Re: 175hp 1977 johnson warning sing
That's good compression for that engine. It is not unusual for a lower unit to ingest sand/dirt into an engine-esp if it has been run in shallow waters and not trimmed for shallow water running. If dirt, debris has worked it's way all the way up to the thermostats, you may have ingested this same crud throughout the whole powerhead. First, I'd pull the covers off the head and inspect them for dirt. (Don't pull the whole head yet-just the cover.) If you find dirt in the head water passages, you may want to then pull both heads and check lfor crud in the water passages around each cylinder. Also check the 6 rubber water diverters in the block. They can deteriorate with age. If you have sucked up much of this debris/dirt, it came up through the water pump impeller in the lower unit. When dirt/sand comes in contact with the rubber impeller, it will quicly damage it and may gouge the stainless cup the impeller rides in. Drop the lower unit and check the water pump. Possible you need a whole impeller kit.
