Reported by Dutch Skipper Gerard Westemijer:
Harbour Fees here (January 2018):
There are just a few berths available in the Marina and the price for a 15m yacht is Dhm 365 a day. The harbour master of the commercial harbour asked for a 15m yacht – Dhm 275 a day. So this is altogether a really expensive harbour.

We stayed in Mohammedia in November 2017. We were sent away from Rabat because of the onshore winds – they noticed us approaching on AIS and called us well in advance to ask us to proceed to Mohammedia. We arrived at night and there was no space so we were tied up alongside a moored boat. The officials arrived directly and were very friendly and efficient. There was no drug sniffing dog or any boat search. We payed Port Authorities 26 euros a day, and the marina just raised their price from 4 to 25 euros per day! Way too expensive for us to stay long. It is such a shame, we were planning to stay at least a week but now we only stayed 3 nights. Mohammedia has great facilities and the city has a good train connection to all the major cities in Morocco. Diesel 10 Dirham per L, the same price as in Europe! Gibraltar is way cheaper.
We checked out the marina in Casablanca as well, that look like it needs an investor. It probably won’t open soon.

Posted on behalf of SV Proteus:
It was no problem to anchor just outside the harbour at first (or even for a night) – in about 4-5m just off the public beach – and go in with the dinghy to check in with immigration/customs, and wait for a spot in the marina. The holding is good in sandy mud. If you’re really wanting a space, just wait an overnight: the turnover is usually quick.

Because of the adjacent petrochemical port, security is extremely tight. Actually, surprisingly tight. They require a shore pass to get out and back in to the port outer gate. There is a Carrefour (and a liquor store!) in town and the taxi ride is super cheap: around 10 dirhams.

Fuel was possible, but if your boat is deeper than 1.5m, the fuel pump is only accessible at high(er) tide.