Cracked Engine block

[Noes]

Hi there
I just recently bought my first boat with a VP 4,3 V6 225 hp from 1998 in it. I found out that there was a bit of water in the oil, so i decided to pull the manifolds off to presure test them.
They are fine.
Then I presure tested the engine block, and it seems like that's the leaking part unfortunately.
Compression tested all 6 plugs, great compression.
So i now think the most likely part to have failed is a cylinderhead.
Assuming i have a cracked cylinderhead does anyone have any experience with block sealer like these, they seems very promising, though i have only heard of them used in cars.
http://www.irontite.com/store/index.php?main_page=product_info&cPath=1&products_id=142
No matter what i am gonna put a heatexchanger on the engine as i think that is the way to go from now on.
Using this would save loads of money and time for me, but can anyone tell me about experience with this stuff?

 

[garbageguy]

I have tried various sealers in the past, on older cars, never in a boat. If a car has running problems, you pull over - in a boat, it can be quite different. I am not an engine expert, just my .02

 

[alldodge]

I would not use any sealer in a block or head. Pull the motor apart and see what is cracked or replace the unit.

Might change the oil and see if the water comes back, may have come in another way

A heat exchanger is great for the motor, but almost never good to add one to an old motor. Need to do this after fresh rebuild or new install

 

[Lou C]

I think at this point you need to find out where the leakage is occurring, it could be a cracked head, block or blown head gasket, of the three, the HG is the cheapest parts price wise. Do you see rust trails on the sude of the block?

 

[Lou C]

Could even be something simple like leaking intake gaskets or a rotted or cracked intake manifold (the water passage below the thermostat that connects to the front of each cyl head...)

 

[Bondo]

Then I presure tested the engine block, and it seems like that's the leaking part unfortunately.

Ayuh,..... Welcome Aboard,...... How did ya do this test, 'n please explain the results, in detail,.....

 

[fishrdan]

If the engine was raw water cooled before, adding a heat exchanger will cause problems, rust bits will clog up the heat exchanger. This isn't an issue with a raw water cooling, since the rust bits get flushed out into the lake, but on a closed cooling system they will plug up the heat exchanger.

Block seal takes heat and pressure to work, so unless you add the heat exchanger (see above) the block sealer won't work. Block sealer won't work with a raw water cooled block. I don't use sealants in the cooling system, unless it's an emergency.

Agree with Bondo, exactly what was done to pressure test the block.

I had a bit of water in the oil on my engine. Bad manifold, leaking water into the manifold, then into a cylinder, past the rings, and into the oil. Acetone tested the manifold to conform it was bad. Replaced manifold, water no longer in oil...

 

[Scott Danforth]

you cant use a sealer in a marine motor with raw water cooling

you cant put a heat exchanger on a used motor unless that motor has had anti-freeze in it its entire life

agree with Bondo, specifically how did you test?

 

[Noes]

Thanks for the replies guys, sorry for the late answer. Sad to hear about the Exchangers being a bad idea, really seems worth the effort to a good engine.
Specifically -
I Blocked off the exhaust water outlets by blocking the hose with fittings. A presure gauge on one, and a ball valve on the other. blocked off the water inlet the same way with a ball valve, like shown in the picture.
Put around 1,5 bar of air presure on it, and within 15 minutes it was down to .7 bar.
I know 1,5 bar is not a lot but didn't want to blow a gasket if nothing was leaking.
Didn't wanna put water in as i have just replaced the oil.

I believe next step is to pull the waterpump of to troubleshoot each side, and find out which head to pull off.
Might do an expection of both just to make sure everything is fine..
Really expensive hobby i have gotten.. Just sailed it once :blue:

 

[kenny nunez]

Pull the intake manifold and the crack will be just below the cylinder head surface, the castings are the thinnest at that point, that is where the Chevys like to crack. The heads need to be tested and may have survived.

 

[Bullett4006]

Just finished going through this with my 99 volvo 4.3. There was a crack in the valley on the cylinder #1 water jacket. I picked up a junk boat with a good 4.3 omc engine for 150$ and swapped all of my components over to it. Just got it running yesterday, now I'm just waiting on my new gimble bearing and shift cable to come in and I'll be ready for summer.