The Right Tool For The Job

I love the easy engine access our Hunter 376 provides. I really feel sorry for some of the folks whose blogs I read, when they post pictures of the cramped little holes they have to crawl into in order to service their engine. But there’s one routine task we have to perform that’s a real PITA, and that’s changing the raw water impeller. On our last boat, the raw water pump was a belt driven unit that was mounted right on the front of the engine and was totally easy to access.  But on Eagle Too, the raw water pump is gear driven and set into the engine block on the port side of the engine, tight up against the bulkhead. For reasons known only to a handful of Japanese engineers, the cover plate for the impeller faces aft, right in front of the starter. There isn’t enough room between the pump cover and the starter to use a socket wrench, and the location is almost impossible to get a visual on. You have to use a box wrench to remove the four bolts that hold the impeller cover on and pull the impeller entirely by feel. I actually can’t even get my hand into the space without first removing the alternator to open up an access. It just seems like a really bad design for something that has to be serviced pretty regularly. Some people actually cut a hole through the bulkhead and install a hatch in the head (bathroom) in order to have another way to approach this problem. We just didn’t want to cut a hole in the boat for a job that’s only done once a year.

Alternator removed to give me access to the area indicated.

This is the small space you have to work in. Raw water pump to the left, starter to the right.

One thing I did discover though is that having the right tool makes the job quite a bit easier. In this case, the right tool is a pair of right-angle pliers. The first time I tried changing the impeller, it stubbornly refused to come out. I had to use the old trick of prying at it with two screwdrivers to try and get it out of the pump body, ripping it to shreds in the process. One thing I did to make the next time go a little easier is that I coated the pump shaft with Tef-Gel before installing the new impeller. This Teflon based paste keeps parts from corroding and freezing together, and it’s very useful whenever you have to put something together that you hope to be able to easily disassemble again in the future.

The other trick was the pliers. Since there’s very little room to work, I thought the perfect solution would be to use a set of right-angle pliers to reach into the pump body, grasp the impeller, and then pull it out. A quick trip to Harbor Freight turned up exactly what I was looking for.

The owner’s manual for our Yanmar 3JH2E diesel engine says the impeller should be changed every 600 hours. After we returned from our last season of cruising, we were right at 650 hours, so it was due. While the job was still a bit of a pain, the combination of having used Tef-Gel when installing the impeller and using the special pliers to get into the tight space made the job go much easier.

It looks like the recommended maintenance interval was spot on, because when I examined the old impeller, I could see the beginnings of cracks on some of the vanes. Let this job go for too long, and these vanes start breaking off, travel through your cooling system and end up clogging the tubes in your heat exchanger, causing your engine to overheat.

Vanes just starting to crack.

If you’ve done this job, you know what a pain it is. Try the Tef-Gel and bent pliers. I think you’ll be pleased with how much easier things are.

If you haven’t done this job, what are you waiting for? Don’t let a worn our impeller leave you stranded.

7 thoughts on “The Right Tool For The Job

  1. Roger and Genie

    Hey Guys! We have the same engine and yes, it’s a pain to change the impeller. We, like you, remove the alternator but then take off the water pump too, which has it’s on complications. I was in Harbor Freight today but tomorrow I will be back to get the Tefgel and some right handed pliers! Thanks so much

    1. Robert Post author

      I’m not even sure how I’d remove the water pump! Hopefully we’ll never have to.I think you’ll find the pliers makes the job much easier though.

  2. Norm Kennard

    1997 376 Elysium from Annapolis MD here.

    Impeller changes are a complete PITA. This deck hatch is the same color as the head liner. Its on board and I’m going to cut it in over the winter. Won’t be that noticeable next to the engine cover as its a very narrow space. May paint it black or otherwise disguise it. Will let you know how it goes. I.P.S. Boat Deck Hatch 520-138 | 11 x 19 Dream White, GLS Stock #: 1061181-5H156, $59.95,

    If you’ve ever broke a cabinet hinge on the boat. This is the replacement for it. Hard to find. Blum Nickel Plated 95 Degree Boat European Style Hinge(PAIR), GLS Stock # 1018760-1#N4,

    Robert. Thanks for all of your contributions. I really enjoy your articles.

    Norm Kennard.

    1. Robert Post author

      Thanks Norm! I appreciate the links, and I’m glad you enjoy our posts. I’ve found that is also a great place to find pieces and parts for our boat. I hope the hatch install goes well for you. That mod was just a bit more than we wanted to do for a job that only gets done once every year or two.

  3. Gabriel Busuioc

    The other day I saw no water coming out of my cooling system. Changed the impeller, but the same…looked at several components but nothing. It turns out the exhaust/water mixing elbow was clogged… Aventura (1996 Hunter 376).


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