Raw water impeller (Yanmar 4JH4)

[Lee Hadjiosif]

How do you make sure that your impeller does not fail you during a trip? Do you open it up and check for cracks every so many hrs/months or is there an expected lifespan of the impeller? I can only get the gasket with the new impeller...so If I open it up for inspection I'm almost required to put in the new impeller. I would appreciate your thoughts and experiences. I know that the manual says 250hrs or annually but I wanted to hear from experience. I only put on about 50hrs annually. Thanks.

 

[sailme88]

The first indication of failure should be an obvious decrease in the volume of discharge water at the transom.. The sound and sight of the discharge is something that you should be familiar with. Next is your temp gauge. It should hold steady..

Paper gaskets are available without buying the impeller.. A google search should help you with that.

 

[RoyS]

You need to carry a spare (new not used) impeller on board. You should probably carry a complete spare pump and the tools to replace it at sea as well. As far as impeller life expectancy goes your own experience will determine that. I had an impeller failure during the third season of use with an average of 100 hours use each season. After that I replaced the impellers after two seasons of use and stopped worrying. This method of determining service life and replacement intervals can be applied to just about every component on your boat from exhaust elbows to fuel filters. The other method of determining when to replace certain components is to stress test. Hoses, for example, should be tugged on and bent to extremes not seen in normal service at the beginning of the season. Knowing that they survived such a stress test should give you confidence to sail another season. That coupled with frequent visual inspections should serve you well.

 

[BigEasy]

With only 50 hours of use annually, changing every year would be overkill. I have low usage on mine also and change it every 4 years when I flush and change coolant. Of course, I keep spares on hand in the event there is a problem. When I replace mine at four years, the impeller looks like new; again, I am not running the engine for long durations.

 

[Tom J]

Engine hours are only one criteria for determining impeller longevity. Another is shelf life. The rubber of the impeller can degrade over time, whether sitting on a shelf, or sitting idle in an engine over the winter. When I cruised down South, I would change the impeller around the 250 hour mark. Now that I sail seasonally, I change the impeller every two years at the most.

 

[sailcapt340]

I have a Speed Seal on my raw water impeller housing. What it does is replace the screw in backing plate with 4 large knurled head screws, a new backing plate with an O Ring gasket.
Now I’m not sure if there is a model for your engine but it’s worth looking into. I believe I purchased mine from a company called TOAD Marine years ago and it has served me well. It all depends on the type of impeller housing you have, but it’s a start.
In an emergency, it allows you to loosen the screws, slide the plate off, remove and install a new impeller. That sounds easy, but in a real life application, I’ve never had to do it. And I’m not complaining about that, but it does make yearly or biyearly replacement much easier and would eliminate the gasket.
it’s something to think about.

 

[dlochner]

I have a Speed Seal on my raw water impeller housing. What it does is replace the screw in backing plate with 4 large knurled head screws, a new backing plate with an O Ring gasket.
Now I’m not sure if there is a model for your engine but it’s worth looking into. I believe I purchased mine from a company called TOAD Marine years ago and it has served me well. It all depends on the type of impeller housing you have, but it’s a start.
In an emergency, it allows you to loosen the screws, slide the plate off, remove and install a new impeller. That sounds easy, but in a real life application, I’ve never had to do it. And I’m not complaining about that, but it does make yearly or biyearly replacement much easier and would eliminate the gasket.
it’s something to think about.

Alas, Speedseal is no more, unless some enterprising person bought the business. It was a good product, I had one on my last boat.

 

[sailcapt340]

To quote Johnny Carson….”I did not know that“! What a shame that is. Well it will give you an idea of how well it performed over the years. Simple design, works like a charm, makes you wonder why it would just go away.
I’m sorry Lee, I tried.

 

[dlochner]

To quote Johnny Carson….”I did not know that“! What a shame that is. Well it will give you an idea of how well it performed over the years. Simple design, works like a charm, makes you wonder why it would just go away.
I’m sorry Lee, I tried.

If I remember correctly, he was an older guy who ran into some health issues. He advertised the business on his site for a while, but apparently no takers.

 

[Terry Cox]

Hi Lee, we purchased Belle-Vie, a 1991 P42, in 2002 when it had 650 hours on the engine, a 4JH2-TE. It appeared that the sea water pump cover had never been removed, so probably original impeller. The PO had a spare that came with the boat. Over the years we put about 1,400 more hours on the engine with no indication of a problem. Then a couple of years ago or so we had some issues with the sea water impeller on our Genset, but eventually were able to resolve them.

Last year, out of concern over the Genset issues, I decided it was time to check out the main engine impeller thinking that by this time it would have cracks in the vanes or perhaps a missing vane and in need of replacement. Well, what a surprise when I pulled the original impeller out only to find it looked brand new. No cracks and no sign of vane fatigue. To be on the safe side I did replace it with the spare, but decided to keep the old one as a spare.

Just another point of reference on whether your impeller needs to be checked, replaced, or not; your call.

 

[sailcrazy1]

We have a Yanmar 4JH-TE, and the raw water pump is on the opposite side of our eng access.....we usually need to remove the alternator, the whole pump assembly, and then take the cover plate off-a real difficult spot to get to. We average around 100 eng hours/season, and we change the impeller about every 2nd-3rd year-but have gone as long as 5 years. Every time we do the change, the old impeller looks like new with no visible cracks or lost blades. We do carry a couple of spares, but after 20+ years on this boat have never had to use them mid-season. But....our Onan genset-now that's a different story. We've gone looking for broken blades mid season, or after only 1 season, more than a couple of times. Who knows when, but I'd guess in your situation every 2-3 years-or even every 4 years- is a reasonable plan.

 

[dlochner]

In January 2020 we purchased a Honda 5hp OB for our dinghy. Due to changes in plans from Covid, we did not place the OB in service until June 2021. By then the impeller had taken a set and was causing some overheating. Honda told us we should have replaced the impeller after 1 year, even though the OB sat in my garage for the first year. In 38 years of boating with a half dozen small outboards and a couple of diesels, this was the first time I had an impeller fail, and it failed before I even used it.

 

[SEMPERAVANTI41]

Sailcrazy1, you may want to relocate your water pump as per Art Boas post. I have done it and now the water pump is on the face of the crankshaft pulley. Turned a 2 hour job changing the impeller into a 10 minute job.
As far as the gasket, I have used Permetex self forming gasket from a tube with good results.

 

[dlochner]

Sailcrazy1, you may want to relocate your water pump as per Art Boas post. I have done it and now the water pump is on the face of the crankshaft pulley. Turned a 2 hour job changing the impeller into a 10 minute job.
As far as the gasket, I have used Permetex self forming gasket from a tube with good results.

Do you have a link to that post? The 3JH2E water pump access between the pump facing aft and the starter. In theory there is sufficient room to remove the impeller, in practice not so much. Would love to turn it around.

 

[Ralph Johnstone]

We average around 100 eng hours/season, and we change the impeller about every 2nd-3rd year-but have gone as long as 5 years.

We have a different raw water pump on a Yanmar 2GM20F but find the same performance with about 100 hrs/yr. After the first 10 years of dutifully checking the impellor every year and seeing no wear, I decided to change the impellor because it was getting old, in perfect condiiton but still getting old. So I installed a new impellor and kept the old one as a spare. 13 years later the new one is still in perfect condition but I only check it every 3-4 years.

So that's two impellors in 23 years. I always get a kick out of the posters on here who religiously change their impellor every year or two.