Tips for fixing Rust, Corrosion and Water Damage on Yanmar YS8 Engine

Hi Seabreeze community,

I have an old Yanmar YSE8 in my sailboat. I bought the boat about a year ago and I did some work on the engine initially as the engine was not running. The boat was sitting for a few years and the engine needed some work. I am new to this still and just learning about diesel engines and fixing the engine last year was my first go ever at diesel engines (changed hoses, belts, crank chain, starter motor and brushes).

The last four months I didn't have much time and didn't look at the engine much and when I opened it up last week I found a lot of water damage, crystallization, rust and corrosion. No water in the bilge though, so it must just be drops from the water system.

The engine runs just fine and turns on first try but there is some diesel leaking (right side of the engine looking from the front) and water dripping left. My main issue is the water damage.

Any advice on how to tackle the rust, corrosion, treatment and maintainance, eg paint afterwards, as well as changing the water system would be appreciated. I had a look Online for spare parts but YSE8 parts are hard to find and I am not sure about the aftermarket parts I have seen Online.

Thank you in advance.
Yamaha24ft

Yamy, that's a very nice example of an older style engine. I wouldn't be concerned about the rust and corrosion, but if you must I suggest a spray with phosphoric acid or oxalic acid solution, then when dry perhaps some light oil, kero,diesel,lanox etc

Paint won't last unless you go the whole hog and remove the engine for a complete clean. Find out where the water is coming from and fix it. Brush off the worst bits then spray Lanox everywhere. It won't make it look beautiful, but it will slow the corrosion right down. There are quite a few Facebook groups dedicated to various Yanmar models, try looking into that to help build your knowledge.

Cheers, Graeme

Wongaga's right.
This is a case of if you are going to do it , do it right.
I would say a YSE needs to be removed and repainted every 10 years or so.
Did mine 6 years ago , cared for it and have so say it is looking a little tired now.
They are not originally marine engines, but they are getting on for 40 to 45 years old and still run well.
If you want to spread little bits of rust all over the place, where they can do their evil deeds a wire brush in the engine bay is the way to go.

Two hours to remove it.
Take everything heavy off first.
Plug all the holes and pressure wash.
Get into it with a wire brush on a drill and other anti-rust treatment.
Primer and paint.

It might sound like a lot of work , but as a winter project it is not so bad and you will love the shinny new paint job.
Engine will even run better, or maybe not.
The heavy rust that you see on the head is a leak from the thermostat or the zinc. anode (You are keeping and eye on the zinc, aren't you?)
At this stage to stop further rusting I would just go through the process that Wongaga has suggested.
That might be smelly on startup, but hey its an old Yanmar.
You don't need to buy gaskets ( for thermostat and anode), because you can easily and cheaply make them yourself,
Youtube will show you how.
Now you have something to look forward to in the downtime next summer. Lucky!

Lastly, try not to leave it for too long without running it. That can be the death of a marine engine.


gary

Oxalic acid or vinegar will not be aggressive enough. I use "Metal Gleam" for this particular job. It's mostly phosphoric acid and is similar to any of the rust removing products on the market sold for silly money. I use this product on internal flushing on raw water cooled engines and heat exchanged engines as well as all the stainless steel deck gear and fibreglass surfaces on the boat. If your looking at tidying up this unit in situ I would wire brush it the best you can. Mix the acid mixture at 5 parts water to one of acid and slop it all over the engine with a sponge. The acid wont hurt your hands but you can wear gloves. Watch out for your eyes. Keep it wet for 5 minutes or so, longer if you can and agitating with a scouring cloth helps. Just let the acid fall in the bilge it will clean that too. I then pour a warm mixture of truck wash and water over the engine and pump the lot over the side. Let it dry and if you don't paint, run the engine to get nice and warm and spray the lot with lanolin. Now and again after running the engine just top up the lanolin while the metal is still warm.

Oh!

Thank you @garymalmgren that actually really helps. Gives me a good idea about what work to put in and the 'to be expected' aging of the engine. Really appreciate you uploading the pictures. This is such a good forum :)

I do Ramona.
That is why it is in such pristine condition.

This was mine after rebuilt. It was a hell ti put it back. I used a car jack and somehow made it. I am strongly suggesting to disconnect your sea intake and connect it to a 2 lit of vinegar and as soon as all vinegar is gone to shut the engine. It will soften all deposits inside but will not destroy your engine. Do it ones every month and you should be fine. If you can disconnect the engine, clean it off the rust paint, remove the mixing elbow and remove all carbon off. Change the oil, clean the diesel filter out all new clamps and you are good for next 5 years. Enjoy..

@garymalmgren thank you. Will do. I'm slowly learning :)