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2004 Bf 90 A water in the engine oil

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boathead1012

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Greeting from a four stroke newbie,

Need expert guidance, Bought 18' center console with a 2004 90 with a known engine problem ,water in the engine oil. I have searched the forums and tried to educate myself on this rig. The boat runs and starts fine, has low but even compression across all 4 cylinders (90 -92lbs), plugs look normal, rig seams to have been well cared for until very recently.
Oil was like a milk shake when dropped cold. (no separation). Thermostat was stuck in the open position and flow valve by thermostat was clogged shut. The thermostat housing is in good shape. It has a new starter installed so I pulled that and found the inner housing to appear normal with no signs of water/rust so I think I can rule out he crank seal.
The prior owner was not mechanically inclined. He had been doing a lot of trolling in cold water prior to the problem coming to light. The boat was boatel kept but always used in salt. He told me a shop did the compression check and did 2 oil changes and still got water in the oil.

I am currently waiting for a new thermostat and seals. Could this really be the cause?????

I am thinking the cause is gasket/seal failure due to age. If the thermostat cures it LUCKY ME. If not what is the most likely place to start looking, pull the head (water/oil jacket) breach or the complete power head (gasket/tube grommet). This is were sage expert advice (been there done that )comes in. Any advice greatly appreciated .
Cheers Carl
 
When talking milky oil, and a history of 2 recent oil changes (both resulting in milky oil), I think hope for a thermostat change to fix the issue is pretty remote. A few drops of condensation in the oil filler cap or the upper end of the dipstick, maybe. Milky oil? I don't think so. That's a LOT of water.

If it were me, I'd be looking at what is required to pull the head for a good look see.

I do a LOT of work on the 40's and 50's and I see 1 of 2 things on "milky oil" projects, especially those with a lot of time in the salt. Either the engine was overheated to the point the head gasket was destroyed (does the valve cover show any sign of melting on the spark plug side, where it meets the head? If so, that's a dead give away), -or- the block or head surfaces on either side of the head gasket have corroded to the point the head gasket is no longer able to seal. In either case, the head needs to be pulled for a close inspection. If there is corrosion on the head side, a skilled machinist can often resurface the head to make it reusable.

Manual in hand, this is not a terrible project for a mechanically inclined DIY'er. Only special tool required will be a torque wrench.
 
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Thanks for the input Alan. There are no outward signs of overheating or corrosion. Plugs look normal and are uniform in color, prior owner was a straight shooter (senior navy guy), if it had overheated he would have said. I don't have a lot of faith in the shop that did the work as they didn't even look at the thermostat anywhere in their process.
cheers carl
 
Hi,
Not sure what would be causing the water intrusion into the oil but I think Alan's assessment about the Tstat not being the sole cause is likely 100% accurate.

But I'm mainly chiming in to agree with your thoughts about the competency of the shop. Yes, they should have caught the stat issue but I'm not even convinced those compression numbers are real either. Especially for the engine running as well as you say it does.
I wouldn't rely on anything they reported.

I would probably be thinking about doing a cylinder leak down test on this one with all of the plugs removed to listen for any leakage between companion cylinders. That might reveal something useful about the head to block seal.

Good luck.
 
Thanks for the info and advice. Totally agree on the compression test numbers ,they don't make sense. I know this thing is basically a civic motor so even done cold I would expect upwards of 170 range. I have never actually done a leak down test but know its done TDC tests for weak rings/bad valves. What type of results would indicate a head block seal failure?
One thing I did do was to drain the oil and flush with the muffs on for an hour to see if any water would appear at the oil drain plug. No sign, just wondering if there's anyway to pressure test the whole coolant system .
Don't you just love a good mystery!
I should be in a position to drop in the drink this weekend for the first time and then see for myself what's what.
I will report back with the results.
Carl
 
I've rigged a test hose that clamped right on to the water pipe that normally is inserted into the pump. Of course that require dropping the lower, but in the grand scheme of things, that's not too big a deal.

Regarding the compression numbers, I don't find them (90's) that unusual. They'll start and run good at 90psi. It's not until they drop into the 80's where you start having starting issues, but once started it may STILL run OK! These motors have pistons with rings that are stuck with carbon build up, the victim of never heating up to run at the temps they were designed to run at and/or the victims of inexpensive (non synthetic) oil and/or infrequent oil changes. Actually, I see this ALL the time on the 40's and 50's I see most often that are generally run on pontoon boats. They are only rarely run over an idle....

Last thought, when running the compression checks, you did have the throttle wide open, right? If not, readings in the 65-90psi range are almost predictable. Further, before you get too carried away, it would be nice to verify your readings using a 2nd compression tester - especially if the one you used isn't in use frequently. -Al
 
While I like what you tried to find a leak, it might be that the engine needs to warm up for something to happen. Your run this weekend will probably tell you more.

There probably is a way to pressure test the cooling system but it would involve tear down and block off plate adapters and other things that I'm probably not aware of. So what Alan is suggesting is likely as close as most of us will get.

When doing a leak down test you listen for escaping air....from exhaust....intake... and crankcase to get an idea of where the leakage is taking place.

I also solidly lock the engine from turning and increase the pressure going to each cylinder. With the plugs removed, you can listen for air from a companion cylinder indicating leakage between those two holes. The two inner cylinders will have two companions. If leakage is detected it simply means that there is definitely a problem with head to block seal and that would need to be investigated by head removal. I didn't mean that the test would necessarily find water jacket sealing problems but is something to try if you're already there because of loss of compression.

And YES, I do love a good mystery!
 
Greeting all,
Just completed a 30 + minute test ride running at mostly 4-5k rpm. Little motor ran sweet as a nut. Checked the oil on return and found no trace of water contamination . So yes do a little dance!!!!!
I am accustomed to dealing with what some regard as weird ****, old Sprinter van, old Range Rovers, Yanmar marine diesels , BMW motorcycles, etc. If you had told me this issue could be sorted with a new thermostat I'd of said NO WAY. Well way. I like this kind of weird.


So here is my theory, the prior owner spent $800 on (wait for it) a compression check and 2 oil changes and was subsequently told the engine was still taking on oil.
I'm thinking the shop didn't do squat and just ripped the guy a new one.

So another magic thermostat story. Thanks to all for the advice and input, greatly appreciated.
Cheers Carl
 
Well....I.... DID.... say NO WAY!....
....But.....
...WAY!

Good news for sure! I hope you get many days of fun now in your new water toy.
Thank you for the update.
 
Fingers crossed hoping for continued good luck! Keep a close eye on it for a while!

BTY - when it comes to dealers, I don't. I'll leave it at that.
 
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