Water in the oil
 

Ran my new to me boat for the first time and noticed that the oil pressure dropped from 75 down to about 35 after running for approx 10 minutes. Also, thought the batteries were weak b/c it had a hard time starting. Got back and noticed water in the oil. Changed the oil and ran again for few mitutes and same thing happened. I had it checked today and found a cracked header but we are also worried about other damage to the motor b/c of the oil pressure dropping. What do you think?

The motor is an older but "fresh" Merc 800 SC.

thanks!

I would change the oil a couple more times.I suggest using a can of motor flush the first oil change and just regular oil the second oil change.I would doubt that you hurt anything running for that short amount of time.

what about the oil pressure dropping?

What rpm's were you running when the oil pressure went to 35psi

I hope you're in fresh water rather than salt.

yes, fresh water and we were running between 3-4k rpms. I thought that I was still "breaking in" the motor so we weren't running hard.

I don't think you can get water in the oil with a cracked header, you can get it in the cylinder but not in the oil..most likely you have a seeping head gasket or intake gasket....you need to get that water out of there and in a hurry! Do not leave it set any longer than absolutely ness....I suggest to flush out with 1 gallon of diesel and 3 quarts of oil a few times..& you still will not get it all out..change oil filter repeatedly...This is critical..flush that motor !..you are most worried about the rod and main bearings...and you need to locate that leak fast!...I learned the hard way....good luck

Ok, let me back up a bit here...there is a chance your header leak is your problem..you could have a small leak & the water can be getting back through the exhaust port and through the valves down to your cylinders..after you shut the boat off the water in the manifolds could go into the cylinders and leak past the rings to your crankcase.....but if you have a bad leak it would normally lead to water in the cylinder and hydroloc...that is very bad because you will usually do some major damage at that point...again, get this fixed fast because otherwise you are looking at a teardown.

First of all, thank the Good Lord you're in fresh water! If it was the warm salt water we run in down here...

That "hard starting" could be partial hydraulic-ing. Pull the spark plugs and check the tips for evidence of water in the cylinders.

Crank the engine with the spark plugs out and see if water comes out the spark plug holes. It's not unusual for a leaky header to allow water back into the exhaust ports and eventually past the rings and into the crankcase.

I've even seen cooling system water get sucked into the intake manifold from not sealing the intake manifolds bolts properly.

A compression test will help find a bad head gasket.

Good Luck with it.

I am thinking the same thing it would have to get pushed by the rings if coming in by the headers.

I had it twice, first time was faulty head, 2nd time due to leaky exhaust.

What I did (and recommend) is to drain the oil, then fill the engine crankcase full as possible with diesel. Use a oil priming rod (remove distributor) and drill to circulate the diesel for few minutes. Drain, repeat this process, and it will get practically all the water out. Cheaper, easier, faster, safer than multiple oil change technique.

Thank you for all the feedback and help! We did check the spark plugs and they were a little wet. I am having the motor pulled now to check for additional damage. Looks like Jacksonville Poker run is out. :(

Most likely the hard staring was because of the water in the cylinders...but maybe not...you are making the right call by pulling the engine..one thing to consider though, when you changed the oil and still had water in it after running it...Even if you did not have a leak, once water gets in it will take a few changes to not see the signs anymore...in other words, after your oil change, new oil will get contaminated by all the slime buildup and it will look like water is still getting in untill it is cleaned up..it is very hard to tell sometimes..best way to do it is to clean it out by hand, valecovers and heads & drainpan are usually the worst areas..bottom of intake and top pan as well...good luck, I hope you get good news!

try to do a compresion test before the take it out, my save ya some headace or head ya the right direction. It suxs when its a new ride with probs:(

Best of luck and let of know what find.

Rob:D

Strip, you are right. My engine guy didn't do a compression test, b/c he was sure that we had a bent rod with the drop in oil pressure. We pulled the motor and tore it down. NO DAMAGE. :) We did find that both headers are leaking. This is something that I specifically asked the engine builder about before I bought the boat.

Did the boat sit with water in the headers before you water tested it? seems like a lot of water to notice in your oil (that would have to seep past your rings) when not running.I would think while running most water would get blown out. I have had problems with bad exhaust manifolds leaking water into cylinders and finding its way to the crankcase but it took awile to get there. I would do a compression check for sure before running it. If that checks out ok you should pc the oil coolers, check intake and gaskets, another possabality is somebody used the wrong head gaskets, good thing you were in fresh water if you didnt run much after the op drop youll probally be alright. good luck! hope this helps