Help! Engine problem :(

[flightlead404]

Yanmar 3Jh4E. Recently cleaned impller bits from heat exchanger and descaled. New impeller. Raw water and fresh water pump both replaced 18 months ago. Loads of water exiting exhaust, engine running beautifully.

22 hours running at 2,600 from Hilton Head suddenly very slight change in engine tone odd rubber smell. As I’m scratching my head overheat alarm goes off. I’m in a busy seaway and have no option but to throttle way back but keep running for a few minutes (no wind). Next, smoke billowing from under companionway stairs. Shut off engine and use remaining steerage way to get to edge of channel and drop the hook.

Impeller was fine. Replaced anyway. Coolant reservoir cap blown off, coolant everywhere.

let the engine cool, restart, no water exiting exhaust.

Any pointers on the engine issue would be appreciated.

 

[Davidasailor26]

Maybe a blockage in the sea water intake? Does water come out the thru hull when the seacock is opened?

 

[Kings Gambit]

You might have sucked up something into the water intake. I’ve noticed the change in sound tone when that happens to me 3JH3E.

 

[smokey73]

Did you get a chance to check the engine visually when you got the high temp alarm but before you saw the billowing "smoke." 20/20 hindsight but as a general rule it is a good idea to shut the engine off immediately upon a high temp or low oil pressure alarm and try to get to a safe place to anchor or put up the sails if there is any wind at all unless in imminent danger of collision but that is a hard thing to do when in a busy seaway.

If you smelled rubber I'd be more apt to suspect a loose belt or seized bearing since from your description, you smelled the rubber smell before the high temperature alarm. Neither of these would impact the raw water coolant pump since I believe it is gear driven. However, the coolant pump is belt driven. Could be a seized bearing on the alternator or the coolant water pump. Did you inspect the belt and the coolant pump? Is the belt loose or damaged? With the belt off, can you spin the coolant water pump pully and the alternator pully by hand? Was it actually smoke or boiling coolant vapor? Did it smell like antifreeze or rubber? When you say "odd rubber smell" maybe it was actually antifreeze smell from the blown off coolant cap. At 71 I've had a lot of cars and a diesel engine or two overheat but I don't ever recall the coolant cap "blowing off" Think back through the indicators and sequence of events.

Is it possible you sucked something up into the intake like a fish or possibly a piece of plastic? Still wouldn't explain the rubber smell as it started to heat up before the high temp alarm though. It is a puzzlement>

 

[smokey73]

Description of "timing" of events might help pin down the problem. How long from the odd rubber smell to the high temp alarm. 1 minute or several minutes? How long from throttling down until you noticed the "billowing smoke."

Please don't take offense at the "20/20 hindsight" comment. Just a note for all of us to have a plan as to what we will do if we get such an alarm. I've had one too and the decision was not easy under the circumstances that I was in at the time. Wind blowing, 2 knot current, sails down, 100 yards from the mooring ball in the middle of an crowded mooring field with chance to blow down on boats, no time to get the sails up or anchor out Not enough way on to coast to the mooring ball. CRAP! I gunned it for a few seconds to get some way on, coasted to the mooring ball and grabbed the floating mooring ine as I passed by with too much way on and almost got pulled off the boat before I could get the line on a cleat and then changed by pants. There are always choices and the choice depends on the circumstances and we weren't there so no judgement here.

 

[flightlead404]

No wind busy seaway let’s not get distracted by discussions of how I handled it
Verified the following this am:

• She’s strainer clear and clean, water pours in from through hull
• All hoses from sea strainer to and including exhaust elbow clear and clean
• Heat exchanger clear
• Blown air or water through and visually inspected above, some replaced in last month
• Impeller new and good
• Removed raw water pump turns freely, its a hundred hours and 18 months old
• I see zero reason why no raw water exiting exhaust

 

[flightlead404]

Could something have happened in the accessory case to the gear driving the raw water pump? Seems unlikely especially since the engine didn’t grenade

transient blockage of through hull, plastic bag or fish? Grasping at straws now

 

[MikeHoncho]

The smell was either the belt slipping not allowing the pump to turn or the exhaust hose overheating . I’d make sure the exhaust hose isn’t damaged before moving forward

 

[kloudie1]

I think, as Mike that the rubber you smelled was the exhaust hose which lost cooling when the water stopped. The inside of the hose may have choked off when that happened to the point where the engine exhaust pressure blocked the seawater pump discharge.. (straw grasping) If you pull the water hose at the exhaust ell (very briefly) with the engine running, does water freely flow from that hose?

