BF225 Leaking Oil

[brettmarl]

225AK3 with about 1,000 hours.

Engine is leaking small amount of oil when running.

I launched for the season and all seemed OK, then took it for a very long run (70nm) - pulled in to get fuel and noticed a sheen on water and small amount of dripping oil coming from the screw-cover on the upper cowling, also some oil on the rubber grommets around the exhaust. I assume this is just the common exit point for something spilling inside the engine bay.

At first I assumed the worst and that it was was a fuel leak and the oil smear was maybe just some extra oil (maybe from a messy filter change) being flushed by fuel on the way out. It also smelled like gas, but in hindsight I was on the fuel dock and was perhaps being overly paranoid. Checked oil level after sitting for a while and was normal. After shutting down the engine, the sheen in the water dissipated and it stopped leaking. Looking under the hood there wasn't any obvious pool of oil or major leak going on, or any sign of gas leak.

Puttered a long way home (70nm back) on one motor. Next day pulled the upper cowls off at the marina and checked all fuel hoses and water sep / lp-filter etc. Nothing seemed amiss, cleaned all the cowls - which had a little oil on but nothing that felt unusual. Ran it the next day - and other than a very slight sheen when first tilting down - it didn't seemed to be leaking anything when powered up and so chalked it up to maybe a stuck float in the VST that purged and fixed itself.

A few days later - took it on a longer run again (20nm) - pulled into fuel dock and it was dripping oil again - see photo and video. This time the sheen on the water was quite significant - but I think it was still only a drop or two that was causing it.

Took her home and next plan it to pull onto trailer and try and find the source of a leak on land where I can poke around deeper and start pulling intake manifold off to get a better view of where it might be leaking from.

I normally keep boat in the water year round - but this year had it sitting on the trailer for five months (Nov->March) and we had some really unusual low freezing temperatures (9F) and I didn't do anything to winterize the motors - so thinking it's possible freeze damage - however other motor not impacted.

I did do 100 hr service before launching (oil, filter, gear oil), but didn't do anything to disturb things like valve covers etc.

My best case scenario seems to be a bad oil filter/seal, but wondering if anyone has any suggestions of where to be looking when I get it on the hard.

Appreciate the ideas!
-Brett

Video of leak

 

[chawk_man]

Yes, the first thing is to check is the seal on the new oil filter. Also, it is not unusual for have oil leak down into the engine compartment when you change that filter. It tends to stay in there for a while and drips out when you raise the engine. Then check your valve covers. Next, check the seals around each spark plug. They will often get hard and leak oil. See # 4 at:

Honda Outboard 225HP OEM Parts Diagram for Cylinder Head Cover | Boats.net

Buy OEM Parts for Honda Outboard 225HP Cylinder Head Cover Diagram

www.boats.net

If not any of those, keep looking.

 

[brettmarl]

My notes say that I did 800 hr service in September 2021 - where I replaced the valve cover gaskets and plug seals with new. While I was at marina doing my fuel-line checks - I did pull and inspect coils incase one of those plug seals were leaking (had that happen one time with a badly seated seal) - and things looked clean in and around the tubes.

 

[chawk_man]

OK. Keep us posted on what you find.

 

[brettmarl]

Working on boat at marina until I can get it out - as would be preferable to fix without pulling and relaunching.

Last time I inspected a week ago - I cleaned everything up and when I opened up upper cowl found traces of oil here and there with most of it in the chase that attaches to the rubber strip.




Cleaned up all the areas and looked closer for suspicious leaks. Oil filter is fine - super clean under it and all around.

I noticed that the Right valve cover gasket has a little oil on it in both bottoms corners. Didn’t look like much of a leak but the left side was bone dry so it’s something. Also checked the coil tubes again and there was a small amount of oil in #3 tube (also RHS). Overall there was maybe a teaspoon or two of oil sitting in little nooks and crannies inside that I assume is where it ended up when tilted up.

One area that looked more suspicious and had more pooling was the fat hose coming off the RHS valve cover - I always thought this was a cooling hose but the parts diagram has it listed as an oil hose? There was a little 5ml pool in that area and all in the hole it inserted to. It seems this would be consistent with maybe where the valve cover and possible plug leak could end up when dripping.



I pulled the hose off to clean it




and in addition to a lot of oil around the hole, the inside of the tube had a white gunk that looked like lithium grease or something.





