Yanmar 3gmf over heating solved

[eusjim]

I have always been careful to shut down the engine whenever I would get and over temp alarm. As some readers will know, this problem has continued for an eternity.

I was exasperated. Performed every test known to Yanmar and the common man. At one point even suspected a leaky head gasket. Also had been through mixing elbow, seawater impeller, input clog check, crimped hose check, temp alarm check, heat exchanger cleaned, radiator cap replaced, thermostat replaced, etc, you name it.

The problem was simply a slipping pulley on the seawater pump. The pulley nut was tight, but at high RPMs, pulley was not turning the pump at full speed.

The key on pulley had worn and ground a groove into the pump shaft.

This week I had been running the engine at a safe 2200rpm when the overheat alarm went off. Since the problem had never occurred below 2700 rpm, I knew there had to be a new source. Went to check the seawater impeller, and found that the pulley was the culprit. At low rpms it had worked quite normally. At high rpms.. it would slip just a little to reduce cooling efficiency. Who would have thought it!!!

Had to replace the whole pump.. ouch. Just finished cruising for 2 days, often at high speed, and no move over temp alarm.

 

[kloudie1]

Good catch, Jim !! Thanks for posting the find..

 

[Dan Johnson]

Had a similar problem...

three weekends ago. Was leaving Georgetown harbor on the Sassafras in the morning, running about 20 minutes at 2,200 RPM until I crossed the no wake zone markers. Throttled up to 2,800 RPM and within a minute the high temp buzzer went off and warning light lit on the panel. I aimed for an anchorage area and shut the engine down.

When I got out of the channel area, I restarted the engine to get positioned to anchor -- no alarm! Continued to motor at 1,500 RPM -- no alarm. Upped it to 2,000 RPM -- no alarm. Upped it to 2,500 RPM -- no alarm at first, then it sounded again.

Again, shut it down immediately and drifted to the side of the channel. Once forward motion stopped, set out the anchor and began problem solving.

Closed the sea water valve and opened the strainer basket top and pulled out the strainer -- Nothing! This was the easy solution from previous experience.

Went to "worst case scenario" and removed the sea water pump mounting bracket, spun the pump on its hoses and opened the back. Much to my surprise all the impeller arms were still in place and looked fine upon examination. Put it all back to together and reattached the pump to the engine.

Dove into the aft cabin with a screwdriver and loosened the hose clamps on the raw water intake hose and pulled it off. Barely got a trickle upon opening the valve.

I carry a 12 volt tire inflator pump for this very situation. I have a reinforced hose piece that fits over the raw water intake hose barb. In the other end is clamped a standard tire valve. I clamped the open end of the hose onto the raw water intake barb, plugged in the inflator pump, hooked it to the tire valve, and turned it on.

When the pressure read 60 pounds, I opened the raw water ball valve just like you would fire a torpeado, then closed it. I turned off the compressor, removed the hose and opened the valve. "Wallah"! I had a 6 inch geyser!

Reconnected the raw water hose, opened the valve, fired up the engine, and cruised home at 2,800 RPM for the next three hours without a problem. Suspect a plastic bag or some other debris sucked against the hull intake was the root cause.

Tomorrow I move Intrepid to its winter storage marina and winterize all systems.

 

[grooves4u]

Re: Had a similar problem...

Dan,

Your intake air cannon sounds like an excellent idea. I would like to be able to replicate your set-up but I can't quite visualize how to adapt the tire valve to the hose without using gobs of duct tape. Is it possible for you to post a picture of your air compressor hose attachment?

 

[seadaddler]

RV Store

I have a plastic fitting one side male hose threads and other side air hose fitting from RV store that lets me blow out my water lines in the motor home to winterize,so you can do the same with this adapter fitting the raw water hose.
Nick

 

[Dan Johnson]

Grooves...

the compressor and adaptor are still on the boat. Next time I'm down to check on it I'll take a pic of the hose and valve.

What I did was to use a very sharp knife and cut off the flange portion of a standard tire valve assembly so that it would fit inside of the hose diameter that matched the hose barb on the intake ball valve head. The hose itself is a short piece of the reinforced hose that you can get at any home center store. I have two different hoses, one for the engine intake, and the other for the a/c intake hose barb (they're different sizes). I haven't had to use the a/c one yet.

I forgot to mention that the tire valve assembly is clamped into the hose as tight as I can get a hose clamp to screw down on it.

 

[VINN]

had a similar event years ago dan in a blinding lightning storm just outside huntington harbor with my dad, when i first bought the boat. we where coming in just after a priceless sunset sail, and with a mile to go outside, the overtemp alarm came on. it was imperitive to get inside the harbor so we wouldnt be the highest object out there with a approaching lightning storm. i quickly jumped over the side with a waterproof flashlite in pitch black conditions, and found a foot long bouquet of seaweed jammed in the seacock input. i removed it with a screwdriver. when i came back up, hail and rain were coming down in buckets, with lightning shafts hitting the water a 100 yards away. we started the boat and revved up to 3600 and tried to race in to the mooring fields for safety. we were the only sailboat out there, basically a lightning rod. and then suddenly the overtemp alarm came on again. we decided to idledown immediately for the last 1/2 mile overtemping until we could grab an empty mooring, and hunker down during the storm. with another 70' mast next to ours we felt safe in the cabin to rip apart the water pump to see if it was clogged. it wasnt??? 10 pm came upon us soon, and me and my dad were soaked, and freezing in july like a a bunch of rats waiting for the storm to abate. we had to wonder if the launch guy was still there for a pickup. we had a 1/4 mile to go to our mooring, and was still over heating. well we made it out of there without any injuries with allot of uncertainty of what the problem could be. the next day i went to ace and bought a flexible 3/16 poly tube about a foot long and rammed it in from the top of the seacock, and remmoved what was leftover. i thought it would be wise to replace the whole assembly with a strainer on the next pullout, and we never had any problems since. its the 90 degree bend inside thats the problem. this quick fix is good for mussles that grow inside the inlet for long periods in the water. they must start out like little baby mussles the size of a bb, and grow inside the strainer. go figure! but this jig works in a pinch from above, and you dont have to worry about meeting some unwanted strangers under the boat in the dark, if you know what i mean.

 

[Dan Johnson]

VINN...

the hose barb on my intake valve is a straight-thru one, with no 90 degree bend so I don't have a jamming problem. Usually anything drawn into the intake ends up in the strainer cage, which is the first thing I check. If there's nothing there as noted previously, I know I've got a more serious problem.