Yanmar 4JH3-TE cut out while underway

[Irish Rover]

Was out for a few hours today. I usually motor on just one engine at 2,200rpm. Today I ran both engines hard for around 15 minutes [3/4 minutes at full whack] which I do once every few weeks or 10/15 hours. Both fine afterwards and ran them at tickover while I was anchoring. After a few hours anchored I was returning to base and running the stb only at my usual 2,200. After around 15 minutes it cut out completely - I noticed a momentary drop in revs before it died. I came home on the port engine. I assumed it was fuel so I checked the inline filter - all clear - and the separator - diesel running clean no sign of water -. It started first turn and ran sweet as a nut @ 750 rpm. Revved hard in neutral and all seemed fine. Oil pressure and temp normal. The marina is too dirty to get in to check if there's something wrapped around the prop but I don't think so - after it stopped and I was motoring on the port engine I had a look down at the stb and could see the shaft free wheeling as it always does on the idle engine.
Going to go out tomorrow and see what happens but if anyone has any ideas I'd be very interested to hear them. One thing that occurred to me was that the inline fuel lift pump might be faulty - they're cheap so I ordered a replacement anyway which I'll hopefully have in a few days.

 

[kippers26]

If you have any multipin connection blocks on the wiring loom check them for corrosion or being loose . i had a similar problem earlier this year and found that 2 of the connectors on a 12 pin socket were badly corroded the other 10 were perfect.

 

[Irish Rover]

If you have any multipin connection blocks on the wiring loom check them for corrosion or being loose . i had a similar problem earlier this year and found that 2 of the connectors on a 12 pin socket were badly corroded the other 10 were perfect.

Thanks. So you're suggesting it could be an electrical fault - what exactly would need to fail to make the engine cut out.

 

[kippers26]

The corrosion on my connector was the feed to the solenoid valve on the fuel pump. and it cut of the fuel supply to the engine.

 

[Irish Rover]

The corrosion on my connector was the feed to the solenoid valve on the fuel pump. and it cut of the fuel supply to the engine.

Thanks. Food for thought. I don't think mine has multipin connectors. Looks like all connectors are old fashioned spade type but I'll certainly check it out.

 

[graham]

How full is the tank? If the level of fuel was low possibly you have sucked a bit of air into the system.

 

[Porthandbuoy]

Could be some crud in the tank large enough to block the pick-up line. Lift pump suction holds it in place. Stop the engine, lump of crud falls to bottom of tank and all seems fine . . . until the next time.
Have you got a vacuum gauge on the filter?

 

[Irish Rover]

How full is the tank? If the level of fuel was low possibly you have sucked a bit of air into the system.

Currently around 30%. I generally fill when it gets to 25%.

 

[Irish Rover]

Could be some crud in the tank large enough to block the pick-up line. Lift pump suction holds it in place. Stop the engine, lump of crud falls to bottom of tank and all seems fine . . . until the next time.
Have you got a vacuum gauge on the filter?

Possible I guess. No vacuum gauge.

 

[ean_p]

The corrosion on my connector was the feed to the solenoid valve on the fuel pump. and it cut of the fuel supply to the engine.

Do you not think that the need for a 'permanent' electrical supply is a bit of a weakness....?

 

[Bilgediver]

Thanks. Food for thought. I don't think mine has multipin connectors. Looks like all connectors are old fashioned spade type but I'll certainly check it out.

I would concentrate on the stop solenoid circuit if it is definitely energise to run. If you have no multipins then check the spade connectors around the ignition switch or other locations as well as engine end. Your wiring diagram should tell you which colour wire to trace.

 

[ChromeDome]

All sorts of electric connectors in boats need looking after, not least when old(ish).
The Original WD40 is a popular Water Displacement (and a lot other) product, just don't think it will protect or lube much.

Specialised Contact Cleaner and Protector products are plenty available.

 

[Bilgediver]

All sorts of electric connectors in boats need looking after, not least when old(ish).
The Original WD40 is a popular Water Displacement (and a lot other) product, just don't think it will protect or lube much.

Specialised Contact Cleaner and Protector products are plenty available.

Just do not use the wrong product in the wrong place. I could tell a story here about a ship's radio operator who did just that and it required a surgical operation to sort out a wafer switch in a transmitter tuning circuit due to the product used having conducting properties resulting in a burnt wafer. Amazing what araldite will fix.

 

[Irish Rover]

Had a prior arrangement today with 2 friends currently on holidays here so I took them out for a spin. We motored for around 2 hours on the subject engine @2,200 rpm in calm conditions. Never missed a beat. Meltemi got up quite strong around lunch time and our return trip was rough enough again @ 2,200 on the subject engine only. Any crap in the tanks would have been well stirred up. Still never missed a beat. I'll have more time tomorrow to check connections and to clean and/or spray some contact cleaner on them.
Thanks for all the responses.

 

[Bilgediver]

Had a prior arrangement today with 2 friends currently on holidays here so I took them out for a spin. We motored for around 2 hours on the subject engine @2,200 rpm in calm conditions. Never missed a beat. Meltemi got up quite strong around lunch time and our return trip was rough enough again @ 2,200 on the subject engine only. Any crap in the tanks would have been well stirred up. Still never missed a beat. I'll have more time tomorrow to check connections and to clean and/or spray some contact cleaner on them.
Thanks for all the responses.

That is the problem with diagnosing a poor connection. You never know when it will strike. One other thing I have done with poor connections, had a few on the club boat. I keep a wee tube of copperslip grease handy. It is available from Halfords. I smear it on the male ends of connectors before connecting.. It helps lubricate the connection and reduce corrosion. Do not be extravagant in the wrong places as it is conductive.