New Motor - oil in water??

[jeffconnell12]

Hey guys - here is the background of the latest events.

1974 mercruiser 3.0L - I took it out on its first trip (as the new owner) and the coupler went out within 10 minutes.

After repairing this I started the motor on earmuffs with new oil - after a shortwhile i noticed the oil had water in it and emulsified quickly. I thought this happened due to me leaving the motor uncovered during a rainstorm.

Fast forward a year and i've purchased a newly built long block (from a reputable machine shop). I take it out on the lake and break it in. Unfortunately I missed one small plug that goes where a secondary oil dipstick/drain hole is.. so oil shot out of the oil pan/block (approx 1/2 liter). The oil was clean and no signs of water.

I stopped the motor and put the boat away. The next day I added the necessary oil then ran the motor on some earmuffs and checked the oil after about 1 minute.. water. Small amount but enough that it was definitely there.

I can't figure out why a 3 hour test ride wouldn't result in water getting in the oil but the second i put this new block on earmuffs i get water in the oil (just like the old block).

Assuming the block/head are good could it just be the manifold/riser? I've removed the old one but don't know how to tell if there is an issue. I can see a small amount of surface rust forming on two of the valves however.

I'm in canada and to replace the exhaust is over $1000.. i'd hate to do this and have it not fix the issue.

any suggestions? Thanks!

 

[Scott Danforth]

pressure test the block and heads

how does the gasket surface look on the manifold?

have you acetone tested the manifold and elbow?

how long did you run on the muffs?

 

[jeffconnell12]

Haven’t tested block or manifold yet.

The original gasket for the riser was separated and I RE used it!! Foolish me (it was the only gasket not provided in the kit). I used a fair amount of high temp sealer with it tho..


here are some photos if they help with diag .. learning as I go.

 

[Rick Stephens]

You can remove and fill the water jacket of the manifold with acetone if you think that might be the problem. Acetone will quickly leak through a crack that water won't go through except when the cast iron is hot. With the water jacket full of acetone you can see if anything is seeping through into the intake or exhaust.

Aren't that many places for water to get into a 4 banger. Is the exhaust shutter in good shape? Another way I have heard of is if when loading the boat on a trailer the stern of the boat gets deeper in the water than the riser on the exhaust as the boat is raised on the bow.

Use only Mercruiser OEM exhaust gaskets. They are the only ones that hold up.

I don't see anything sketchy in your pics. A little rust, might have introduced a little water there somewhere through the exhaust. Hard to tell. Check your shutter and test the manifold, proceed from there.

 

[nola mike]

Idk Rick Stephens , that rust you don't think could be the entry point?

 

[Lou C]

Agreed I have old pix of my 4.3 when I was changing the manifolds and there was no rust at all in the exhaust ports even with 100% salt water use.

 

[jeffconnell12]

Well the exhaust flapper is completely gone! Nothing but the hinge/pin they'd attach to.

I guess a good start would be replace that and test the manifold and definitely replace the gaskets assuming the manifold checks out.

The mating surface directly between the two slightly rusty ports seems quite thin - i checked my old head and it offers a much wider surface for the gasket. Would this not matter considering if it did leak between them it would just be exhaust coming out?

The old head had more rust than this one and would have had the same exhaust/riser on it before i swapped the long block. It also had water in the oil (much worse).

thanks for the continued help guys

 

[Rick Stephens]

Note that the flapper went somewhere... might still be sitting at the bottom of the pipe.

 

[nelliejohn]

I have a 3liter mercruiser replaced the exhust manifold and riser but am I getting water on top of cylinders one and two anybideas on why

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