I have a 2005 Merc. 50 HP, 2 cycle ELPTO. Last weekend notice the water pump indicator hole had maybe a 1/3 of the flow it should have coming out of it. Because of its age and relatively limited hours, I'm hoping its not an impeller change needed. This morning, checked the primary & secondary intakes, looks clear. No fishing line around prop (seal area appears normal). I hooked up the water hose to the intakes, cranked it in the driveway, still very slow flow out if indicator. Besides dropping lower unit, is there some trouble shooting ideas out there? Blockage somewhere thats a fairly quick check? I put myself through college working in an automotive machine shop so turning wrenches or having tools is not an issue. Just have not worked on many outboards, at least not enough to know all the tricks/trouble shooting. Naturally, I'd like to avoid tearing it down if possible.