I purchased a 1986 175 HP Evinrude VRO outboard this summer, it had good
compression in all cylinders and during my test run of the motor it ran
perfectly at low and high rpms. The test run was only for twenty minutes or
so. Since then I have been having power loss problems, specifically, after
running the motor at about 4500 rpm for about half hour or so the motor
suddenly bogs down, almost as if the gasoline supply has been cut off. If I
catch it bogging down and pull the throttle back it will still idle, and
then if I let it idle for five minutes or so, it will run at high RPM again
for another fifteen minutes before it does the same thing. I have checked
all the fuel lines, water fuel seperator filter, gasoline filter, and fuel
pump and they are all okay and functioning properly. The oil-gas mix I use
is 50:1, the VRO system was removed. I have tuned the motor and changed all
fluids. The power packs, the original owner tells me, were replaced last
summer. The motor is mounted on a 20' Grady White Overnighter. Does anyone
have any suggestions on what is causing this power loss, or diagnostic
procedures to follow to pinpoint the source? Russ H.