My 18 has an '88 Volvo SP-A drive (stroked sbc - raw water cooled - freshwater use ONLY) which has been absolutely bullet-proof, but I have run into a situation I cannot figure out. Hoping one of the Volvo gurus here on the board can help. The other day, we spent the afternoon anchored and relaxing. The drive was down in the sand - but the motor was not running. Left there and ran the 8 miles down to the other end of the lake and crossed slowly through a weed-infested area before powering back up and running back towards my home dock at about 3200 rpm. About a half-mile before I got to the dock i noticed the engine note got a bit louder through the open exhaust. I just assumed that the wind was blowing a bit harder in the direction I was running and thought no more about it as I had my hands a little full avoiding some idiot letting his 10 year-old drive his Sea Ray and a bass fisherman blocking the entrance to my lift. Anyway, as I pulled onto the lift, I smelled a bit of a burning rubber smell, glanced at my gauges and saw the temp was pegged. I shut it down and got lots of steam. Crap.
I immediately assumed that I had somehow clogged the intakes - either with sand or with weeds, and burned up the impeller. So, ran to the local marine store, got another impeller and changed it out. The old impeller was chewed up a bit - but not completely gone. Started up and still not pumping water. I pulled the hose off the pressure side of the raw water pump. Started up again. No water. Pulled the boat up out of the water and put the muffs on the lower unit (and of course, the blocking peg in the bottom of the leg.) Started it again. Still no water. Pulled the suction side hose off the raw water pump and turned on the water pressure to the muffs. STILL no water. Maneuvered the suction hose to where I could blow through it and everything seems clear. Put the garden hose into the suction side hose and the water comes right out through the lower unit.
I have had this lower unit off at least 4 times since I have owned the boat and all hoses are less than 3 seasons old. Any suggestions on why water won't come through the drive with the muffs on, but water will flow BACK through the drive (there isn't some sort of "one-way" anti-syphon valve on this drive, is there?) Hoping like hell that once I get THAT issue figured out and cooling water flowing back through the motor, that I haven't warped my aluminum heads...
Thanks for any and all suggestions.
ERIC