Yanmar 4BY help needed

[captstu]

My engine is reaching out for some love.

There seems to be two problems that Might be related?

1. The engine will not start. When I turn the key there was no warning horn and no red light on the keypad. I figured, dead Engine battery. No problem it's three years old and I'm ready to replace it anyway. I turned the bridge switch to the emergency start position and the engine started immediately. How the puzzle: I set the Garmin to read engine voltage and turn off the emergency start switch. The voltage read somewhat under 12 V. When I brought the engine up to speed for about 30 seconds the voltage climbed the 13.8 V. This is as expected since the alternator cut in and the chargeing relays cut in affectively hocked and the three banks of batteries together. After 30 minutes or so of running at speed, The engine coughed twice and cut out, the red light on the key did not come on, and There was no indication of why it stopped. I waited a second, cranked the engine and it started to run normaly. The problem reoccurred twice during the day.

2. The second problem may be related to the first but I don't see how: I was running along normally, The Yanmar gauge alarm indicated engine and over temperature. The engine shut down automatically, a few seconds later the raw water overheat alarm sounded. OK I figured the impeller shot. Just to be sure I removd the cover from the raw water sea chest and found no obstruction. I opened the valve and allowed water to overflow the Seachest to make sure the thruhull was not clogged. I closed the line valve and started the edge briefly and it sucked the water out of the Seachest. By this time the engine cooling water was sufficiently low to permit restarting the engine. I started the engine and observed water coming from the exhaust and significant water flowing through the Seachest. By the time I returnd to the console the engine coolant temperature had dropped to Well within to the normal range. Before I change the raw water impeller, i'm hoping to better understand the problem.

I'm hoping for suggestions or both of the problems. My guess for number one is I have a loose wire between the battery and wherever the engine picks up at electric power for other than the starter. I'm guessing this wire has a loose connection and is failing to deliver adequate power to the edging even when the battery is being charged over 13 V. Any idea where this wire is connected?

I believe problem number two is a red herring. I must've just picked up some crap at the inlet that caused a temporary raw water overheat thus triggering a coolant over temperature alarm.

Ideas please. Thank you!

 

[Brian B]

Start with the battery, replace if necessary. These engines are known to be very susceptible to poor ground issues. Make sure all connections are clean and tight between battery and engine. Engine ground wire should be on port side of engine top of the transmission, remove and clean well. Remove and clean ECU fuse, should be in battery compartment. Also check the ECU connection to the ECU itself, top connection on the black box, port side of engine. Check wire going to alternator and aft of the alternator on my boat there are two positives secured to the hull. After cleaning connections I spray them with Corrision X. I also just added a battery load tester to the boat so I can get a true condition of the batteries.

 

[knotflying]

I think your assumption on number two may be correct.

Number one may be more difficult. It was not clear to me the sequence of things. If you turned on the parallel switch to get started and it started, Lets assume for now that your engine battery was dead and that got you started. However, the relays may have kicked in because they were now reading high enough voltage on the engine battery because of the parallel switch. With a short run, if you then turned off the parallel switch the engine battery only had a surface charge, lost it and then the engine died.

The boat is wired differently then a car where after a boost the alternator will keep you going. So my first inclination is bad engine battery. Before you start looking for a loose connection I would check the battery by making sure it is fully charged, let it rest and then do a load test. If the battery is okay start looking for a loose connection.

Additionally, the 4by2 is very sensitive to good grounding. You need to make sure the two wires that go to the ecu are well connected on the engine battery. I also ran a redundant ground directly from the engine battery to the engine block. A bad ground will and can result in erroneous error warnings.

 

[captstu]

This morning the engine started easily. Before starting I check the battery voltages and they were 12.4 V or above each.

The temperature problem did not recover so I am chalking it off to something in the inlet.

The engine sputtered briefly three times in four hours of running this morning. It did not stall and quickly recovered to 3200 RPM.

I am leaning toward a ground or fuse problem, thank you.

I change several other fuses to waterproof circuit breaker's over the years but I cannot find the ECM fuse. I will trace down the wires and look for it when the engine is cool.

I'm also thinking there may be some water in the fuel?? Three weeks ago I took on a few cups of water and was able to drain it from the Racor over the next couple weeks. I did not check the Yanmar filter for water but will do so today replacing it while I have it apart.

These problems seem minor and I probably because I went away on another boat on vacation. Both appear to have as much jealousy as wives and girlfriends.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[knotflying]

The ECU wires should go directly to the engine battery. They may be about 10GA.

 

[captstu]

I see the wire. I'll hunt for the fuse and clean the connections. Tnx


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[knotflying]

I don't think there is an external fuse. It is probably in the ECU itself. Make sure the connections at the battery are good and clean.

 

[captstu]

Significant progress today - thanks for all the help, I never would have thought to check the ground without you.

First, I the engine would not start. I traced the wire back from the ECM and found a FUSE in the Generator compartment Unlabeled until tomorrow. It was OK, continued tracing the wire back to the start battery. The Starter, Windless, Charger, Meter, and ECM wires are all stacked on the poor positive terminal of the start battery.

As suggested above, I removed all the wires, cleaned them carefully, and restacked them in size/load order. Tightened the terminal post and all was GOLDEN. But, the wire to the ECM was attached with a 1/2" ring terminal, not a 5/16" as it should be, Thus only a tiny portion of the ECM wire was touching anything with power. No amount of cleaning will fix the obvious problem, so I ordered a bunch of marine grade terminals that were 10 gauge to 5/16" ring. I will replace all the terminals and install a copper top washer and corrosion protection - should be the end of this problem.

I went for a test ride - a swim and lunch actually. The engine would not restart after lunch and the volt meter built into the Garmin read - volts..

Back to the wires, the red ECM wire is in a wiring jacket with a BLACK (not yellow as it should be) wire. I traced that wire from the jacket and found it was attached to a negative distribution terminal with a nut that was only finger tight.

I removed the 5 wires from the wiring terminal - all different sizes, some ring and some spade - cleaned the and put the back on so I could get home. Engine started fine and I was off for the return trip.

Unfortunately, there was some water in the fuel - so the engine raised a "check engine" indicator and died just under the bridge. Coasted out, dashed back, and drained 1/4 cup water (more or less) from the secondary filter. I've ordered a Racor water seperator to put before the factory Racor so I can catch and drain the water before the water sensor shuts down the engine.

Nice day on the water - under $100 in parts needed. I think I am on the way to correcting the root cause.