MOROCCO 28 Mar 2015 (AFP) - Overnight leader Ramsay carried a one shot advantage into the 18th hole before a wayward tee shot led to a bogey as the Aberdeen native fell into a tie with McArthur and 24-year-old Wattel.
Ramsay, who is looking for a third victory on the European Tour but has struggled for form this year missing four cuts in five tournaments, limped home with a one under par 71 on the day while McArthur carded a 67 that included an eagle and five birdies.
"My ball striking at times was excellent, I just couldn't make any putts," said Ramsay.
"I didn't really make anything out there today. I'm pleased to be in the hunt. I'm a fraction frustrated as I played some great stuff out there."
Wattel also moved top of the leaderboard as the right-hander from Montpellier shot a superb round of five under 67 with six birdies and an eagle.
The Frenchman picked up four shots over the final four holes.
"It was a thrilling back nine," said Wattel who is looking for his first European Tour victory.
"I'm desperate for a win. I can't control what the other guys will shoot so I just concentrate on my own game. We will see tomorrow (Sunday)."
Seven golfers are tied for second on six under including Argentine Emiliano Grillo, 2011 winner David Horsey, fellow Englishman Richard Bland as well as Denmark's Soren Kjeldsen, Irishman Kevin Phelen and South African pair George Coetzee and Jaco Van Zyl.
A double bogey on the 18th cost Van Zyl valuable ground and the outright lead.
Grillo was another player to shine on the picturesque Golf du Palais Royal with a 67, that included just one bogey, as the stage is now set for a thrilling final day.
"Hopefully I will have a chance tomorrow. I have made 17 birdies so far so there have been a lot of mistakes out there too," Grillo told europeantour.com
"It is a course where you have to be on your game. I had it today (Saturday) except for one shot. It was a great score though and it gives me a chance tomorrow."
Leading third round scores on Saturday in the European Tour's Trophee Hassan II (par 72):
209 - Richie Ramsay (SCO) 72-66-71, Andrew McArthur (SCO) 71-71-67, Romain Wattel (FRA) 68-74-67
210 - Richard Bland (ENG) 69-70-71, George Coetzee (RSA) 67-72-71, Jaco Van Zyl (RSA) 69-71-70, Kevin Phelan (IRL) 70-70-70, Emiliano Grillo (ARG) 74-69-67, Soren Kjeldsen (DEN) 68-73-69, David Horsey (ENG) 70-71-69,
211 - Wade Ormsby (AUS) 71-72-68, Michael Lundberg (SWE) 70-75-66
212 - Rafa Cabrera-Bello (ESP) 69-69-74, Pablo Larrazabal (ESP) 70-69-73, Oliver Farr (WAL) 70-68-74, Anthony Wall (ENG) 68-72-72, Max Orrin (ENG) 70-70-72, Shiv Kapur (IND) 72-73-67, Bernd Ritthammer (GER) 71-70-71