Mariner 30A Cooling Issue
I've had chronic cooling issues with my 1982 30A. A couple clearly my stupidity, the remainder mystifying. Anyways, latest incident as follows:
Went out Friday a.m., launched and tied up at the pier with motor idling and wife in boat while I parked truck. When I got back to the boat (maybe 5 minutes tops) very annoyed wife sitting there with my home-brew overheat alarm going off, motor stopped and temperature gauge above the 220 degree mark.
Thinking it would be best to get some cooling water flow going, after a short wait, I started up and pulled out at about 1500 rpm. Good flow from tell-tale and temperature dropped down to upper end of normal operating range. However, it never did get down to what I'd normally expect going only 1500 rpm (the gauge was showing what I'd normally expect at 2/3 throttle or above). Unfortunately I didn't have my fish finder installed so no ambient water temperature reading available. This was in San Diego's Mission Bay, near Sea World so I'd expect water temps in the mid-70's.
Thinking discretion as the better part of valor, I decided to abort and head for home. All the way in had good flow from tell-tale and stable (but high) engine head temperature.
At home, flushing through the muffs, I had good flow through tell-tale until thermostat opened. Then flow through tell-tale dropped down to mere dribble (with no change in water flow through muffs).
Pulled the thermostat and found some of the soft, white, mushy stuff that has showed up since I started using Salt Away. Squirted hose water through both ports in thermostat housing and in through tell-tale opening. A small bit of crud came out the exhaust port.(mainly some more of the white mushy stuff).
Today, fired up on the muffs again. Good stream from tell-tale till thermostat opened, then down to a dribble. Water coming out from exhaust port. Both dribble from tell-tale and water from exhaust port were hot, but not so hot I couldn't hold my hand there.
Impeller is exactly one year old. One year is about all I get from impellers before performance drops off markedly.
I'm going to replace the impeller today. Anything I should look for while the LU is off? I always squirt water through all accessible orifices when the LU is off.
Any reason why I seem to get only 1 year/impeller? Boat very lightly used. Am I buying crappy impellers or very old, on the shelf, stuff because of the age of my motor?
Any thoughts appreciated.