Tohatsu 5 2-stroke VS Tohatsu 6 4-stroke

[S/V Antares]

Run a two stroke in a spackle bucket (5 gal) for ten minutes ...surprisingly dirty .... two strokes are a bit lighter but under 6hp no 4 strokes have oil filters so you drop out a pint of oil once a year or so and move on. The fuel economy is worth having a 4 stroke.

[Reefmagnet]

Originally Posted by ontherocks83

Just for perspective on the 4 stroke side my 6hp Nissan 4 stroke burns approximately .5 gallons per hour at wide open throttle. I have a 3 gallon tank and it lasts me about 6 hours.

Not sure how that compares with 2 strokes if anyone has info on an equivelant 2 stroke and wants to share.

It was like diesel vs petrol with a rule of thumb that a 2 stroke uses about 30% more fuel. I think this may be better these days for two strokes as my 5hp Yamaha (2st) burns about the same rate of fuel that you quote. Of course this isn't allowing for the type of craft or load being pushed. My motor usually powers a 10 foot aluminium dinghy that planes up to about 130 kg load at full power or above that load weight runs at about 4 knots displacement at 1/2 to 3/4 throttle.

[Celestialsailor]

Originally Posted by Reefmagnet

For that small an engine I'll take mixing two stroke to oil changes and weight any day. Two strokes have more torque than 4 strokes which equals better hole shots. Single cylinder 4 strokes fire once every 720 degrees which equals lumpy running and vibration. I have an internal and external tank and treat the internal as reserve capacity. Rarely use the motor without the external tank.

Sent from my SGP521 using Cruisers Sailing Forum mobile app

Originally Posted by Reefmagnet

For a pusher motor the 4 stroke is best. For a dinghy I think the two stroke wins, given the choice.

Sent from my SGP521 using Cruisers Sailing Forum mobile app

You kinda contradict yourself there...but I can tell you as a motorcycle mechanic in another life, 4 stroke develop more low end torque than a 2 stroke. 2 strokes are lighter and also wear out faster.

[Reefmagnet]

Originally Posted by Celestialsailor

You kinda contradict yourself there...but I can tell you as a motorcycle mechanic in another life, 4 stroke develop more low end torque than a 2 stroke. 2 strokes are lighter and also wear out faster.

Negatory, imo.

You pop a boat out on the plane at higher rpm. 2 strokes are well known for better hole shots in big hp sizes.

That's why a four stroke for a pusher. Lower rpm pushing more weight on a displacement boat, less fume, less fuel used.

Regarding lifespan, I recently sold off a Yamaha 5 hp of the same design as my new one. After 35 years it finally gave up the ghost with corrosion punching a hole through the water jacket. Aside from being cantankerous to start and having a bit of a flat spot mid range, it ran as well as it's identical replacement. I obviously hadn't owned it for 35 years but I'm reasonably sure it didn't spend it's life sitting in a shed. If I can get that life out of the new one I won't be complaining.