gasket but I found a cracked block instead. Obviously realizing I had been lied to and boat was never wintwrized. Ordered a reman marine long block and installed it on June 5th. Also replaced intake at this time as well. Started new engine up and it ran great. Took it out several times after this checking my oil and level religiously. Probably put 15hrs on motor and then all of a sudden started getting water in oil again.

At this point I’m tired of messing with it and boat season is almost over so I took it to a marine shop to be looked at. Before taking it I did do a compression test and all looked normal except cylinder 2 had water on spark plug. After taking it to a shop they removed heads and they said that the cylinder wall on number 2 was cracked.

My question and concern is this something that probably happened from a faulty reman process? Only thing that wasn’t replaced when new motor was installed was exhaust manifolds. The block is being sent back for a warranty claim. My question is if my exhaust manifolds were bad wouldn’t water have shown up quickly after new motor was installed? Other question is if my manifolds were filling my cylinder up with water wouldn’t my motor hydro lock or wouldn’t it bend something before cracking the block? Only other information I have is my exhaust manifolds are the one piece batwing design and the shop told me they can’t test them.

I’m nervous that something could void my warranty. I’m already gonna be out a lot of money in labor I would hate to have to buy a second motor in 3 months. Any info would be appreciated. I can’t catch a break!

 

[Grub54891]

Usually the protocol when replacing a frozen block, is to test the manifolds, or better yet just replace them with new. Bad manifolds cause bad problems. Especially if they were froze.

 

[Cfrank5547]

Can the one piece manifolds be tested? And if so how? The shop told me you can’t. I have no idea if they are bad and I don’t think they do either.. I also ran it several hours before water ever showed up. Seems to me if manifolds were cracked it would have shown up quickly

 

[Scott06]

One piece manifolds are notorious for leaking water back into engine but I can't see that cracking a cylinder wall. Likely the reman started with a bad core. Where did u get the reman from? If u get stuck with it you can sleeve that bore , a pita to tear down but not a lot of dollars. Try the warranty from supplier first, if cylinder wall is cracked I can't see how they wouldn't honor warranty

 

[Cfrank5547]

ATK was where the engine came from. I don’t care if I have to replace the manifolds but I’m gonna be pretty upset if they don’t cover warranty. I just didn’t think that even with water on top of the cyclinder it would cause that without causing something else first like a hydro lock or just straight catastrophic failure.

 

[Rick Stephens]

Doesn't take much water to significantly change pressures in the cylinder..... however, that usually happens near TDC when it is just a little water. Hard to crack a cylinder wall with the piston up.

Batwings suck. Sorry you got bit, but they are bad news all by themselves.

I have heard some say ATK is decent. No personal experience with them. Don't get up in arms until they deny a claim.

Oh, and welcome to iBoats. If you are doing any of your own work, this is the place to keep up with things. There's a lot of things, like batwings, to learn.

Rick

 

[Cfrank5547]

Thanks for the info guys. I appreciate all the help. I will keep y’all updated after the claim. And I plan on replacing exhaust manifolds anyways cause I have heard several people say they suck. Like I said I did the first motor change out and wasn’t too bad but I’m tired of messing with it or I would have done it this time. Thanks again guys

 

[Lou C]

There are kits out there (Barr Marine makes one) that make it possible to change from the one piece manifold to the 2 piece units without changing the Y pipe. Anytime major engine work is done, the exhaust manifolds should be tested. And that shop that told you, that the bat wings can't be tested is wrong. I had the Batwings on my OMC rigged 4.3 for a long time, 3 sets to be exact (here in salt water we have to change every 5-7 years to be on the safe side). I used to take them off, prop them up level and fill with acetone (careful, flammable) and let them sit and hour or 2. If there was no dampness in the exhaust ports, they are not leaking. I never had water leaks into the engine with 3 sets of these. When I did a top end engine overhaul in 2017 (installed reman heads) the last set were on their 6th year. I did test them, and they passed but the outlets were getting pretty rusty. So I changed over to the 2 piece exhaust like those used on late model Volvo Penta 4.3s. I had to buy some V/P parts to make it work but the manifolds and elbows I got from Barr Marine. It all fit together well and works great. Hope your engine issue gets worked out...