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Honda BF90A has WATER IN OIL !!

L

Lunasea

Member
Sad day…..my faithful 2005 Honda BF90A suddenly has water in the oil. It starts and runs beautifully as always. Wishfully hoping it might just be condensation (had been sitting a good while) …but more water/oil mix came out when drained than that would account for. Replaced oil and ran on muffs. Ran well. Stopped and let sit…then cracked drain. A good amount (over 1/2 cup) of ‘clear’ water came out followed by milkshake.

Clearly there is a significant communication between cooling and oil. Will pull plugs and check compression today, but honestly doubt head gasket issue. This motor has always been carefully flushed after each use (yes…salt water here) on my watch of 11 years. It is very clean inside and out …and was when purchased.

Hopefully someone here can point me in the right direction to sort this out. I do have a shop manual, but not sure where to start and what order to proceed that makes sense.

Any and all help is sincerely appreciated! Thanks.
 
Some additional info that might aid diagnosis (well…for someone who knows this motor). Drained oil/water again completely and left drain open. Pressurized the cooling system with hose through flushing port with engine NOT running. Noted water coming out drain. This seems significant to me…..but hopefully someone will provide more insight.
 
Hi,
I have never worked on one of these but kudos to you for shutting her down and trying to figure this out before more damage is done. I really like your "technique" of applying water pressure to the block and that might come in handy as you move forward.

You said that you want a starting point. I don't know but, on other models, behind the water jacket could tell a story. Link just below:


Water, especially salt water, can be corrosive (as I think most of us know) but it is also erosive when flowing .swiftly through obstructions

Behind that cover is where a lot of the "action" is in water flow. Lots of twists and turns where resistance to flow can occur and metal could be damaged or removed. The engine block itself is one of these areas but much more difficult to examine.

I will also include links for other suspect areas for water to oil ingress although, inspection in those areas requires much more disassembly .

Hopefully other folks here....like ian6766....can respond and just cut to the chase as to what's likely happening and where to look. He has much experience with different Honda models. You might PM him if he doesn't answer your post.

Anyway, as I said, here are links showing other components where water might "push through"...


Note the gaskets for the oil pan and mount case in above link. I've worked on many of the twin cylinder Honda models, most of them older,.and it's NOT my experience that these type gaskets fail. Just pointing out the REMOTE possibility.

Also notice item 4, the water grommet. That's where the water you powered through during your test first enters the engine block. Those grommets do fail but won't allow water into the oil IMO.
However, on older outboards with a damaged or missing grommet, I have seen the aluminum badly eroded. Just not all the way through the casting.

See the exhaust pipe in the dotted box with the bold type E5 underneath? I point it out because;

1. It carries water from the cylinder head and;

2. It passes through the oil pan casting making me wonder if the heat from the exhaust might cause some warping or deformity . While unlikely, that could affect the gaskets. Again, just pointing things out.

Lastly, here's the page E5 (look at small type in bottom right hand corner) and the exhaust pipe referenced in the previous link.

This page doesn't show routing of the pipe or it's relative proximity to the components just adding this for your information.

Those dotted or "ghost" boxes with the arrows and bold type reference numbers is Honda's method for showing components, along with their part number and quantity, are found and explained on another page. Knowledge you may need if you decide to "dig in" to this job.

Good luck.
 
Thanks to you both for your replies! Very helpful.
OK….more details to add…..
The plugs all look normal. No sign of steaming.
My cheap compression tester claims 100 psi in each cylinder. If true (big if)….very low, but matched. Not clear to me what would account for ALL cylinders to be low (well, other than wear and whether that jives with it running so well). Guess I figured only one would show up low and indicate trouble location.
Hopefully ian6766 will jump in….
Apparently I will need to bite the bullet and tear this motor to pieces. I suppose it can’t hurt if it’s already dead 😵
Awfully tempting to just put a NEW one on…….Honda is running an EIGHT year warranty offer now. But $$$$$ for NEW!
Thanks again for the help folks.
 
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