I HAVE A 1981 4HP. MERCURY MODEL 1040RSERIAL#5805487 NO WATER FLOW WHEN RUNNING, OR WITH EARMUFFS ! NO WATER OUT OF FLUSHING SCREWHOLE WITH EARMUFFS, EITHER.IS IT THE IMPELLER, OR BLOCKED? ANY ONLINE MANUALS OR DISMANTLING INSTRUCTIONS, OR SCHEMATICS? THANKS FOR THE EXCELLENT HELP, to PAUL M. He put me on the right path!
Welcome to Iboats, DOMBUM!2 cylinder 4hp right?If water isn't getting up to the flushing screwhole, its either blocked at the impeller, or it's blocked at the grommet at the top of the water tube, just under the engine. Detach the lower unit and attach a garden hose to the water tube. Then try to send water through the engine.While you have the lower unit apart, replace the impeller.Good luck! Drawings online.For JB: Evening!