2008 115 Optimax Serial # 1b723350

About 30 days ago I hit a sandbar and sucked up a bunch of compacted sand and shell that clogged my cooling system. I eventually got some telltale stream going but not good flow and started getting overheat alarms*. I limped back to the ramp. Changed water pump and gasket(oem parts always), was due for it anyways. Better flow but still not right and still getting overheat buzzer. Replaced the strainer in the motor.. Pretty good flow after that. Idled for 20+ minutes with no alarms...thought I was good, but as soon as put in on plane I get the alarm within 10 seconds or so. The telltale looks good and the water doesn't feel hot even when the alarm is going off.

There is a check valve in the water flush hose between the hose hook up and powerhead. The shell had this clogged to where it would only piss on the earmuffs. I eventually got the check valve to open up but today I noticed that when the engine is running in the water there is a small amount of water leaking out of the hose attachment. If that check valve was working properly it seems there shouldn't be any amount of water coming that way. It seems it would be a very small reduction in water pressure/flow but maybe that's all it takes. Any chance that check valve is the issue? I don't know what else to try?

*I don't have smartcraft or water pressure gauge, just audible alarm. The alarm I getting is the solid beep, and the motor reduces RPM to "guardian" speed.

Thank you for input advice in advance!