Raw Water Cooling Pump
This page was last updated on 21 March 2002.

Through a brilliant feat of design and engineering, the fine folks at Yanmar decided that it would be entirely inconvenient, difficult, and--basically--unsafe if they cleverly installed the raw water pump on the engine so that the face place faces backwards.  My hat is off to them.  At least the pump is located at the front of the engine where it can be reached, but sheesh...why did they decide to install it so that you can't service it without removing the whole pump?  May such marvels never cease.

Anyway, for this reason (although I would have installed one anyway, regardless of the pump orientation) I decided to install a Speed Seal safety cover on the raw water pump.  This is a truly clever design, intended to allow rapid removal of the face plate on the pump for inspection or emergency purposes.  From all I have read, these are well made and actually work as intended.  They feature a custom cover plate, fitted with an o-ring gasket, that is secured over the top of your existing pump with knurled thumbscrews--making it easy to remove.  Making it even easier is the fact that only a couple of the screws need be completely removed--the cover is slotted on one side, so that the opposite screws need only be loosened, and the plate can slide right off.  Ingenious.

I filled out the order form and faxed it to England, where Speed Seal is located.  Almost immediately, I received a phone call from a very pleasant chap (Alex Parker) who needed some more information about my particular water pump.  Apparently, the water pump design on the 2GM20F was recently changed, and he wanted to confirm which pump I had.  I didn't have the information he needed right at hand, so I went out to the boat to remove the pump and check.  I would have had to remove the pump to install the new Speed Seal anyway, so no time like the present.

Removing the pump (that's it behind the small pulley on the left in the photo) was easy, although it still would be a better design if you didn't have to unbolt it to check the impeller.  There are two bolts that hold the pump in place, one of which is installed through an adjustment bracket, used to tension the engine belt that drives the pump.  I removed the two bolts and pulled the pump out.  With the pump in hand, I was able to provide Alex with the pump model number so he could confirm which Speed Seal was the right one.  As it turned out, I have the new style pump (Johnson F4B-903  10 24509-01), which features its own O-ring on the inside instead of the standard paper gasket.  My service manual, purchased with the engine, does not show this, so it was an eye opener for me.  Apparently, Yanmar didn't see a need to rwpump.JPG (141047 bytes)ensure that the service manual was updated to reflect important changes to the engine.  I wonder what else is wrong.  Suffice it to say that I will be carefully checking all spare parts that I purchase for this engine now, actually confirming what the part currently on the engine is before ordering the supposed replacement part.  I imagine the standard impeller part number is incorrect for my pump as well.  That would have been a real bummer to find out in an emergency.  Anyway, my new Speed Seal is on its way from England as we speak.  Installation to follow.

When I removed the existing cover plate on the raw water pump for inspection (6 tiny screws), I found that the impeller, which had been in place all winter, would not spring back to shape when I removed it--the vanes that had been impellerinplace.JPG (146354 bytes) compressed at the top of the pump took a few days to regain their normal shape.  The practical problem behind this is that the pump would not likely have worked properly if I had used it this way--the vanes would not have sprung back against the bottom of the pump housing.  The lesson here is that your impeller should probably be removed for long-term storage to prevent this "vane memory".  While I have the pump off, I will be installing a brand new impeller (the Johnson model number for my impeller is 810).  The old one looked OK after a few days, so I'll keep it as a last-ditch spare (I will also have brand-new spares on board).

Exactly a week after I placed my order, the Speedseal came in the mail.  It's a nice looking piece of gear--simple though it is.  It's basically a machined brass plate that is designed to reproduce exactly the original face plate from a water pump, combined with knurled screws to fasten it.  The picture shows the inside of the Speedseal--the side that  the impeller will bear against.  I ordered extra screws along with it--it only needs four, but I figured it would be possible to lose one somewhere along the way, so it made sense to order spares.

Typically, the Speedseal comes with its own O-ring gasket, which is an additional improvement for most water pumps as it eliminates the need for an annoying paper gasket.  As mentioned above, however, my Johnson pump on the Yanmar already had an O-ring gasket, so the Speedseal is just a basic smooth plate designed to seal against the existing O-ring.

Final installation calls for some waterproof grease on the threads and gasket.  For demonstration purposes, I reassembled the pump without the grease for the moment.  I'm awaiting a delivery of some new impellers--might as well replace the one that's in there while the pump is apart (saving the "old" one as a spare) and will complete assembly and replace the pump on board once they arrive.  I sprung the extra dollar each for the Globe blue impellers that can run dry for 15 minutes without damage.  More details to follow at that point--along with a discussion on whether or not it will be feasible now (because of the Speedseal) to change the impeller without removing the pump from the engine.

I have to say I'm impressed so far--amazing how such a simple thing can be so precise.  The new Speedseal fits the pump beautifully, and seems to seal well.  The four knurled screws are very easy to turn, and easy to tighten properly--which had been a concern of mine.  But the diameter of the knobs is large enough to get a good grip on, and they crank right down.  I'm sure that the new cover plate will seal properly when water is introduced--something just feels right about the way the screws thread down.


removingspeedseal.JPG (161118 bytes)The cool thing is that two of the knobs fit into slotted holes, so removing the Speedseal for impeller access requires complete removal of only two screws--the other two stay in place after loosening them slightly.  This is a time saver.  There's a demonstration available on the Speedseal website.  I marked the direction of impeller rotation on the back of the cover to make it easier to install the impellers in the future; the original Johnson Pump cover plate also had this marking.

Glissando, Pearson  Triton #381

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