on my 1966 40hp rude water comes out the pee hole on the back of the motor fine at a idle and a around 10 mph once i go wot water is not coming out that i can see of really comes out at idle though
Part of the problem may also be t-stat related. Possible it's not coming all the way open or is stuck partially open. Do as suggested in the previous posts and also replace the t-stat.