Impeller Issue

Maine Sail · Feb 27, 2012

mattkling said:
Maine Sail-

I have a Beneteau 361 and have torn a fin or 2 on my impeller two years in a row. Quite costly to dig those buggers out of the system and caused overheating issues last time around. Impeller is a pain to get to on the Westerbeke and nearly impossible away from the dock.

There are plastic external stainers over the inlets on the bottom of the hull - could they be hindering water intake and causing the impeller to heat up and break? I scraped all the bottom paint from between the "bars" when it was hauled last summer. Looked clear inside the "cage". Not sure how easy they would be to remove or if I should?

Thoughts?

Johnson impellers are quite famous for a 1 year service life. I am in the change it every year camp, regardless of pump manufacturer. Diminished flow can cause issues and I am not a big fan of external strainers but you should still plan on annual changes..

Kettlewell · Feb 27, 2012

I've found the blue-colored Globe "run-dry" impellers last longer, though I still recommend a change every year. Cheap insurance.

Steve Dion · Feb 27, 2012

Matt:

Have you ever considered a SpeedSeal? Check it out. I don't know if they have one for your engine but it does make r/r easier and the new type is supposed to increase impeller life!?%$#@*

http://www.speedseal.com/saferboatindex.html

They may sell them at SBO too.

Kettlewell · Feb 27, 2012

Yes, I have a Speedseal and can endorse it. It does make changing the impeller easier, but not easy. At least on my boat access to the area is very difficult.

Warren Milberg · Feb 28, 2012

If you are tearing off a blade on your impeller every year, my guess is that you are either (1) sucking up sand or grit from backing off a grounding, or, more likely (2) you have a rough edge on the cam or inside the housing of your water pump. I would also check to make sure the cover of the water pump is smooth and is seated properly on a gasket when the pump is closed.

I have a strainer on the raw water intake and believe it has saved the day for me many times over the years in terms of debris/leaves/plastic bags/string, et al, it has kept out of the water intake side of my engine. It is easy to keep clean and free of bottom paint during spring maintenance.

Rich Stidger · Feb 28, 2012

A question for you Speedseal users-

I looked at the info on Speedseal LIfe. The disk bearings inside the cover plate look like they could be effective, but what about the inside of the pump on the other side of the impeller?

Doesn't the impeller wear on both sides? If the impeller is run dry, I would think that the impeller would still get ripped up due to the friction from the inside of the pump opposite the cover plate.

Comments?

Rick D · Feb 28, 2012

Speedseal

Rich Stidger said:
Doesn't the impeller wear on both sides? If the impeller is run dry, I would think that the impeller would still get ripped up due to the friction from the inside of the pump opposite the cover plate.Comments?

I have the old Speedseal before the wear disk was added. There are some wear marks on the stainless cover, but it's almost like a fine polishing. Don't recall seeing anything like that in the housing face. But, regardless, based upon about a thousand hours on the seal, hard to see why a disk would be necessary.

BTW, I wouldn't recommend the seal necessarily for a 40.5. It isn't much more difficult to remove the stock cover. I find I have to use a pliers to loosen the thumb screws anyway. And, the real hassle is getting the impeller out anyway. A better purchase is a small impeller puller.

I used to go through impellers on my 3GM Yanmar much more commonly than the 40.5. I suspect it was the very small intake and its propensity to be blocked by very small floating debris. I changed the impeller every season and still found it without all the vanes a few times. Once I had to replace it mid-season and open up the front of the exchanger to fish out the vanes. I suspect that one was a bad blockage due to some build up of tiny muscles.

JoeWhite · Feb 28, 2012

I am in the process of changing my raw water pump. In reading the posts above - is not there some kind of filter or strainer available that can be added after the pump and before the heat exchanger so that it can catch the broke impeller blades? I am thinking to add such a device.

Rick D · Feb 28, 2012

Good Thinking...

JoeWhite said:
I am in the process of changing my raw water pump. In reading the posts above - is not there some kind of filter or strainer available that can be added after the pump and before the heat exchanger so that it can catch the broke impeller blades? I am thinking to add such a device.

...but it would be my opinion it isn't worth the trouble. First, it isn't that common; second, you would still have to get to the strainer; third, it isn't all that hard to pull off the exchanger end to fish them out anyway. At least, that's how I'd look at it. Regardless, good thinking.

Rich Stidger · Feb 28, 2012

mattkling- You asked about cleaning and/or replacing the external slotted thru-hull. Below is a picture of one of mine and you can see the barnacles inside of it. Mine was a one-piece design meaning that the slotted external strainer is connected to the thru-hull threaded pipe. It all comes out as one piece.

My experience- I have three thru-hulls in my boat that suck in water for the engine, genset, and A/C. All of them have big Groco strainers on the inside and for years these would occasionally plug with seaweed and an occasional jellyfish. I have burned up my share of impellers over the years due to these plugs. The two intakes that supply my engine and genset had no external strainers and the slotted strainer was only on my A/C inlet. The two engine strainers were in a really bad location and a PITA to check. Additionally the slotted thru-hull was very hard to clean-out and I could not get any anti-fouling up into the thru-hull to discourage the growth.

A couple of years ago I changed the A/C slotted one-piece thru-hull to a standard one. Over all three thru-hulls I installed external strainers with a hinged cover. These are made by Groco. The advantage is that with holes instead of slots it is much harder to get seaweed to enter and travel to the Groco basket strainer inside. Since installing these external hinged-cover strainers, I have not gotten more than 2-3 pieces of seaweed into my basket strainers in an entire season. The result is no plugs, no decrease in water flow, and no impeller failures from lack of water. With the smooth surface of the holed-cover, I also have not picked up any plastic bags, jelly fish, or any other floating debris.

I realize that Maine Sail does not like external strainers and I respect his position, but they work for me. In the Spring I open the covers and clean anything that is inside. Since I can paint anti-fouling inside, I rarely have anything to clean. The main point is that they are actually cleanable.

JoeWhite and RickD- I think the additional strainer to catch impeller pieces is a swell idea! Maybe it is un-necessary if you can easily pull the HX cover off, but in my case accessing the HX cover is very difficult. I actually have an impeller fail with broken pieces every couple of years, so I my case it is relatively common. I will admit that maybe changing the impeller every year as Maine Sail advocates could likely eliminate those failures. Currently I change impellers by number of hours run. I have seen impeller failures at the 300-350 hour range so I change at 250 hours. Regardless, maybe it is still a better idea to just change annually.

Maine Sail · Feb 29, 2012

Rich Stidger said:
I realize that Maine Sail does not like external strainers and I respect his position, but they work for me. In the Spring I open the covers and clean anything that is inside. Since I can paint anti-fouling inside, I rarely have anything to clean. The main point is that they are actually cleanable.

What I dislike are slotted permanently installed power boat strainers, often installed backwards on sailboats, that are near impossible to clean.

The proper strainer for a sail boat is what you show, non-directional, opening and with holes as opposed to slots. If you do need to clean it you can dive and open it. I still prefer to ream out from inside but if access is an issue the Groco non-directional opening strainers are the way to go..

These boaters incurred expensive haul outs $$$$$ due to clogged external strainers. If they had the Groco's they could have easily been cleaned out in the water..

Impeller Issue

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