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The difference with the 250/275V and the newer model Capilano Helm pumps, is that the new Capilano Pumps have a built in check valve, whereas on the older systems there would have been a Model 50 uniflow valve. If you are replacing an old system with a new one, the uniflow valve will not be needed in the system, simply remove the third line going to the valve and use only the two port and starboard lines directly back to the steering cylinder.
It is impossible to lick your elbow.
At least 75% of people who read this will try to lick their elbow!