Yanmar injection timing

[gfr10598]

I have a 1989 sailboat with Yanmar 3GM30F, with 1800 hrs. I just did a manual measurement of the injection timing, which seems to be about 3 to 4 degrees late.
Just looking for a sanity check. Is this is surprising, or is timing drift on these engines not too exceptional?

Thanks
Greg

[shakey doug]

How did you go obout a ''Manual'' timing check?. Some ways can produce the error you mention.

[gfr10598]

Service manual method. Removed cylinder one injector fuel connection and rotated crankshaft until fuel just started to appear. Repeated 5 times. It is consistently about 4 or 5 degrees past the mark on the flywheel. Discounted one degree for visual detection.
Thanks.

Sent from my XT1053 using Cruisers Sailing Forum mobile app

[hpeer]

My 4jh has a thermal wax advance. When the engine heats up the wax melts and advances the timing a good bit. If you have something similar that could account for the difference.

[ontherocks83]

Originally Posted by gfr10598

I have a 1989 sailboat with Yanmar 3GM30F, with 1800 hrs. I just did a manual measurement of the injection timing, which seems to be about 3 to 4 degrees late.
Just looking for a sanity check. Is this is surprising, or is timing drift on these engines not too exceptional?

Thanks
Greg

Why did you check it in the first place? Was the engine running rough or were you just bored and following the service manual step by step to complete all the maintenance checks?

[a64pilot]

Originally Posted by gfr10598

Service manual method. Removed cylinder one injector fuel connection and rotated crankshaft until fuel just started to appear. Repeated 5 times. It is consistently about 4 or 5 degrees past the mark on the flywheel. Discounted one degree for visual detection.
Thanks.

Sent from my XT1053 using Cruisers Sailing Forum mobile app

I have not read the service manual so this is all supposition, but injectors have a cracking pressure, that is x fuel pressure has to exist first, building this pressure may account for the couple of extra degrees.

[gfr10598]

Originally Posted by ontherocks83

Why did you check it in the first place? Was the engine running rough or were you just bored and following the service manual step by step to complete all the maintenance checks?

I've owned the boat for just a year, and gradually going through checking things. The engine runs a little hot when over 2800 rpm, and retarded timing can be a contributing factor, as can dirty injectors. I've already gone through the cooling system.

The mechanical injection system has no adjustments aside from shims, so I'm just curious if wear alone is sufficient to cause retarded injection, or if my measurement is suspect.

[a64pilot]

Usually heat comes from advanced timing, retarded shows up as low power?


Sent from my iPhone using Tapatalk

[gfr10598]

Retarded both reduces power and increases waste heat. If extreme can also leave unburned fuel I believe.

Sent from my XT1053 using Cruisers Sailing Forum mobile app

[sailorchic34]

It does sort of sound like late timing. How many shims are under the injector pump. On mine, I've only one shim. I generally just listen to the injector popping while slowly turning the crank and note the location on the flywheel. If I remember right its one degree per shim, so you would need to remove 3 shims.

Overheating is generally cooling related. If you have the U bend discharge elbow, the area just inside the elbow where the water is injected tends to build up mineral buildup. Actually there can be mineral buildup in the 90 degree elbow on it. I use a small screwdriver and or bicycle spoke to break up the mineral deposits in both.

If there is mineral deposits, odds are there is mineral buildup at the exhaust hose side too.