Yanmar Impeller Replacement

[sailfree20770]

This is for the Hunter 376 with 3jh2e engine, though I'm sure other boats will be similar.

First, thanks to all the previous posters on the topic! It was a big help to read what others had done. I see the original thread is closed, so added a new one.

The info on getting the right angle pliers to remove the impeller is right on. Can't imagine another tool that would work. There may be a "puller" made for the task, but on this engine the space between starter and pump is so small, it's doubtful it would fit. Found these pliers worked fine:
http://www.harborfreight.com/11-inch-90-angle-long-reach-pliers-39539.html

Previously, some removed the alternator, while others cut an access hatch through the head compartment. After considering the situation for some time, decided the hatch was really mandatory. The starter, solenoid, water pump, engine mounts, and several wiring connections are now easily accessible. The hatch is 15" wide by 18" high, made to match near the aft and lower edges of the engine cover.

It was a bit time consuming to cut and trim the hatch, but just didn't feel comfortable knowing all that stuff was so hard to get to.

When replacing the impeller, be sure all the blades are going the right direction. The manual says to give it twist while installing, but it's not easy. Had to do it three times to get it right. Some posts say the blades will be OK no matter how they they are installed initially, as the first time the engine starts they'll self align. Not so. I found the previously installed impeller had one blade still bent backwards. While that probably only reduced the output slightly, I have to believe it would shorten the life of the impeller.

Later on... I read to use an electrical tie wrap to keep all the blades in the right position. That's a good idea!... will use next time.

 

[bigbrownpilot]

Thanks for the info, sailfree. We have a 2002 Hunter 380, and I have purchased an access hatch and plan on cutting a hole to access the impeller as soon as I have time to do the project. I replaced the impeller on my H306 before we sold the boat, and you are correct about the difficulty in getting all the blades to line up correctly. Good tip to use a small cable tie to hold them in the correct direction until it is seated in the pump housing!

Dave

 

[rfrye1]

I own an H376 and have done the hatch thru the head conversion. Does make it easier. Every time I change the impeller, I still curse the engineers at both Hunter and Yanmar for this design flaw. I also use the "speed plate?" Which replaces the impeller cover plate and be tightened by hand. FWIW, I change my impeller once a year, sitting at my dock with a cold beer. I figure it's easier to do a little preventative maintenance on MY terms than in the seaway when it's not on my terms.

Bob

 

[bigbrownpilot]

I like the concept of the speed plate, but do you think it is worth it? I just bought a thumb drive that I can put a socket on. Looked like it would work just as well, but I haven't changed mine yet.

 

[Don Lucas]

I think some people change their impellers for sport! This yearly replacement stuff is just a waste of time, check your manual!

 

[Scott B]

I think some people change their impellers for sport! This yearly replacement stuff is just a waste of time, check your manual!

I RTFM, it says..... every 250 hours or one year, whichever comes first....

 

[Don Lucas]

I RTFM, it says..... every 250 hours or one year, whichever comes first....

Mine says 6 years, 800 hours!

 

[Scott B]

Mine says 6 years, 800 hours!

Seems to me we've had this conversation before???

 

[Don Lucas]

Seems to me we've had this conversation before???

I don't remember it. The replace impeller every year people always make it sound like a super critical thing needing to be done each year or your engine will be destroyed, even though just as many will report that they have never replaced theirs and everything is fine. But it doesn't matter really to me what others want to on their boats.

 

[Scott B]

I don't remember it. The replace impeller every year people always make it sound like a super critical thing needing to be done each year or your engine will be destroyed, even though just as many will report that they have never replaced theirs and everything is fine. But it doesn't matter really to me what others want to on their boats.

It would be interesting to find out why Yanmar would have shortened the replacement time period so much in the 4 years between your boat and mine.

 

[artboas]

Nothing is worse than the 4JH yanmar

It would be interesting to find out why Yanmar would have shortened the replacement time period so much in the 4 years between your boat and mine.

