I was cruising with my 1976 Merccury 500 today. It fired up easily and ran like a champ at 3/4 throttle for about 10 minutes. Then suddenly the RPMs dropped to just above idle. (It was a very fast reduction in RPM, as if I had chopped the power.) I couldn't get it much above idle the rest of the day. If I applied power, it felt/sounded like the engine was loading up, but the RPM wouldn't increase.
Idled back to the ramp against an outgoing tide... long ride!
When I returned to the house, I took the plugs out. (They have perhaps 10 hours of use on them.) They were rather black and appeared to have specs of carbon on them. I replaced them with new ones and started it in the driveway - started right up. Going to put it back in the water for a test run next weekend... but before I do, I'm wondering what else I should check.
What can cause a sudden power loss like that?
Gas was brand new and ethanol free
carbs and fuel pumps cleaned and rebuilt last year
Maybe I misadjusted the carbs and it's been running rich ever since... and the plugs just "gave out" suddenly? Don't think it would work like that, though.
Thanks in advance.
Idled back to the ramp against an outgoing tide... long ride!
When I returned to the house, I took the plugs out. (They have perhaps 10 hours of use on them.) They were rather black and appeared to have specs of carbon on them. I replaced them with new ones and started it in the driveway - started right up. Going to put it back in the water for a test run next weekend... but before I do, I'm wondering what else I should check.
What can cause a sudden power loss like that?
Gas was brand new and ethanol free
carbs and fuel pumps cleaned and rebuilt last year
Maybe I misadjusted the carbs and it's been running rich ever since... and the plugs just "gave out" suddenly? Don't think it would work like that, though.
Thanks in advance.