Outboard Motors: 3.5 hp vs 6 hp

When you live on a mooring or an anchor the dinghy becomes your most important piece of daily equipment, and the choice of how to power your “car” is very important.

The place that I am moored (between Fleming Key and Dredgers Key outside of Garrison Bight in Key West) is exposed to the North and North Easterlies in wintertime. This can lead to motoring to/from your boat in 20knot winds with a couple of feet of swell. My commute each way to shore is about 1 mile. This is an hour if you row (yes I have), 20 minutes with a 3.5hp and 10 minutes with the 6hp. In the summertime this is a convenience, in the wintertime, it means you’re exposed to bad conditions for less time, less time for bad things to happen.

Other than speed, here are some other differences between the Tohatsu 3.5hp and the Tohatsu 6hp 4 stroke motors.

Cost: The 3.5hp was around $800 last november. The 6hp was $1400

Fuel Capacity: The 3.5hp has a gas tank that holds a quart of gas. This is good for about 45 minutes run then you have to stop and refuel. Sometimes if you run out when exposed to a swell it can be interesting to refill the tank while bouncing around in your dinghy. I kept a 2.5 gallon gas can on the dinghy as it was easier to use vs a 5 gallon can and would last about 2 weeks of daily commuting. The 6hp comes with a 3.5 gallon external gas tank. This usually runs me for about 3 weeks between refills. Using the good gas (expensive) that means my monthly fuel bill is about $12

Gearing: The 3.5hp has only forward gear, though the motor will turn completely around to go in reverse (but man it’s hard to steer that way). The 6hp has forward/neutral/reverse. A convenience when your gunkholing or on a crowded dinghy dock.

Low Water Running: The 6hp has a setting which will allow you to raise the motor partially. This will allow you to run in about 6 inches of water. Great for skooting around the backcountry keys.

Propeller: The 3.5hp comes standard with a plastic propeller. I upgraded to the aluminum propeller but found that it made the engine run hard all the time, even though it did give me 0.5 mph more speed. The 6hp comes standard with an aluminum propeller which I like.

I know when I first started thinking about getting a motor I was concerned that a 3.5hp wouldn’t be enough for my dinghy ( a West Marine Standard Dinghy, 9.9″ long hard dinghy). It is, but the 6hp allows you many more options in ease of adventuring, speed for your daily commute, and