Stupid Stupid Stupid on H320

[Deadline]

When I went to launch, I stupidly forgot to open the raw water seacock.
Yet the engine performed fine for entire 20 minutes to the slip, at 2000 rpm.

Thought I had ruined the impeller, but it's fine. Yet anti-freeze is still there!
I resealed the Johnson water pump with black goo and the O ring.
Still, there doesn't seem to be any outflow. Exhaust is below the waterline.

This is a Yanmar 18 2GM20F with 700 hours.
How can it run without raw water going through it?
It's not a thermostat issue, since that's the coolant side of the engine.

It seems like cavitation, in which air is seeping into the water pump.
Should I use a paper seal instead of black goo?
I once used both and THAT caused explosive cavitation.

Any advice? Very frustrating. Thanks.

 

[navigator97]

I would only use the 'paper' Yanmar gasket without any 'goop' on it. Also make sure that the metal cover plate is clean and free of ant buildup or gauges. If is not cleanable to a good and flat surface, then replace it and probably the small set of screws. Make sure that the housing mating surface is also clean and flat. Another wear point is the 'Cam' that is screwed down indide the housing. That has to be replaced periodically. If it hasn't been replaced in the 700 hours, then it probably should be. It wears over time and causes deflection of each impeller blade as it passes over it. I have replaced my Cam twice, the cover plate once and the gasket every time I open the raw water pump.
R.W. Pump Parts are:
Gasket #124223-42116
Cover Plate # 121575-42150
Cover Screw set M4x8 #26554-040082
Pump Cam # 124323-42100
Cam Screw M4x10 #26544-040102

 

[Bill Roosa]

Ditto the "don't use goop" comment as the clearance between the impeller and cover plate is key to it creating a suction. If you have a gap between them it just does not preform well. this is especially true if the pump body is above the waterline.
You can check by pulling the hose off the suction side of the pump and feeling for suction with the engine running.

 

[Ken13559]

Sometime airlock will prevent pump from working. Suggest you disconnect pump discharge side and pour water into the hose/pump to prime it. Put back hose and try running engine. I had same problem before. Also mine uses O-ring and not paper gasket. Don't like to use goo. Messy.

 

[Alex Dare]

First thing, I'd change the impeller. Even if it looks fine it may have taken a set on the vanes over the winter. In addition, if it's been run for any length of time w/o a free flow of water, you've killed some if not most of it's life. Forget the goop. The new impeller should some with either an o-ring and or paper gasket. You will use either the o ring or the paper gasket but not both. If it takes the o ring, there will be a groove in the cover plate for it. If not, it gets the paper gasket. The paper gasket (if used) will need to be aligned properly with the cover plate and cam on the pump.

The pump should be self priming so no need to prime it if all is working as it should. If you have a good seal on the cover plate and still suspect you're sucking air from someplace on the pump, it's possible the shaft seal is shot. Usually they'll leak though.


Next,
check both the inlet and outlet plumbing for blockage. You can try blowing through them first before you start pulling things apart.

 

[Benny17441]

There is a failure condition where the rubber vanes part will separate from the metal cylinder which drives the impeller causing the cylinders to spin but not the vanes. Under observation it may look fine but take it out and while holding the metal between thumb and fore finger try to spin the vanes. Another possibility is a flow blockage. Check your strainer.

 

[Dave602]

Hey Bill, Just re-did mine yesterday from a similar situation. I replaced mine and found the bushing was spinning in the rubber and the vanes didn't move. I use a thin film of gasket dressing with the paper gasket, it just helps to make the gasket sticky. Be glad to help you take a look.

Dave

"Up to No Good"

 

[Deadline]

Thanks to all for your advice as well as yard manager Ron Austin at York River Yacht Haven. It was probably cavitation from an air leak because the plate-to-pump fitting was too rough. It’s all fixed and ready to sail. For the next poor slob who has this problem, here’s a list of lessons learned.

• Collect parts and tools to replace the impeller.
• Check to see if raw water intake jar is full.
• Close the raw water seacock.
• Remove the water pump.
• Turn impeller to see if it’s spinning.
• If so, problem was impeller in first place.
• Clean and sand plate and pump housing.
• Make sure O-ring seating is clean too.
• Lube interior water pump casing with glycerin.
• Replace the impeller, turn slightly to seat it.
• Apply gasket shellac compound (not black seal).
• When that dries, seat the paper gasket.
• Try to keep the paper gasket dry.
• Reattach the plate, keeping paper gasket dry.
• Reload both hoses with water to avoid airlock.
• Reattach water pump and fanbelt.
• Open raw water seacock and fire up to test flow.

 

[Rich Stidger]

How did you prime both of the pump hoses?

 

[Dave602]

Glad you got going Bill. See ya out there

 

[Deadline]

Rich- I simply used a cup to pour water into each hose as I held as high as I could to retain water. Kept my thumb on the opening as I brought each hose down to the pump. At this point with the lid on, what little water that leaked did not wet the paper gaskey. And the leakage was minimal enough to create an airlock.