Shredded impeller

[Stella Polaris]

I should have known better, but still managed to fire up the engine and then jump in for a refreshing swim while it churned away on a good rpm for about 15 min before I noticed: no cooling water. I stopped the engine (no overheating alarms) and opened up the water pump to look at my impeller. All the wings were either gone or severely damaged.

I found a little plastic in the tube leading away from the waterpump, but need to unscrew more in order to find the missing pieces to my impeller puzzle.
I have 2 questions:
- Does anyone have experience with the Yanmar 4JH5E or similar engines, or tips in general, that could help?
- How much of the missing impeller do I need to find? (Is there cause for panic, if I can't find all of it?)
Any insight would be greatly appreciated!
- Andreas

[Captain Bill]

I have a 3jh3 and I find most of my impeller parts in the heat exchanger when they go. Find all of it if you can as the parts will block the tubes in the heat exchanger. It might be ok at low power settings with a few tubes blocked but at higher power it will overheat. You can probably guess how I know.

[pcmm]

You should try to find all of the bits if you can. the more bits in the heat exchanger or other hoses, the less cooling water will flow due to blockages. sometimes I wonder why there isn't a strainer AFTER the pump to catch bits like this! it shouldn't be too hard to take apart the hoses that are the seawater side of the cooling system and look for the bits.

[svHyLyte]

Ah... You need to find and remove ALL of the parts to your wasted impeller. You might find that the easiest method is to disconnect the tube between to discharge side of the heat exchanger and the exhaust mixing elbow injection nozzle; and, the tube between the discharge side of the raw water pump itself and back-flow water through the heat exchanger toward the pump with a hose connected to shoreside water in hopes of dislodging the impeller's bit'n pieces. You need to get them all out. It would also be wise to take a look at Dockhead's thread on impellers, which has been going for the last several daze. Good luck!

[boatbod]

Follow the plumbing. Most impeller parts will be stuck at the next device in the chain (I.e. Heat exchanger). Some may have backed into the intake hose. If you have one available you can try back flushing with a dock hose, otherwise pull the end cap and take them out manually.

[MarkJ]

They are in the front of the oil cooler.
Look at the rear of the engine above the transmission and you will see a tube 8 inches long, 1.5 inches in diameter. Pull off the hose and pick them out with tweezers.
Put the jigsaw puzzle back together and check you have them all.


That's for a 4JH3E. Should be the same with yours

[Stella Polaris]

Thanks guys!
I'm on the hook, so I don't have access to pressurized water I could back-flush with (unless I want to empty my water tanks). I will definitely try to find all of the missing impeller pieces. My gf will be so "happy" that I'll be putting her tweezers to proper use!

[DeepFrz]

If you don't find all of the bits in the heat exchanger then you will have to check the exhaust elbow.

[shakey doug]

A surprising amount will have passed through the system, also check down the low pressure side of the pump plumbing some times a lot will go back there.

[ranger58sb]

In the meantime, be thinking about what caused it... so it doesn't happen again. Sea cock closed? Old impeller? Or...?

-Chris

[svHyLyte]

Originally Posted by Stella Polaris

Thanks guys!
I'm on the hook, so I don't have access to pressurized water I could back-flush with (unless I want to empty my water tanks). ....

Buy yourself a submersible bilge pump, connect the discharge to a length of hose connected to the discharge side of your heat exchanger and place the pump in a 5 gallon bucket of fresh water. Jumper the pump to your batteries with alligator clips and you have pressurized water. Attach another length of hose to the input side of the heat exchanger, direct the discharge through a colander and back into the bucket. Once you've got all the bits and pieces out, refresh the water in the bucket, add a quart of Barnacle Buster and recirculate that for an hour or so and you'll have a clean heat exchanger to boot. Save the rig for future use.

FWIW...

[a64pilot]

If you install a strainer right after the pump, you will never have to look for impellor bits again

[SKI]

I've had this happen on my inboard ski boat before. My thought was to make a filter to catch all the bits ( Think inline fuel filter type) Something with barbed ends on both sides then threads apart in the middle with a piece of perforated aluminum screen. They would be made completely out of 6061 Aluminum and hardcoat anodized to protect against saltwater. It would be easy to figure out how much to upsize the screen area so no restriction occurs. Basically cut say 2" out of your hose in a easy to get to spot and just hose clamp it in. I own a CNC Machine shop so this could be a good project for us. I always thought it would be a good idea but I wonder what others think and weather it would be something they'd buy for say $70-80.

[HopCar]

Originally Posted by a64pilot

If you install a strainer right after the pump, you will never have to look for impellor bits again

I don't understand why engines don't come from the factory with a strainer there. It's just so logical.

[leftbrainstuff]

Pays to backflush your heat exchanger. Filter the outflow. If you're lucky enough to find all the bits then you can stop.

We change our raw water impeller once a year or at the oil change whichever comes first.

We rarely do more than 150 hours a year on our main engine.

We do have quite a few used impellers. For the price I'd rather swap them out than have to do an unplanned change.