 

[flightlead404]

I did find a small amount of ferrous metal inside the bore the raw water pump sits in. See pic. Teeth of the drive gear feel a bit rough but the teeth on pump fine.
Concur the “smoke” was mostly steam with maybe some hot engine grease and dirt as well. Rubber smell

 

[flightlead404]

I am completely at a loss. There is no blockage anywhere from end to end. Removed the raw water pump again, it spins freely and the shaft is not broken or seized or anything, yet it appears it is not turning with the engine.

took a picture of the impeller, started and ran engine for a few seconds, no sign of water. Checked the hoses from output of pump to heat exchange, all dry. Checked the position of the impeller, it has not moved!

WTF

 

[smokey73]

Just saw the last post. I deleted my last post as it is overcome by post 11. Seems you have narrowed it down to the geared drive from the engine to the pump. It sounds like the gears at the pump end are good. Hopefully you have a parts manual or can get one so see what drives that gear. Maybe the shaft is sheared or whatever connects to the engine at that end is stripped? Again, best of luck. No idea how to check that.

 

[flightlead404]

Cranked engine with cover plate off pump. Confirmed shaft is not turning. Anyone with real knowledge of this engine know if there is some sort of shear pin perhaps on the drive gear in the accessory case?

 

[smokey73]

Looks like there is a key (part 17) in the drive shaft for the water pump.

Yanmar Shop - FIG 16. COOLING SEA WATER PUMP Schematic

View detailed interactive schematics and parts lists for FIG 16. COOLING SEA WATER PUMP at Yanmar Shop

yanmarshop.com

 

[flightlead404]

From service manual, pump is gear driven directly off camshaft gear. If camshaft gear was not turning engine wouldn’t run. I’m at a loss

 

[flightlead404]

Looks like there is a key (part 17) in the drive shaft for the water pump.

Yanmar Shop - FIG 16. COOLING SEA WATER PUMP Schematic

View detailed interactive schematics and parts lists for FIG 16. COOLING SEA WATER PUMP at Yanmar Shop

yanmarshop.com

looks like that key is to stop the pump gear rotating on the end of the shaft.

holding the pump gear in one hand and the impeller in pliers with the other I cannot rotate them with respect to each other. when I suggested a shear pin I was thinking on the drive gear in the accessory case but it turns out that it is driven by the camshaft gear which is obviously turning or the engine would not run

 

[flightlead404]

Shit!

with pump installed I can rotate the shaft easily, and can feel “bumps” like gear teeth touching as they pass. Pump gear looks fine. Ordering a new pump just in case but I’m guessing at minimum camshaft gear is worn since it won’t engage.

 

[flightlead404]

Pics of pump gear and camshaft gear. These wear patterns indicate to me that the gears were barely engaged.

Checking depth on the pump gear it’s 28.7mm from the face of the mounting flange to the back of the gear, approx 17.07mm to the front of the gear where the wear appears.

On the engine from face of accessory case to front of gear 28.21mm and 44.41mm approx to rear of gear

A HALF A MM OF ENGAGEMENT!!!!!!!!

No wonder there’s an issue, wrong pump?

As an aside I questioned if I should bother packing calipers as part of my traveling tool kit, but they don’t mass much so I did. Glad I made that decision.

 

[kloudie1]

Good catch ! Yup, I have a precision caliper in the tool kit.

 

[smokey73]

Ouch! Best of luck. Hopefully you got a tow to the nearest place where you can get to a good diesel mechanic.