Well, after scratching my head all summer and picking the collective brains of all here, I may have found the cause of my weird temp fluctuation problem. This is a Merc 888, Ford 302, with Osco log style manifolds. The symptoms were that the temp would stay at a constant 140 at idle and would hover around 160 if I kept the throttle under 3000 or so. Anything more,a nd the temp was all over the place between 140 and 180, mostly on the 180 end. At idle, you could feel air bubbles in the hose exiting the manifolds.<br /><br />As a note: before this all started, the temp never got above 160, hovered around 140, even at WOT and would cool back off quickly, took forever this summer. <br /><br />The Osco manifolds have 4 drain plugs each. While winterizing last year, I installed a petcock in the 2nd hole of each to let me drain the water easily this year in case I didn't get fully winterized before a cold snap. I pulled the plugs and the petcocksout this afternoon. water came out of the front holes and trocled out the holes the drain valves were in. After prodding a bit with a piece of copper wire in the back 2 holes on each side, and the holes the valves were in, water came flooding out the all holes. <br /><br />Are the passages in manifolds so small that the small bit of the valves that protruded into the cavity was blocking flow? I'll put regular plugs back in during the spring comissioning, but is there any reasonable way to check for further junk in the manifolds without removing the end caps?
