Heads Up w/Impellers on Yanmar

DrB · #1 (**permalink**) 08-11-2008

Thought I'd pass along a potential info tidbit that I learned while sailing on my cousins boat a a few days back.

We motoring up to Annapolis because of the lack of wind and all of a sudden the motor stopped producing exhaust water and the exhaust went black. Emergnecy shutdown and then we went below to acertain the problem, while the wives rolled out the jib and saied the boat.

Sea strainer had some weeds in it so we cleaned it out, but we didn't think it was much. We restarted the motor and waited 30 seconds and no water. Shutdown the motor and checked the impeller. Everything looked fine, so I thought it was the muffler or mix elbow that was clogged.

To make a long story short, the impeller was actually shot. Although it had all of the vanes and looked good, the metal bushing had sheared away from the rubber so that while the impeller shaft was turning, the actual impeller was not. I would have never thought of this, but my cousin got the local Yanmar guy on the line and said what often happens is that sea water flow stops and without it the lubrication to the impeller vanes stops. Once the lubrication stops, it doesn't take much for the rubber piece to shear away from the shaft bushing. So while it looks fine, it is not. Even a small or momentary interruption to the coolant water flow can casue this according to the Yanmar rep.

Something to think about if you motor stops "peeing" out the back for any period of time.

DrB

Pamlicotraveler · #2 (**permalink**) 08-11-2008

Quote:

Originally Posted by DrB

Emergnecy shutdown and then we went below to acertain the problem, while the wives rolled out the jib and saied the boat.

So the wives were able to sail when you couldn't....That's impressive.

Your point about the impeller is a good one. You don't want to wait until they break apart, or run the tngine for long enough to allow that to happen. If they weren't in such an awkward position to change I would change mine much more regularly. I don't know why they can't put the impellor access on the outside of the engine...

DrB · #3 (**permalink**) 08-11-2008

Quote:

So the wives were able to sail when you couldn't....That's impressive.

On my cousin's boat, I believe that often the case is when the sailing speed drops below 3 kts, the motor goes on. For this particular incident, since there was no motor, the only "alternative" was to use the sails to move the boat. So it's not that we couldn't sail, we couldn't sail "fast enough".

DrB

bruceyp · #4 (**permalink**) 08-11-2008

I had the same experience on my Yanmar. Everything looked good at first but upon closer inspection the bushing was spinning in the rubber. I keep 2 spares on board and start every season with a new one.
BP

danielgoldberg · #5 (**permalink**) 08-11-2008

Quote:

Originally Posted by Pamlicotraveler

If they weren't in such an awkward position to change I would change mine much more regularly. I don't know why they can't put the impellor access on the outside of the engine...

That drives me absolutely nuts! On most Yanmar installations you need to remove a motor mount to get to the raw water pump, and thus the impeller. What were they thinking, and why on earth don't they change that?!

The Beta Marine engines actually have everything, including the raw water pump, accessible from the front of the motor. That's such a brilliant, and obvious, idea that I'm amazed every manufacturer doesn't do it.

DrB · #6 (**permalink**) 08-11-2008

My Yanmar has the raw water pump on the outside of the motor and it is somewhat easy get to. I don't really have any issue. My cousin's was easy to get to also, although it was on the side instead of the front.

DrB

jbondy · #7 (**permalink**) 08-11-2008

When I replaced my 3GM30 with the newer 3YM30, one of the purported benefits was an ergonomic redesign. Now all the things we need to access are on or near the front of the engine. That's fine, except I've got a v-drive, so the "front" of the engine is aft, deep in a cockpit locker. I have to hang upside down like a bat to check the oil, and don't ask what I have to do change the impleller! I guess you can't please everyone.

Joesaila · #8 (**permalink**) 08-11-2008

We were heading out on vacation last week and started the motor to warm it up. A red light came on [overheating!] and I noted 0 water coming out of the exhaust. Checked the sea water strainer, it was clear and then removed a few bolts to lower the water pump. [Yanmar 27hp] Most of the impeller blades were shot so I dug them out and was fortunate to have a spare on board. Then we went on a week long sail. I'll follow the old rule of thumb and change it yearly now. But I do appreciate that tip on the bushing coming off.

Mikelivingstone · #9 (**permalink**) 10-15-2008

It seem like this is what happened to my impellor this weekend. Why does this happen I had changed my impellor about 2 months ago ( and it wasn't cheap)??

Giulietta · #10 (**permalink**) 10-15-2008

The impellers are not made by Yanmar, mine are made by Johnson pump, and have gone thru 2 already..and keep a few spares...my only worries is it happening in a moment you really need the engine..It's not really yanmar's fault..I guess...I change every year, need or not...the ones I take away every year serve as spare...in case.

If I could find a better impeller brand that would help..if you guys know of a better one...please tell me.

My access is pretty easy..close saildrive water intake, open 4 bolts, put new one in..all takes me about 4 minutes...open valve (very important)..ehehe

Photo shows my impeller compartment thing cover lid..