I have a Motorola SURFBoard 6141 modem that is about 3 years old.  Lately, my connection has been dropping out around 3pm EST (+- an hour or so) and then works intermittently (10% of the time) for the rest of the night.  When I am connected, I get about 30 down and 6 up which is decent for cable service. 

I called Comcast and the tech told me that they no longer support that Modem and that I need to get a new one or "rent" theirs for $10/month.

I call BS and think that there is something wrong with their service.  The timing has me suspicious since kids are getting home from school and people are coming home from work so I thought that might be using up bandwidth.

My current setup has my modem about 3ft from the service entrance in my house (to minimize coax) with cat6 run to my wifi router on the first floor in the middleish of the house.

A tech is coming out in a few days and I purposely scheduled him to be here when it's likely to be down. I'm just looking for some input or troubleshooting suggestions. 

Did you ask the rep that you talked to at Comcast to check the signal levels on the modem? If he say he can't do that then ask for a manager. If their system is anything like the cable company I work for they can check the levels. Other than that could just be the modem going out. Make sure it has room around it as they tend to get hot.

Thanks.

I had a tech out here last week and he said the signal was high at -15dB which was out of spec.  He said it was supposed to be between 10 & -10dB.

I can check the SNR and power level from my browser.  They are currently at 39dB and 8dBmV and usually stay there, even when I lose connectivity.  Would that mean I have a problem inside my network, downstream of the modem?

The modem is in my garage, about 50 degF and isn't too warm to the touch.

I had issues with our cable modem, having a 100 mbps account I was seeing 5 mpbs and swing wildly up and down, similar to yours usually after school and on into the night. Had tech support check it, he reprovisioned the router to use a different channel is what he claimed, it seemed to do better but was getting buffering from time to time watching shows on Kodi with USNow TV. I ended up upping my service to 200 mpbs and it is super solid, getting 50 mpbs up and down solid. I know there is usually only so much room on a pipe, I recall a similar deal with DSL one time, the line I was on was saturated.

I really don't want to give them any more money lol

I found the smokeping tool which seems to measure latency over a period of time.  Does anyone have experience with this or other tools I could try?

Thanks for the help!