Collective Wisdom

[Charlie]

My engine, a Yanmar 4JH4E, is about ten years old. I have been proactive in getting rid of rust and then repainting it. Unfortunately when inspecting the oil pan I found that there was a fair bit of rust on it. I have a couple of choices. 1) Remove the engine from the boat and give it a good going over to clean and inspect the engine. 2) Raise the engine about 15" and replace the oil pan and 3) wait for the rust to eat through the oil pan then, since the engine will be lighter with no oil, remove the engine and buy a new one.

I will have about 25" inches to work on the oil pan. I was thinking of lifting the engine and securing it by adding a coupling, a nut, and some all thread. That way I can get the engine all the way to the top of the engine compartment.

Anyone have other ideas?

[tkeithlu]

Consider: Determine where the rust came from, and stop it. Rust on the outside might means contact with salt water, given that this is a place that easily gets oily. If it's getting sprayed, such as by a leaky water pump">raw water pump, put an end to it.

Then, remove as much rust as you can without moving the engine, given that moving it means not just lifting it, but disconnecting it in bunches of places and then reconnecting and aligning it when you lower it.

Then, prevent further rust either by painting it (preferred), or simply wiping it down with an oil film.

Then, either go onto the next project or go sailing.

[s/v Jedi]

Get a steel brush under it and clean as good as possible, then use the POR15 system incl. cleaner and metalprep. Should fix it.

[Compass790]

I'm with post # 2 &3
Lift it if you must. Check the pitting isnt too deep but there is no real pressure on the sump so painting will be good.
I'm a fan of coal tar epoxy paint if you can get it, lasted 17 years ( sold boat) on a steel keel & the only rust was from collision damage when rocks got in the way. Should outlast the internals.
If you buy a new pan paint it with that anyway.

[Jammer]

Clean up and paint it as best you can in place. Put down absorbent pads if you don't already have them so that you will be aware of any leaks as soon as they occur.


Pan leaks are rarely serious when they start.

[Wotname]

I with all the above ideas.

25" is a reasonable amount of space to work with. Awkward yes but doable.

If most of the rust is removed and coal tar epoxy paint is not available, I would go with POR15 system incl. cleaner and metal prep (thanks to Compass790 and s/v Jedi).

A spray can of zinc rich steel primer is a distant third but still OK, IMO.

[RaymondR]

You'll never get the prep good enough to do a long life epoxy paint job without pulling the engine out. Just clean all the loose rust off it and give it a few coats of Marine Penetrol or boiled linseed oil and recoat it regularly. The most long lasting coating for non traffic places is pitch or one of the crane wire dressing coatings but I don't know how they would go on a hot sump.

[LittleWing77]

Originally Posted by RaymondR

...and give it a few coats of Marine Penetrol or boiled linseed oil and recoat it regularly. The most long lasting coating for non traffic places is pitch or one of the crane wire dressing coatings but I don't know how they would go on a hot sump.

Does anyone know - I thought linseed oil was highly enflammable?

Is that why one boils it - then it's safe for a hot sump?

LittleWing77

[s/v Jedi]

Oh those products were already in use with the Neanderthalers :facepalm pitch? Boiled linseed oil?

So I guess you don’t know what POR15 paint is. POR stands for Paint Over Rust. It is a combination of paint and a rust converter. It can not be beat in this case because you can roll it on without moving the engine at all. Use a mirror or borescope camera to check.

[RaymondR]

Originally Posted by LittleWing77

Does anyone know - I thought linseed oil was highly enflammable?

Is that why one boils it - then it's safe for a hot sump?

LittleWing77

Boiled linseed oil was the basis of most paints before they started using synthetic resins. As a natural product it tended to be expensive and of limited availability. So when you go to the art gallery you are some times looking at paintings made from natural oil, based paints hundred of years ago and still in excellent condition today. Natural resins form exceptionally durable substances. Amber is sometimes found with insects inside. Tree sap traps the insect and the sap eventually hardens to appear stone like. Amber is millions of years old.

