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Water intake.

Posted: Fri Mar 22, 2019 11:06 pm
by Hugz
I was reading on another seagull forum about the difference of the water cooling system operating when the motor is moving through the water. The point was made that the water pressure from forward movement pushed water into the slots increasing the volume of water passing through the motor. A simple concept yet l don't recall it being mentioned on here. Has merit.

Re: Water intake.

Posted: Sun Mar 24, 2019 1:21 am
by Oyster 49
Well forced induction of cooling water is a something seen on other outboards for sure.
I’m not sure if movement of the boat through the water makes a difference or not, I suspect it’s not measurable.

Re: Water intake.

Posted: Sun Mar 24, 2019 9:29 am
by Charles uk
I assisted in the comparison tests on the new style QB water pump impeller for BS, a new style & a new old style were compared in a Kingfisher on the freshwater Thames.

Pump flow was measured at various revs mobile & stationary, the performance of both impellers was close to identical & my recollection of the stationary figures was almost no difference.

But on the other hand I have several 60's class B racers that never had water pumps, Konig, Carniti & Anzani's.

But you also have to ask yourself which would be better hotter or colder?

Re: Water intake.

Posted: Sun Mar 24, 2019 1:32 pm
by Rob Ripley
I would imagine it be more due to the centrifugal nature of the impeller forcing water to the engine more than water pressure on the inlets. Perhaps if the inlets were smoother (or larger) it might make some difference. On the other hand how hot does the exhausted water get ?

Re: Water intake.

Posted: Sun Mar 24, 2019 4:32 pm
by Gannet
It is worth noting that with gearbox used on the LS initially had 2 water inlet holes. This was changed to 3 holes later - possibly sometime around 1953 or it might have been 1954. Presumably BS thought it was advantageous to make this change. Although the change might have been made to reduce the chance of some seaweed, or a leaf for example blocking the water inlet, rather than to just to improve the cooling water flow rate.

I know from experience with FVs with their similar 2 water inlet holes on the smaller 10:21 gearbox, debris in the form of seaweed and leaves does sometimes completely cut off the water flow. It seems possible that 3 holes would be just a little bit less prone to this problem.
Later on the smaller gearbox had two big slots in lieu of holes. Was the bigger gearbox changed in a similar way?

Apart from blockage, I would have thought that the cooling water flow rate was well adequate, except of course at tick over speeds, to which 2 or 3 holes or slots would not have made any difference.


Re: Water intake.

Posted: Sun Mar 24, 2019 10:09 pm
by cookie1
Interesting comments . The Seagull cooling system much more forgiving than the rubber impeller set up but not used by any modern motors . For reliability reasons I use modern outboards as I'm a commercial fisherman but I still think there is a market for a basic no nonsense motor !