Lost Cooling Water Flow

[Chuteman]

Visiting a friend (really it's not me) on his '89 Catalina 42 with a Yanmar 4jhb
(yes, the b is accurate). He was doing maintenance & changed the raw water impeller. After starting (and idle 10 mins), water flow was fine, motored out for about 20 mins everything was fine, then sailed for a couple of hours, quick engine use (5 mins) - water flow fine, more sailing.
As we started to approach marina, drop sails, etc - engine started but no cooling water output from engine.
Checked all the usual stuff and even pulled the impeller again - it looks fine.

Any hints?
P.S. did quick search & did see one possibility - will head back & search more.

[svHyLyte]

Obstruction in the raw water intake.

[Pblais]

Air leak on the hose connections. I had that this year. Checking the impeller was the first step and should be fine. Can you shove a garden hose in the raw water strainer and blow it out the through hull OR run the engine. A hose will find a physical blockage yet not show an air leak.

[Tellie]

Check for air leaks and obstructions to be sure.
If that fails change the impeller. Some impellors have a bronze bushing bonded to the impeller blades. That bond can beak free and the bushing spins but does not turn the impeller. When you open up the pump the impeller looks fine and some people go crazy looking elswhere. Just a thought.

[Chuteman]

Thanks guys..........will do suggested items.

Update - after sleep & breakfast we bumped the engine to make sure the pump(gear driven) was still Ok........it is.

Blockage - at 1st look yesterday when it 1st happened - the water strainer/collector was only down an inch or two - not dry.........but will still do blockage / blow out test

Impeller Bronze - Thought of that - it was "brand new" and the bond seemed ok via finger test - is there another way to check without tearing the bronze? Headed back to get another new impeller to make sure plus getting them out always leaves "marks"

[Tellie]

Originally Posted by Chuteman

Thanks guys..........will do suggested items.

Update - after sleep & breakfast we bumped the engine to make sure the pump(gear driven) was still Ok........it is.

Blockage - at 1st look yesterday when it 1st happened - the water strainer/collector was only down an inch or two - not dry.........but will still do blockage / blow out test

Impeller Bronze - Thought of that - it was "brand new" and the bond seemed ok via finger test - is there another way to check without tearing the bronze? Headed back to get another new impeller to make sure plus getting them out always leaves "marks"

Usually I start with the last thing I fixed, first. In this case it was the impeller. If you changed out the impeller and the water flow stops shortly there after my guess is that's where the problem lies. About the only way I know how to check the bond is put in a new impeller, unless of course the bond is really shot. I've had two brand new impellers do the same thing on my boat. If this is not the problem at least you know you have an extra impeller that fits. Always good to have an extra on board all times anyway.

[Chuteman]

Tellie:
Agree - absolutely.
New Impeller is being picked up as I type. The crazy thing is that it worked at least 1/2 hour - 45 mins total time after installation then stopped.........so we'll start from the beginning with the suggestions made.
Also going to change out the hose from the strainer to the pump as it could be better - just to be sure.
Thanks again

[Tellie]

Just a quick note. A small amount of GLY on the blades before installation goes a long way.

[David M]

I coat mine with silicon grease before installation. Any sort of petroleum based product can adversely affect the rubber....like Vaseline. Frequently, it makes the rubber swell. You can get silicon grease at dive shops.

[anjou]

Most water pump impellers are an interference fit on the shaft and once in a while, they can come lose.

Dont be tempted to over tighten the belt as its the most common reason for water pump and/or alternator bearing failure

[anjou]

Do you have a thermostat capsule in the system anywhere?

[Chief Engineer]

If the impeller was changed.....there may be a piece of blade downstream.

[Chuteman]

Happy Ending - at least so far.

Installed
New Strainer to Pump hose
New Impeller
Small Hollow Flat Clip with teeth that was left out when the impeller was changed Sat - stuck on old impeller.......it goes on after impeller is installed - fits in shaft hole.
Small flat solid cap that also goes in shaft hole on top of clip
Black rubber ring "gasket" that fits in pump outer groove before cover goes on
BTW - the marine store only had some of these individual pieces. It would be nice if they had the "kit" as an option - the search for that is now on

Magic = it worked........

Also blew back thru strainer to make sure nothing was clogged in seacock. Tightened everything down. Before starting engine = Opened seacock which allowed water to fill strainer, hose, pump and even hose past the pump as we opened a bleed fitting (with long small drain hose attached) on the rear of the engine..........we closed once the water came thru.........so it was "primed". Cranked engine & cooling water was flowing again.

Guessimate = combination of not having that little clip in place inside the pump & an air leak.......

anjou - not sure what you mean by interference fit - this one had a bronze grooved center that fit on the pump shaft splines.........and BTW the pump was gear not belt driven.........it definitely looked different than the smaller Yanmar engine I had a water pump adventure with but that's another story..............also not sure what a thermostat "capsule" is

CE - Both the old & Saturday Replacement had all their blades in place & there has not been any history of blade loss on this water pump/engine.

Thanks Again to all for the quick and knowledgeable responses. My friend appreciates the help - maybe I can get this experienced sailor to join CF to pay it forward.
I leave this weekend adventure on an am flight - so maybe that will help keep the water flowing too.

[Tellie]

I cheated and copied and pasted. It was better than the way I tried to explain it.

An interference fit, also known as a press fit, is a fastening between two parts which is achieved by friction after the parts are pushed together, rather than by any other means of fastening. For metal parts in particular, the friction that holds the parts together is often greatly increased by compression of one part against the other, which relies on the tensile and compressive strengths of the materials the parts are made from. Typical examples of interference fits are the press fitting of shafts into bearings or bearings into their housings and the attachment of watertight connectors to cables. An interference fit also results when pipe fittings are assembled and tightened.

A thermostat capsule. I beleive she is refering simply to the thermostat. A thermostat capsule can encompass many types of thermostats. We used to use bi-metal capsule thermostats in electrical work as well.
She did also make a very good point about over tightening your belt. On your engine the waterpump it is gear driven but it is a good point to remember for any belt on any engine.

[anjou]

Well everyday is a school day as ive never heard of a gear driven water pump.

Next time im near a yanmar i shall be looking out for it.