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Speed Seal Installation

Written by Tim Lackey of
Used by permission of author

Note: The author was working on a 3mg30-yeu engine.

You can purchase a Speed Seal for many engines from Torresen Marine’s online ships store at

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.


Water Pump Location

Note: Yanmar has addressed this issue on their new 3YM30 engine. The sea water pump, oil dip stick, oil and fuel filer will all be on the front side for easy access and maintainence.

For this reason 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.

Although made in England, Speed Seals are available from Torresen Marine in the USA. When ordering Speed Seal’s you need to know which Yanmar you have. If you have a 2gm20(F) or 3gm30(F) you need to determine if it is a ‘YEU’ engine. If you engine is post 1997 or if it’s serial # begins with E then you have a YEU engine with a different water pump and will need a different Speed Seal.
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. .

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 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”. Note: impeller removal is not part of standard winterizing at Torresen Marine but available at request.

While I have the pump off, I will be installing a brand new impeller. 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).

We stock Speed Seals for many Yanmar engines so delivery can be as fast as you desire. 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.


Speed Seal Parts

Final installation calls for some waterproof grease on the threads and gasket. For demonstration purposes, I reassembled the pump without the grease.


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.

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.


Removing the Speed Seal

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This entry was posted on Monday, December 29th, 2003 at 9:29 am and is filed under Main Stories. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

One Response to “Speed Seal Installation”

  1. Robert Cross Says:

    I have had a Speed Seal for a number of years on my 1988 vintage Perkins 4X236 diesel propulsion engine. I would like to purchase 2 O rings and 2 new thumb screws. Thank you, Robert Cross

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