I need some sage advice from the experts. My 1970 60 HP 3 cylinder Evinrude (model 60073D) began misbehaving. It would start, idle and accelerate fine but after ~ 2 minutes at WOT would gradually loose power and shutdown. The motor would crank with spark and the head was ?Warm? to touch. Ball was hard & tank vented. No Over-temp warning and circuit/light checked OK. No ?pisser? on this engine. After about an hour the motor would restart & run but time to lose power was shorter. Toggling the choke extended run time. Rebuilt carbs and cleaned main jets / all passages but problem repeated. Extracted 3 gallons remaining in 6 gallon fuel tank and let it sit overnight in a clear container. Mixture stratified into 2/3 gas and 1/3 water. Drained carbs, fresh gas, changed fuel pump (checked for diaphragm leakage into crank case) and problem still occurred.
Checked compression: 105 to 115 psi on all 3 cylinders. Pulled exhaust covers (never been off in 41 years) to look into ports. Found carbon as expected. Some scoring on pistons and rings (can barely feel with finger nail) and cylinders look OK. I do realize that there may be deposits on the walls. Have pictures to upload if I can compress them. On a hunch that water was getting into the cylinders I pulled the head. No evidence there except lowest cylinder looked cleaner than others. Head water jacket is next on my list. The gasket at the base was in bad shape. Is it possible that the water pump may have been injecting water into the cylinder? The parts are all original except for head gasket replaced 7 years ago. No cracks apparent anywhere.
With the power head off I plan to disassemble for a closer look at the pistons, rings & cylinders & "Mic" the parts. I have new gaskets, a new impeller, seals and grommets along with a ?pisser? constructed from IBoats thread.
Before I invest in having the cylinders honed (or bored as necessary) am I missing something that would cause this problem to re-occur? Is there a machine shop near Boston that would be capable of working the cylinders? If cylinders clean up within standard spec (3 inch bore per factory manual) would new rings on original pistons compromise the rebuild? Having a problem finding Pistons for this motor; Wiseco is No Joy & waiting on Sierra.
Sorry for the long winded description and thanks for any suggestions.
B53
Checked compression: 105 to 115 psi on all 3 cylinders. Pulled exhaust covers (never been off in 41 years) to look into ports. Found carbon as expected. Some scoring on pistons and rings (can barely feel with finger nail) and cylinders look OK. I do realize that there may be deposits on the walls. Have pictures to upload if I can compress them. On a hunch that water was getting into the cylinders I pulled the head. No evidence there except lowest cylinder looked cleaner than others. Head water jacket is next on my list. The gasket at the base was in bad shape. Is it possible that the water pump may have been injecting water into the cylinder? The parts are all original except for head gasket replaced 7 years ago. No cracks apparent anywhere.
With the power head off I plan to disassemble for a closer look at the pistons, rings & cylinders & "Mic" the parts. I have new gaskets, a new impeller, seals and grommets along with a ?pisser? constructed from IBoats thread.
Before I invest in having the cylinders honed (or bored as necessary) am I missing something that would cause this problem to re-occur? Is there a machine shop near Boston that would be capable of working the cylinders? If cylinders clean up within standard spec (3 inch bore per factory manual) would new rings on original pistons compromise the rebuild? Having a problem finding Pistons for this motor; Wiseco is No Joy & waiting on Sierra.
Sorry for the long winded description and thanks for any suggestions.
B53