I have a 49 with the 4JH
The impeller is on the back of the engine, and the engine is mounted sub floor.
To replace the impeller you need to either remove the alternator , the intercooler, or both.
Reminds me of the old British crap cars that you needed to pull the engine to replace spark plugs.
Yanmar should be shot for making an impeller replacement a 2 hour ordeal in perfectly calm water. In rough seas, you'd be safer getting the boat towed to port.
And this ain't hunter's fault. It's clearly a bonehead design from Yanmar.
FYI, I worked on designing a tool which could get access to pull the impeller. No way. And a Speedseal cover won't help you. There is just no access: plain & simple.
So, I got really freaked about a water intake blockage, as I didn't want to lose the impleller. To lower my risk, I installed an Aqualarm water intake sensor, which monitors water flow on the raw water into the strainer.
I then put an automatic shut down, which kills the engine if the intake pulls in a bag, or something. Of course I put in a shutdown bypass switch which just sounds a loud alarm instead of killing the engine.
It works amazingly well.

 

[Don S/V ILLusion]

Yanmar should be shot for making an impeller replacement a 2 hour ordeal in perfectly calm water. In rough seas, you'd be safer getting the boat towed to port.
And this ain't hunter's fault. It's clearly a bonehead design from Yanmar.

Let's not misplace blame completely here.

I have a 4JH on our boat and had the same engine on our previous boat (a Hunter 40.5). In both cases, it was a simple and easily accessible task to access and change the impeller.

It's a function of how the boat manufacturer chooses to place the engine, not Yanmar, who creates the problem.

 

[Scott B]

I guess I'm spoiled? or Hunter figured it out. I pull the stairs and impeller is front and easy to change. Oil filter has an easy access hatch starboard, and water seperator and transmission through aft cabin hatch.

 

[Steve Dion]

I was told by a Yanmar dealer that the impellers on the JH models lasted a lot longer than they did on the GM models.

I don't know if this is fact or perception on her part.

I do know that if you don't have an access port on the port side of the JH engine it is a S.O.B. to change. The new Yanmar impellers also have threads so you can use their new "magic" tool to extract the old ones.

 

[Akapeterc]

I have a 4JH3E in my 44DS. When my motor was due for a service after I'm 150 hours (only 9 months) I took a spare Johnson impeller that I had on board along to the yanmar dealer who told me that they wouldn't recommend using any thing except a yanmar impeller. So she opened up the sealed Yanmar box to find a Johnson impeller inside the box. She said she couldn't sell me one of them as it was the same as the one I had in my hand. When I pulled the old one out it only had three teeth left on it

 

[Akapeterc]

My manual says 250 hours I think but clearly mine didn't last 150 hours. The mechanic who changed it with me got all the fins out of the heat exchange. Even with only 3 blades I never had a heating problem. I nearly didn't change it but after seeing it I will be doing mine every year. I also did replace the cover plate as it did have a fair amount of where in it.

 

[bananabender56]

Has anyone used the silicone rubber impellers made by Globe?

 

[Don S/V ILLusion]

Has anyone used the silicone rubber impellers made by Globe?

I have no first-hand knowledge but, for what it's worth, I was told by a good marine diesel mechanic whom I trust that they have a reputation for failing at the spindle, I.e., the spindle and vane body separate such that the spindle turns but the blades do not.

Maybe someone else knows if true.

 

[bananabender56]

I have ordered a couple as spares but have yet to try

 

[artboas]

The 40.5 & 49 are totally different

I have ordered a couple as spares but have yet to try

I used to own a 40.5. Changing the impeller was simple. Front access. Easy stuff.
On the 4JH model on the 49, the water pump faces the rear of the engine, and us underneath the alternator. If your engine was mounted up high, and you had full access to the rear of the engine, it would still be a pig of a job because the alternator still obstructs it. It would be doable, but still not great.
On the 49 / 50, the engine is sub floor.
You can't even see the water pump, let alone work on it.
Here are the only solutions I've heard from 49 / 50 owners:
Remove the alternator
Remove the water pump
Remove the inter-cooler.
There is no way to cut an access hatch, as there is nothing to access.
To repeat, it is below floor, underneath the inter-cooler & alternator.
The worst design error yanmar has ever done