The 18 hull really shines at 22/23mph in rough water and 27 mph in calm water. Don't overpower it . . . just keep it light. 115/130hp yamaha is perfect. When it gets rough and you have to slow down to 18 - 22mph (doesn't matter what engine is on the back) . . . A smaller motor tends to be in a happier place along it's powerband than big heavy motor turning a 21pitch prop 2500rpm and sucking wind.

The weight difference from the 130 Yam to the 150 Ocean Runner is only 30 lbs +/-. Depends also on what year 18SF 80-87's are heavier boats and the slightest extra weight will be magnified

thanks again, this is an old 18SF. I'm really torn, about the going between the Johnson and Yami/Suzuki. The Johnson is an older work horse that I know runs and is reliable. Friend of mine, had it on an older whaler wants to unload the engine for cheap cheap. Might be leaning that route so I can just get out there and fish. Maybe consider a repower down the road. thoughts?

X 2. Although it does seem the the faster you go the better it rides. I can hit 42 - 44mph with my 150 ocean runner in anything less than 2' ers. With that said, I would bet that a bare bones 18 would be out standing with an old 70 Johnson in the really rough stuff...

Although I'm biased towards lighter motors, the financial side is easy. Just convert the price difference between the Yam/Zuke and the Johnson into gallons of gas. Then use the gas mileage differential to figure out how many miles or years you'd have run the more efficient motor to save that much gas. If it would take many miles/years for the more efficient motor to pay for itself, it might be hard to justify. But you also need to consider how you'll use the boat and in what sort of seas. If you spend much time in rough seas, the fuel cost may be less important than ride quality, which would point you to the lighter motor. Regardless of what motor you pick, mounting height and prop selection make a big difference in performance. A good stern lifting 4 blade prop and Doelfin or equivalent plus trim tabs that will help you hang on plane at low speed can help partially offset the weight of a heavy motor.

I agree and it will be fine - just de-carb it first thing - google Dunks Method

OMC's really need it