Didn't look like what I would call milky oil - it was more viscous.

Put things back together and ran motor at idle for 20m and didn't see any signs of fresh oil inside anywhere.

Took it for a 10 minute drive, pulled into a dock to check things out - and no sheen, things looking better... then took for a longer 30m drive and checked again - this time some sheen in water and some new traces of oil inside. None where that hose was - more in other odd spots - like on the support rail close to #3 plug and below it. But no signs of dripping or how it ended up there.

Would it make sense that the longer runtime is causing the leak as the oil is getting hotter and perhaps thinner and able to seep out more? Based on my attempts to spot it with just idle-time I'm concerned that if I do trailer it and run it in a tank on land - it might be hard to get to the heat/usage level to reproduce the problem and will be hard to know I fixed it.

At this point, I'm planning on replacing all valve cover gaskets and plug seals again. I've never gone any deeper than that before - but given it's got 1000 hrs - would it be prudent to replace head gaskets while I'm at it?

 

[chawk_man]

Keep looking. My only other advice is to not touch the head gaskets unless there are definite indications that they are the problem. Pull the plugs to see if any are oily or sooty.

 

[brettmarl]

Well... back to the leaking oil thread. I think the trim/tilt issue is solved now, and it's possible that some of the sheen I was seen was hydraulic at some point, however...

Today I cleaned everything inside the engine bay - and ran motor for 30m idle at dock - and didn't see a drop of oil anywhere. Put all back together and took it on a 14nm run to get fuel. Pulled into fuel dock - and not a drop of sheen in the water - so declared victory. Woo hoo.

Got back to marina (14nm back) - and was sheening oil again. Gggrrr... quick look under the hood and #3 coil seal is most likely culprit - there was oil on the latch rail below it and oil inside the plug tube. It didn't seem enough to produce the sheen I saw - but it's the only thing that is wet.

I'm really confused why it doesn't leak on idle and why nothing leaks until I've been out for a very long time. Does it just take the oil getting to a certain temperature to be thin enough to leak out? Maybe it takes that long to work its way down around the cowl and eventually out the back. When I shut down the engine - the sheen clears out fairly quick - which makes me feel like I should be able to see a drop coming off the #3 coil area when it's running.

The other thing I noticed - is for a bit as I watched it - it felt like the sheen was coming from the pee stream. I'm not 100% on this as I did see oil on the outer of the lower cowl again - below the two-bolt hatch. It may have just been how it was disturbing the water surface, but wondering if any particular leak would cause oil in the pee stream. Only thing I can think of is lower unit oil via the water pump.

It's discouraging - as it's going to be hard to tell I've fixed it - once I replace the seals and tank-test on land.

 

[brettmarl]

Todays plan is to pack a bunch of sorbent rags into various parts of engine where I think drip is coming from. Then run it and see which rags are oily.

 

[brettmarl]

Pretty convinced my engine oil leak is combination of #3 plug seal (majority) and RHS cover gasket. The plug tube dropped 1/4 tsp or so of oil during my test run onto the rags, and there was a smaller few drops collected below the gasket. I hadn't inspected the plugs themselves, so went to remove #3 and realized that the coil tip was stuck on the plug still. After a lot of fussing managed to get it off - and i'm fairly convinced that the plug wasn't torqued fully. I found a lot of oil on the plug threads as it came out. Cleaned and re-torqued to spec (18NM) and mopped up all the oil in the crack between the metal and the seal. Took it for another long run - and this time nothing leaked out on the sorbent rags but the seal was oily again and some smaller amounts of oil in the tube.

<aside>
Had an interesting chat with local boat.us guy who has same boat and same 225's. He said that he blew a coil once and it was a hot mess - melted and fused itself into the tube and very challenging drill out. Said that if not seated properly they can arc. Also mentioned that he now carries a laser thermometer and periodically pulls his cover off and lasers the top of the coils (without removing) to ensure they aren't getting excessively hotter than they should - which is an indication of pending failure.
</aside>

Parts ordered and onto the trailer she goes...

 

[brettmarl]

This is my #3 seal. Can’t tell if it was kicked out like that due to me pulling cover off or that’s the way it was when leaking. Either way I’d says it’s a smoking gun at this point.

 

[wildebeest]

I dont think there is any way that seal pulled out like that from taking the cover off. They are in there tight. I've replaced some and had to completely destroy the old ones to get them out.