Cruisers & Sailing Forums (
-   Engines and Propulsion Systems (
-   -   Yanmar "safe mode" (

capn_billl 06-01-2020 10:23

Yanmar "safe mode"
I'm sure this isn't the first post of this nature, but my for trip on new boat, I'd like to get as much info as possible

Yanmar 4JH45, one runs great, the other goes into "safe mode" after half hour. turning it off, waiting 15 mins, then restarting runs normally for half hour, then back to safe mode.

I'm assuming overheating.

When running water comes out of exhaust, I haven't seen this engine run enough to know whether it is "normal", or weak.

I checked the impeller, it looks good, but I'm going to replace. I opened the sea cock, water comes in. the sea filter looked clean enough. the hose was stepped on, and oval shape, I may replace, or shorten, it runs a loop completely around engine compartment, (how it got stepped on).

Alternator was burnt looking, (and smelling), that will be replaced.

Fuel looks dark orange, (old, or dyed?).

Anything else I should check?

I'm driving mostly on engines around the Florida coast. Having a good engine is very important to me.

I checked coolant level, it looks good. the engine only has 400 hours, and is 2015. Other than clogged injector, or coolant, I can't think of what would go wrong.


capn_billl 06-01-2020 10:26

Re: Yanmar "safe mode"
I just thought of a couple more.


Clogged heat exchanger?

Dsanduril 06-01-2020 10:46

Re: Yanmar "safe mode"
Unfortunately there are a ton of sensor faults that can send you to safe mode, so reading the DTC (diagnostic trouble code) is usually the only way to get to the bottom of the problem. You can look at the DTCs and safe mode responses in the Yanmar 4JH45 Operation Manual, the Safe Mode chart starts on page 110 (and carries on for 4 pages). Depending on the display/instrument module you may be able to read the DTCs on the display, otherwise it requires getting into the CAN.

Note that there are four RPM levels in Safe Mode; 2400, 1600, 1000, and idle. If you can't get to the DTCs then knowing which RPM the engine is selecting can help narrow the diagnosis.

After the temperature stuff you've chased, fuel filter and flow would be a first guess just because of your notes, but after that fuel pressure and crank angle sensors seem to be the most common culprits (and the problems seem to be the sensors, not what they are measuring). Good luck.

FPNC 06-01-2020 10:53

Re: Yanmar "safe mode"
What temperature is the engine when it falls into safe mode?

What temperature is the engine that keeps running?

capn_billl 06-01-2020 11:16

Re: Yanmar "safe mode"

Originally Posted by FPNC (Post 3050617)
What temperature is the engine when it falls into safe mode?

What temperature is the engine that keeps running?

I don't remember exactly, but I didn't see a big difference.

All times are GMT -7. The time now is 18:21.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.