............. both pumps that i have tried have signs of ware on inside of cover plate, do you think that these pumps are just tired through age?
also if i cover up water inlet and weep hole on leg can i flush water back through leg to check the pivot tube for leaks without doing any damage? both of these pumps pull water from a bucket on the deck next to engine easily, do you think that this is helped by syphonic action as outlet is lower than inlet, as apposed to the opposite when hose is connected to leg? as a last resort is there an inline pump that i can fit between leg and current water pump?
Wear at the cover plate can be corrected to some degree (dressing it by machining, etc.), but this often indicates that the same or similar degree of wear has occured at the oposite "thrust surface" of the pump body. There is no correct "fix" for this, other than replacing the entire pump. All surfaces must be near pristine. The impeller must also be in near pristine condition.
How is the cover gasket?
Have you checked the pump body impeller "cam"?
If the cam is worn in a way that breaches impeller blade "wiping" and/or "compression" action, it will not create enough suction to pull sea water in.
(this image does not actually show a separate "cam"..... the next image does!)
Flushing water back through the drive will create a pressure scenario. Pressure is not a good means of simulating or locating a "suction" leak..... these are two entirely different principles. If you want to locate a suction leak, then use suction, and a foam that will disappear at the leak. Some use shaving cream.
As per your "last resort" suggestion: No need to re-invent the wheel on this one. Replace the suspect components with "like" OEM components. These systems work very well when they are in correct working order. No need to substitute or circumvent what the OEM has done. Trust me on this one!
Suspect areas:
Water Neck fitting as per suggested earlier.
Lower pivot tube O-ring seal.
All sucessive hoses and hose clamps.
Copper suction tube from transom shield water tube/hose to engine pump (if so equipped).
Rubber seals directly at pump connection (very important that these be NEW).
Pump Impeller thrust surfaces (cover and deepest surface within the pump bore)
Impeller itself..... (must be correct for the pump body, and in near pristine condition)
The sea water cooling system is the "heart" of the system that keeps engine operating temperatures within a safe range. All too often we look for short cuts, or anything that is a "quick fix", rather than a more difficult and more time consuming
correct fix.
Most anything, and most any cost in doing so, will be paled by comparison to that of an engine replacement..... should you allow it to severely over-heat.
As for replacing the water neck fitting, I can't emphasize enough as to the importance of this!
I find it to be much easier to remove the transmission for water neck fitting access. Not all that difficult to do, and the access is greatly improved. This gives us oportunity to check several other items as well.
Transmission removal requires four new O-rings (drain plug, dip stick, oil drain-back tube, large bearing)
Heat the suspension fork in the area of the two water neck fitting fasteners prior to removing them! Keep the words "corrosion" and "snapped fastener" in mind.
Do these checks and items, and I'll bet your issue will be resolved.
