TOPIC: 1965 Merc 500 quick help

The boat runs fine, I replaced the water pump last year but the tell barely dribbles water, it never seems to overheat but more water comes out of this bolt (horizontal) then the tell, is there a seal in there that is leaking?

What's coming out around the bolt is exhaust water. there is a seal there but to replace it you"ll need to pull the powerhead. I have seen people use silicone around that just to eliminate the mess. As for the telltail the hole is probably plugged try pushing a wire up through it & maybe blow air up through.
Tim

this looks to be a 1964 25th anniversary Merc 500. There should not be a water tube under the cowl for the tell tail it will shoot out the bottom of the block cowl so you should not have to worry about a kink in a hose. You probably have a little mud-dobber up there but as like Tim instructed take a small wire and try to clean it out she should start to pee out the hole for you.
Any leak in the system will through the pressure off and will weaken the tell tail flow. When you replaced the impeller did you look at the cup it rides in? Was it scored? If so you do not want a worn or scored cup or wear plate.
Re trace your steps. Take your time be sure everything lines up. if you have a compressor clear out any holes. if you can it would be a good idea to replace the seals around the top motor mounts.
Good Luck

Why the idea of the tell being plugged never occurred to me is beyond stupid, it was plugged, thanks guys.