Milky engine oil, 4 stroke

Tommy c · 20 October 2023, 15:33

I've been gifted a 2003 honda bf5a.
There's obviously water getting into the engine oil as it's grey/milky.
Is this the head gasket or is there another failed gasket that could cause this?
How difficult of a job is it to replace?
It starts easily and runs on idle too
Tia

beamishken · 20 October 2023, 15:56

Quote:

Originally Posted by Tommy c

I've been gifted a 2003 honda bf5a.
There's obviously water getting into the engine oil as it's grey/milky.
Is this the head gasket or is there another failed gasket that could cause this?
How difficult of a job is it to replace?
It starts easily and runs on idle too
Tia

How grey & milky is it? They can suffer from condensation in the oil if they are only ran for short periods & not getting up to full temperature. It takes very little moisture to turn the oil to grey. Obviously depends how contaminated the oil is maybe post a picture of the drained oil

Fenlander · 20 October 2023, 16:21

As Ken says it could just be how it’s been run previously. One option is to change the oil and run it up to hot then drain that oil off as a flush then refill with clean and put into use to see if still gets contaminated.

Tommy c · 20 October 2023, 16:54

Apparently run every year for last 10 but laid up last year. Only used as a sailing boat auxiliary

beamishken · 20 October 2023, 18:47

That does look quite bad, maybe worth trying an oilchange & see how it goes but iirc they suffer corrosion which allows water into the oil can't remember where just now but dont think its headgasket.

User name · 20 October 2023, 18:50

That looks like a fairly significant amount of water to emulsify like that.

Has it been stored incorrectly maybe? Might it have run water back up through the exhaust?
It normally feeds water through the engine and back through the exhaust, so a restriction at the exhaust could also cause it to back fill.

I'd start with a pressure test to see if there are any indications of gasket/cylinder failure at the top end. The fact that it starts and runs well would suggest that it's unlikely to have failed at the head, but you won't know for sure without testing.

Tommy c · 20 October 2023, 19:25

Quote:

Originally Posted by User name

That looks like a fairly significant amount of water to emulsify like that.

Has it been stored incorrectly maybe? Might it have run water back up through the exhaust?
It normally feeds water through the engine and back through the exhaust, so a restriction at the exhaust could also cause it to back fill.

I'd start with a pressure test to see if there are any indications of gasket/cylinder failure at the top end. The fact that it starts and runs well would suggest that it's unlikely to have failed at the head, but you won't know for sure without testing.

Pressure test or compression test?

User name · 20 October 2023, 19:36

Yes, compression test.

Tommy c · 20 October 2023, 21:15

Well I poured the drained oil into an old jug.
Well under the 600ml mark. The handbook gives the maximum as 580?
So besides the head gasket, where would the next culprit be?

beamishken · 20 October 2023, 23:12

Quote:

Originally Posted by Tommy c

Well I poured the drained oil into an old jug.

Well under the 600ml mark. The handbook gives the maximum as 580?

So besides the head gasket, where would the next culprit be?

My money would be on the base gasket below the powerhead but more than likely corrosion is the cause, you might find the casting is u/s once you strip it. My pal patched one up with liquid metal to get a bit more life out of it. Depending what your going to do with it changing the oil & seeing how long it takes to get contaminated might not be a bad idea, could well be bad news when you dig into it.

Peter_C · 21 October 2023, 04:14

A cylinder leak down test might tell if there is a head gasket issue or not. After putting regulated air pressure to the cylinder on TDC, you need to isolate the cooling system and balloon or bag it, taping, plugging, or pinching off fittings like the tell tale. If the bag fills there is a combustion leak. The lower leg will need to be dropped.

There is way too much water in that motor to be considered normal. Possible it was accidentally dropped in the water?

smallribber · 21 October 2023, 06:05

Get all of the old oil out. Put in some fresh oil and run it up in a tub of water as usual. Run it for a short period then see if any water is in the oil. Basically try and see how long it takes for the oil to get water in. If it takes a short time you know you have an issue. If it takes a lot of run time then you might find it is usable as is.

What is your intended use of the engine ?

jeffstevens763@g · 21 October 2023, 19:13

Being a auxiliary it might have been for a swim at some point as others say new oil flush new oil etc before stripping it down

spartacus · 22 October 2023, 11:27

Swap out the thermostat for genuine Honda one and change the oil and run it for a while.

Condition of thermostat normally reveals quite a lot. I read a couple of posts on YouTube about something similar but 8hp. Camera work is atrocious and he swears like a trooper, but you might get something from it. There’s another video as follow-up.

If you tear down you can be in a world of pain unless you have the patience, tools and determination to rebuild. If it was me, I’d order a new gasket set and make it my winter project.

https://www.youtube.com/watch?v=5resu7TXOdc

Tommy c · 22 October 2023, 13:06

This morning I filled with fresh oil.
It started straight up and I left it running for 30mins.
It ran really lumpy.
After 30 mins I stopped it and checked.
The oil level was upto the bottom of the filler cap thread, very watery and grey.

beamishken · 22 October 2023, 14:46

Quote:

Originally Posted by Tommy c

This morning I filled with fresh oil.

It started straight up and I left it running for 30mins.

It ran really lumpy.

After 30 mins I stopped it and checked.

The oil level was upto the bottom of the filler cap thread, very watery and grey.

Oh dear thats not good! time to get the spanners out or sell it for spares or repair

Tommy c · 22 October 2023, 18:35

Quote:

Originally Posted by beamishken

Oh dear thats not good! time to get the spanners out or sell it for spares or repair

Complete tear down??

69cmw · 22 October 2023, 18:39

Quote:

Originally Posted by Tommy c

Complete tear down??

It’s 20 years old. Scrap it 🤷

Pikey Dave · 22 October 2023, 18:42

You’ve nothing to lose. Dismantle it, investigate, re-assemble, learn.

Tommy c · 22 October 2023, 19:26

Quote:

Originally Posted by Pikey Dave

You’ve nothing to lose. Dismantle it, investigate, re-assemble, learn.

I'd be 100% comfortable on a single cylinder 2 stroke doing that.
But a 4 stroke I'm not so sure.
Only way to learn I suppose is to have a go seeing as it was gifted.
Is there a particular sequence I should follow?
Worst case is it would then be ready to be sold on in parts