Yanmar YSE8 Engine oil

[lupo1]

Hi,

Just bought a sailboat, a CS27. It has an original Yanmar YSE8 diesel installed.

I'm trying to ascertain what engine and transmission oil it takes.

Perusing the engine manual, I'm not quite able to make heads or tail of it. It states that the engine and transmission oil is one and the same. Calling the marina, some say 5W40 while others recommend 15W40. Not sure where the difference is but I'm sure there are not too many correct answers.

Also, when doing the oil change, does the transmission oil drain at the same time as the engine oil or are there two separate drains. I looked around but could only find one drain and two fill ports.

Any hints/assistance would be appreciated.

[Compass790]

Welcome to the forum Lupo 1
Yes engine & transmission use the same oil. They have 2 seperate compartments or should be but if the crankshaft seal goes they are common. Think there is a drain bolt on the back of the transmission near where shaft comes out. Trans only takes about 1 litre from memory but there should be info in the manual. If not download a Yanmar ysm8 manual which you should do anyway as it has more info.

The original spec was for straight 30 monograde but 15w-40 is fine. We have been using it & 20w-50 for 10 years in our ysm8 which shares most parts.
PM wotname if you want exact location of drainbolt for trans as he has a YSE8.


I'd be more worried about the exhaust mixing elbow elbow than the oil viscosity as when they fail they can destroy the engine. Good to check & change oil though when you get a boat

[Wotname]

YSE8 sump drain is on the LHS (looking from the gearbox towards the front PTO pulley) i.e. on the opposite side of the head.

[Rucksta]

Wow! CF in action

[Wotname]

Originally Posted by lupo1

.........

Any hints/assistance would be appreciated.

As new owner of an old Yanmar YSE8, there an are a few things to know about this engine which has a few differences to later model engines.

1. Oil Filter - give the T handle a couple of turns before the first start of the day. Remove and clean the filter once a year (or so). Refer to the service manual.

2. Exhaust Elbow/mixing point - ensure this is in good condition. Inspect and replace if at all suspect. Compass790 (above) is 100% correct. If this item fails, you WILL get salt water in the cylinder - which obviously is not nice and can be expensive!!!

3. Some folk experience head gasket failures but IMO, this can be largely prevented if you you leave the piston at TDC on the compression when leaving the engine shut down for more than a few days. This ensure both valves are closed and the cylinder (combustion chamber) is almost entirely empty of air. This is kind of important on a horizontal cylinder engine as any condensation occurring in the cylinder collects at the head / gasket / cylinder interface and can cause pitting in the cylinder wall and possible corrosion of the head gasket. It easy enough to do, rotate the engine until you feel the compression resistance, then open the decompression lever to allow you rotate the crankshaft about another 60 degrees. Reset the decompression lever back to normal. Have beer . Note the front PTO pulley is not directly connected to the crankshaft. I don't remember the gear ratio between the PTO and the crank but I'll look for it later and if I find it, I'll post it here.

4. The Injection Pump governor linkage on a YSE needs to be adjusted occasionally (Yanmar say every 500 hrs IIRC). The procedure can be done by the owner if you are careful and follow the directions exactly. The first time might prove challenging to some but after you know the procedure, it is simple and straightforward. Again - see the service manual or the operators manual.

5. About the only weak point of the YSE/YSB/YSM is the oil pump. It wears faster than modern motors and if you operate with marginal oil pressure for too long, you get excessive bearing wear. While the big end bearings are available, the crankshaft main bearing on the flywheel end is harder to source and EXPENSIVE. I paid something like $500 for the genuine Yanmar bearing a few ago. I could not find an aftermarket item. The other crankshaft bearing is (or was) readily available and priced normally. Once you have got the rest of the maintenance of the engine sorted out, I suggest you check the existing oil pressure. Ask here if you need more detail. The oil pump can be refurbished but it takes a bit of work.


The YSE is about 50 years old but it is a tough unit and if looked after, it will dependable for many years yet. All it really wants is clean oil, clean fuel and a good exhaust elbow.

Get yourself the YSE operators manual, the YSE service manual and the YSM service manual. The YSM service manual has much more detail than the YSE manual. All three gives you everything you need to know. If you can't find them online, PM me and I will email you pdf copies.

Is your engine fitted with the hand start option?

[GordMay]

Greetings, and welcome aboard the CF, lupo1.

Yanmar “YSM” Series Service Manual
➥ http://www.devill.net/Documentation/Yanmar/YSM-8-12.pdf
or
➥ https://www.slideshare.net/kjsekmdfh...-repair-manual

Yanmar “YSE” Series Service Manual
➥ https://www.sailingthanksdad.com/doc...viceManual.pdf

Wotname reliably gives good advice.

[lupo1]

thank you for the info. I'll take a look at the manuals.

Yes, it does come with a manual start but I was advised to be careful with it. Apparently it has significant kickback.

[Compass790]

Terrific post Wottie. I had faith you would point out the things to be aware of.

[grantmc]

Here's a link to me Google Drive folder Yanmar in which you'll find a copy of a tatty old manual for a YSE8. Feel free to download.

https://drive.google.com/file/d/1Kl8...usp=drive_link

If the link doesn't work then send me a PM and I'll send back the pdf.