When the linseed oil is boiled the volatile components are evaporated off which tends to shorten the time required to dry and form a durable coating. The slow drying allows the oil to penetrate more readily. Marine Penetrol is a mixture of oils which does the same thing as the boiled linseed oil. These natural products tend to remain plastic much longer than the synthetic resins which accounts for their greater durability. Because they dry slower they also tend to penetrate porous surfaces more thoroughly than the synthetic resins.

Mixing cement into the oil as a filler makes it basic which also tends to inhibit corrosion.

Pitch or tar also provides excellent protection as the hydrocarbon based oil in it does not dry out and "wets" the steel forming a water rejecting film which prevents water from wetting the steel surface and promoting oxidation.

Modern synthetic resins based paints do an excellent job if you can provide a very clean, keyed surface such as that achieved with sand blasting however they perform very poorly otherwise.

[Compass790]

Originally Posted by RaymondR

Modern synthetic resins based paints do an excellent job if you can provide a very clean, keyed surface such as that achieved with sand blasting however they perform very poorly otherwise.

No argument with your post except the above bit.
This statement wasnt true in my experience in painting the steel keel I talked about in post #4
Had no budget for sandblasting & it wasnt allowed in slipway anyway.
What I did was wire buffed it, treated with rustkill ( phosphoric acid largely)
Was far from a pristine surface before painting
Then painted with coal tar epoxy primer & multiple top coats of a different epoxy.
Chemically no argument blasting is better.
Current engine was given a power wire brushing & zinc spray with lacquer topcoat on rebuild, its 5 years old approx & mostly fine.
Just experience no theory.

[dfelsent]

1997 2900 hour 4jh4-te owner here. My pan still has paint. Coat the pan by all means. Good idea.
But why the issue? I’m fortunate that the engine has its own bilge sump that stays dry. Mostly.
What’s your root cause for the corrosion?
Recoat for sure. Find the source of the corrosion too. It’s likely more than just age.

[Wotname]

More to the linseed oil story (for trivia fans).

Raw linseed oil is used as a stock food supplement and it's human counterpart is flaxseed oil.

In the good old days, one would paint one's own barn with raw lined oil but would use boiled linseed oil if painting the neighbour's barn!

[Charlie]

It is really difficult to access the bottom of the oil pan. It took me 15 pictures to get this decent one. As suggested I was looking for the source of the rust.

My engine bilge is not completely dry.

At first I thought that the paint job was suspect. Then I remembered when I changed the motor mounts I used a jack to lift the engine. I had used wood blocks to protect the pan. My theory is that there was a point load that cracked the paint and has allowed the rust.

I spent quite a bit of time with a wire brush trying to get the large rust flakes off. It was difficult at best. I am going to try with a small right angle drill and a wire wheel.

As far as removing the engine I have decided to go ahead. After talking with a fellow Sceptre 41 owner who had recently done this it doesn't sound too difficult.


Seeing as I want to redo the sound proofing and paint the engine bilge I am going to completely remove the engine take it home, put it on an engine stand, give it a good cleaning, and touch up the paint.

I will wait until winter to do so.

Thanks for all your contributions and the trivia facts.

[Compass790]

Originally Posted by Charlie

It is really difficult to access the bottom of the oil pan. It took me 15 pictures to get this decent one. As suggested I was looking for the source of the rust.

My engine bilge is not completely dry.

At first I thought that the paint job was suspect. Then I remembered when I changed the motor mounts I used a jack to lift the engine. I had used wood blocks to protect the pan. My theory is that there was a point load that cracked the paint and has allowed the rust.

I spent quite a bit of time with a wire brush trying to get the large rust flakes off. It was difficult at best. I am going to try with a small right angle drill and a wire wheel.

As far as removing the engine I have decided to go ahead. After talking with a fellow Sceptre 41 owner who had recently done this it doesn't sound too difficult.


Seeing as I want to redo the sound proofing and paint the engine bilge I am going to completely remove the engine take it home, put it on an engine stand, give it a good cleaning, and touch up the paint.

I will wait until winter to do so.

Thanks for all your contributions and the trivia facts.Attachment 223813

If you have a 5" angle grinder it will be better than a drill. Get a woven wire brush called a pipeliner if you are going to do it with the engine removed, it'll tear that rust off no worries. Even a cup wire brush will be fine.
Oil pan certain doesnt look like a throwaway from your photo.
Good luck with it