3.5hp 4 stroke

I understand these motors are the same across the Tohatsu/Mercury/Mariner brands and have been offered one at a reasonable price circa 2014 which id like to run as an Auxillary for my 17' Boston Whaler and my kids to learn on a small inflatable.

The chap says it runs but "needs tuning" hes not been any more/less specific but says it starts but runs a bit rough.

Are these engines fairly robust and reliable? and anything that is common faults for me to check first of all?

The MFS2.5/3.5 is shared across the Tohatsu, Nissan, Evinrude, and Mercury lines. Tohatsu makes them all. They are splash oiling (no oil pump) and they have a single-piece ignitor, as opposed to a separate coil and CD, making the ignition very reliable. The A version dates from about 2006, and the B version from about 2009, and is current production. These single-cylinder, low-mass motors must idle fairly fast to prevent stalling when shifting into gear, but that's about the only caveat to running them. They have a sight glass for the crankcase oil level, and that level must never ever be even slightly over full.

About the only "tuning" these get is oil and LU lube changes, carb cleanings, and fresh plugs.

thanks Paul, usually "needs tuning" means motor is finished! hoping its just the usual case of left to stand with fuel in the carb and just needs a carb strip and clean.

Any idea if this would push a 17' Whaler as an emergency auxillary?

I clean those carbs with a 6-hour soak in a heated ultrasonic tank filled with carb dip. Very hard to clean the small passages. Spray carb cleaner is not aggressive enough.

It will *move* a 17 foot whaler, but won't really push it well. We use them on small sailboats an maybe 8-foot dinghies.