Repower for 18'SF
 

Hey guys, wanted to get some opinions on a repower for a 18' SF. Found a 150 Johnson Oceanrunner, going to run compression on it this week. any input or ideas? should I stay away? is this too heavy. any help is huge. thanks

A friend of mine just repowered his 18 with a 140 Zuke 4 stroke, as have a few others, that 150 should weigh pretty close to that

The 150 will fly. It's a little lighter than the 140. Had the 150 have the 140.

Johnson 150 60 degree engines are very strong, and very thirsty if it's a carb motor- just so you know-

Good Luck!

The 2 Yamaha 130's I had on 2 different 18's were the best power to weight for the boat.

thanks guys, really appreciate it. keeping my fingers crossed the compression test is all good. as for burning fuel, the ride is worth it.:D

Our 1978 18 has had a 130 Yamaha since our 2000 refit- that engine was picked and installed new in 2000 because AT THE TIME we felt the Y130 was the best engine choice available on the market at the time- 13 years, and a wall full of pictures is testament to the balance, performance, and durability of the Y130 on the 18. A great combination.

I wonder what the weight difference is between the 130 yam and the 150? I had a 6 cylinder Johnson 185 on my last boat and it was super reliable. It would push my heavy boat over 40 mph. I can only imagine how fast a 150 would push an 18 SC. The down side was it sucked gas like crazy. On my 21 Chris Craft I only got about 1.7 mpg. I now have a Tohatsu 90A (old school carb and very little electrical) on my 18 SC and I love it! I get over 3 mpg and over 30 mph with 2 guys and a boat full of gear.

There was a guy a few weeks ago on the Maverick Boat Co. forum, maybe a month, who had a 130 Yami for sale very nice looking engine. Might be worth looking into.

The yamie is really a 140hp, but the factory under rated it to sell more 150s. 171kg or 376 lbs. The rude 60 degree motahs are maybe their best effort under omc. Strong and 365 lbs. Both are wonderful choices with regard to weight and balance.

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