SUZUKI WATER PUMP CASE: RESIN INSTEAD OF STAINLESS STEEL

[HANDRIC]

Dear All,

For your benefit, I’m pleased to call your attention to the following:

Suzuki outboard motors DF 90 and DF 115, year 2006, with engine no. starting respectively in 680686 and 681518 are equipped with a Resin Water Pump Case, instead of a Stainless Steel Water Pump Case.

(According to SUZUKI publicity, when I bought my DF 90 I thought that it had a Stainless Steel Water Pump!)

In order to prevent the onset of the Resin Water Pump Case fusing by the friction of the Impeller against the resin surface in case of lack of cooling water, SUZUKI inserted a Metallic Sleeve between the Impeller and the Resin Water Pump Case.

Furthermore, in between the external surface of the Metallic Sleeve and the inner surface of the Resin Case they provided for an air interface, to reduce heat transmission from the Metallic Sleeve to the Resin Case.

In order to prevent the infiltration of water into the air interface between the resin Water Pump Case, SUZUKI invented a system of sealing: one Annular Sealing No. 1 at the top of the Metallic Sleeve, and one Annular Sealing No. 2 at the bottom of the Metallic Sleeve.

A pump case made of stainless steel or other metal suffers only from two drawbacks: is heavier than that made of resin and is more expensive to produce.

The resin pump case is lighter than that made of stainless steel or other metal and the cost is low because the materials are inexpensive and the processing cost is low.

Of course these are the reasons from the manufacturer point of view to change from stainless steel case to the resin case.

From my point of view, as a user I would prefer to pay more to have an engine with a stainless steel water pump case, and have as unique concern to replace the impeller when necessary, rather than to have other sources of potential problems: the resin case, the metallic sleeve, the annular sealings …

Now is up to you to make your own evaluation! Don’t hesitate to contact me if you wish.

Kind regards

 

[rodbolt]

Re: SUZUKI WATER PUMP CASE: RESIN INSTEAD OF STAINLESS STEEL

nylon housings with stainless inserts have been on most outboards for 30 years or so, while they dont tolerate dry running they have several advantages over a solid stainless housing. the biggest is the fact that by reploacing the wear plate and insert the pump can be easily and cheaply rebuilt. the solid housing,once the wear surfaces are worn, has to be replaced. mercury went to a solid housing some years back on its V6 and some sterndrives. however rather than being a casting its a stamped and welded model. works well.
the outboard pump is a dual type pump, at low speeds its a positive displacement and at higher speeds its a centrifigal type pump. either way the seal between the top and bottom of the impeller is critical. if the surfaces wear the pump loses effciency rapidly.
the only advantage I see with an all metal housing is about 60 seconds more tolerance of dry running before the pump is toasted.

 

[HANDRIC]

Re: SUZUKI WATER PUMP CASE: RESIN INSTEAD OF STAINLESS STEEL

Thank you, Rodbolt, for you so technical and comprehensive information and mostly for your so kind support. I’m a little bit more comforted now!

Many thanks again.

nylon housings with stainless inserts have been on most outboards for 30 years or so, while they dont tolerate dry running they have several advantages over a solid stainless housing. the biggest is the fact that by reploacing the wear plate and insert the pump can be easily and cheaply rebuilt. the solid housing,once the wear surfaces are worn, has to be replaced. mercury went to a solid housing some years back on its V6 and some sterndrives. however rather than being a casting its a stamped and welded model. works well.
the outboard pump is a dual type pump, at low speeds its a positive displacement and at higher speeds its a centrifigal type pump. either way the seal between the top and bottom of the impeller is critical. if the surfaces wear the pump loses effciency rapidly.
the only advantage I see with an all metal housing is about 60 seconds more tolerance of dry running before the pump is toasted.