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What does the instruction book say?
 

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Just me, but I check for water flow in the exhaust at every startup (as we all should) and then periodically throught the motoring evolution. Once a year, I take off the cover of the pump and visually inspect the impeller. Not just a "yep there it is", but get down close to it with a flashlight and mirror and look at it up close. I look for signs of wear... small stress cracks, missing corners, severely worn blade tips. Then if required, take the impeller out and clean the inside of the pump (crusty buildup etc). Make sure you put the impeller back in correctly (use soap water for lube).

I do have many years as a marine mechanic under my belt, so I know "it's time" when I see it. If you do the above, you'll be OK. Dave's .02. ;)
 

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I take a look at the one on my boat once a year, and replace as needed (about every two or three years). When I take it out I flex all the vanes and look closely for any cracking. At the first sign of any problems we replace it. If it looks OK I coat it with a little silicone lube and but it back it. We also check for mineral deposits/scale/crud in the rest of the cooling system (the parts we can get to, anyways) at the same time.
 
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I change mine once when commissioned in the spring and again when it fails in the middle of the summer. This is my tale of woe:

http://www.sailnet.com/forums/gear-maintenance/89516-premature-impeller-failure-cause.html

My best guess is that the pump is undersized for the engine. Just a poor design. Although the engine drawings indicate 1" hose the fittings for the pump are 5/8 or 3/4 (forget now). My repowered Weterbeke 55 uses the smallest Johnson pump, a F35. The Westerbeke 46 that it replaced used I believe used an F5 or F6. Just to make it more fun you can't change the impeller with removing the pump because of the location.

This winter I'm going to go with a F5 crank pully mounted pump that should make changing the impeller a piece of cake and hopefully eliminate the failure issues. The new pump is roughly double the capacity of the old but will be spinning at 80% of the old pump at any RPM. I'm going to further reduce the pump capacity by using a smaller pump cam which according to Johnson should reduce the flow by 30%-40%. I'd like to get slightly more flow with a larger slower spinning pump.

Sorry for hijacking the thread. Saw an opportunity to vent a little.
 

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I've read this question many times over the years. It basically seems to fall into 2 groups:

1 - replace every year
2 - we never replace it

I carry a spare, but have never replaced one on the boats I've owned. My current boat is running around on a 13 year old impeller in an engine that has 920 hours on it. I'm sure people in group 1 will say my engine is about to burn up, but my last boat had a 22 year old engine with 2200 hours and it still had the original impeller.

My manual says to replace every 6 years or 1000 hours. So I'm considering it for this winter.
 

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I've read this question many times over the years. It basically seems to fall into 2 groups:

1 - replace every year
2 - we never replace it

...
Option 2 (which should probably be called "don't replace it until it fails") runs the risk of a vane breaking off and getting lodged somewhere downstream. Not a good thing.

As I posted above, I'm somewhere between your two extremes; I take a close look at the impeller every year and if it doesn't look pristine I replace it.
 

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I've read this question many times over the years. It basically seems to fall into 2 groups:

1 - replace every year
2 - we never replace it

I carry a spare, but have never replaced one on the boats I've owned. My current boat is running around on a 13 year old impeller in an engine that has 920 hours on it. I'm sure people in group 1 will say my engine is about to burn up, but my last boat had a 22 year old engine with 2200 hours and it still had the original impeller.

My manual says to replace every 6 years or 1000 hours. So I'm considering it for this winter.
I'm happy to see others that don't change it. I never have, but always check for water out the exhaust. We've put about 1000 hours on our old 3 GMD in the last two years, and cruised 5000 miles. No problems yet. I'll replace it before we head out again. It's probably due.

Ralph
 

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I'm firmly in the every year camp. By the time you go through the trouble of pulling the impeller to inspect it, you might as we'll replace it. Impellers are cheap. Monitoring the impeller by watching the water flow makes no sense to me. When the water stops flowing, you already have a problem. And it's likely to occur at the worst possible time, just when you need the engine. (Note: I still monitor water flow)

I realize that I'm likely changing the impeller more often than necessary, but I figure it's cheap and easy preventive maintenance.
 

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Being a seasonal boater, I change it before start up each spring. I've had numerous impellers fail over the years, even with this process, so I truly don't understand those that wait. You can not know that something didn't temporarily block water flow, while you were underway at some point and heat up the impeller. Even more likely in my book, I swear the yard tards have started my motor to do work and forgot to open the seacock. 1 min to test for an oil filter leak would weaken it considerably. I know this has happened!! The deny it.
 

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I'm firmly in the every year camp. By the time you go through the trouble of pulling the impeller to inspect it, you might as we'll replace it. Impellers are cheap. Monitoring the impeller by watching the water flow makes no sense to me. When the water stops flowing, you already have a problem. And it's likely to occur at the worst possible time, just when you need the engine. (Note: I still monitor water flow)

I realize that I'm likely changing the impeller more often than necessary, but I figure it's cheap and easy preventive maintenance.
Part of spring commissioning every year. Did you ever try and find all the vanes in the heat exchanger.
 
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My experience has been somewhat different in that after a few years of not changing the impeller, I decided that it was time to put a new one in. After doing so and applying the proper lubricant, I had troubles with the water flow. Come to find out several of the vanes had broken off after only a few hours of operation. I came to the conclusion that the lubricate that I used must have been incapatible with the impeller. Now I use only soapy water, but still that episode makes me less likely to do annual changes. I think part of the problem with impellers is how the boat is winterized and what type of antifreeze is used. I use an engine antifreeze to put in the raw water side and that probably has better capatability with the impeller than the pink stuff or even leaving it dry.
 

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Mine works fine, but I'm wondering about the frequency of changing something that is working.
I have not had to change mine in over seven years. But, that's because I converted to Electric Propulsion and changing the impeller was just one things I no longer had to deal with. ;) But, when I did have a diesel on board I would forgo replacing the impeller because it was such a PITA to access it. Had to pretty much do it by feel. So several years was the norm. But, if I had better access I would remove it over the winter and/or replace it every year. But, that was not the case with my engine orientation.
 

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Ever notice that people who change their impellers every year report more broken impellers :p
 

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I have not had to change mine in over seven years. But, that's because I converted to Electric Propulsion and changing the impeller was just one things I no longer had to deal with. ;) But, when I did have a diesel on board I would forgo replacing the impeller because it was such a PITA to access it. Had to pretty much do it by feel. So several years was the norm. But, if I had better access I would remove it over the winter and/or replace it every year. But, that was not the case with my engine orientation.
Mike, if you had a Westerbeke W-27 V drive, then we have/had the same engine. The PO of my boat installed a speedseal and it makes it much easier to access the impeller.

I hope I get to see your electric drive in person some day. Sounds like quite a set up.
 

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Propylene glycol is a leading cause of premature death. Neoprene impellors (most) are NOT compatible with the pink stuff. The manufacturer will tell you this, you can Google it, and I have done side-by-side testing. Ethylene glycol (engine coolant) does not have this effect.

Do not winterize raw water systems with PG.
 

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I have three years on the same impeller and there are still no signs of wear. Every winter, after winterizing the engine, I spray the impeller with silicone oil, just to be on the same side. Works for me.

Gary :cool:
 
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