Fishician Posted January 24, 2018 Report Share Posted January 24, 2018 I have a question. I am going to re power my 2015 16 ft Redfisher with a 115HP Yamaha 4 stroke. I currently have it powered with a Yamaha 90HP FS. How much draft can I expect to lose with everything else being equal. The new motor will be 24 lbs heavier, And how much of a drop off in MPG? Thanks so much for your input Link to comment Share on other sites More sharing options...
F1sh0n Posted January 24, 2018 Report Share Posted January 24, 2018 Is your 90 a 3 cylinder or 4 cylinder? I ask because the new 90 is a inline 4 cylinder and the 115 only weighs about 25lb more which should be pretty negligible. Link to comment Share on other sites More sharing options...
dabear Posted January 24, 2018 Report Share Posted January 24, 2018 1 hour ago, Fishician said: I have a question. I am going to re power my 2015 16 ft Redfisher with a 115HP Yamaha 4 stroke. I currently have it powered with a Yamaha 90HP FS. How much draft can I expect to lose with everything else being equal. The new motor will be 24 lbs heavier, And how much of a drop off in MPG? Thanks so much for your input Your gas mileage may not drop because you can run the same speed at a lot lower RPM with the larger HP motor . I would think you could cruise at about 32 MPH at about 3800 RPM with the SHO 115 . If you near the Tampa Florida area Family Boating does repower jobs and may be worth checking out. Link to comment Share on other sites More sharing options...
Fishician Posted January 25, 2018 Author Report Share Posted January 25, 2018 Thanks for your response. My current 90 HP Yamaha is a 2015 a 4 cylinder. It only has 60 hrs on it but there has been a problem with the Check Engine light registering a #37 fault. It has been in the shop for this problem 4 times in less than 3 years. I simply can not trust it on a trip to Flamingo. New 90 four strokes are nowhere to be found, but 115's are more readily available and thus the decision is easier. My mechanic has been in touch with Yamaha and they admitted to a problem with #37. Thanks again for your help Link to comment Share on other sites More sharing options...
geeviam Posted January 25, 2018 Report Share Posted January 25, 2018 6 hours ago, Fishician said: I have a question. I am going to re power my 2015 16 ft Redfisher with a 115HP Yamaha 4 stroke. I currently have it powered with a Yamaha 90HP FS. How much draft can I expect to lose with everything else being equal. The new motor will be 24 lbs heavier, And how much of a drop off in MPG? Thanks so much for your input I have a 2017 Redfisher 16 with a Yamaha 115 SHO. What Dabear said is spot-on. Like he said, the 115 doesn't have to work as hard for the same speed so the MPG is probably the same or better. My motor gets 7.4 MPG at a 3800 RPM cruise. The propeller you run with is very important. I can't say for sure what the difference in draft will be after installing a 115 FS, but I doubt it would be very much since the Redfisher has such a wide beam. Just some free advice you might consider, for the best performance and handling: I suggest adding wedges between the motor and transom for extra negative trim when needed, to help with stability, hole-shot and propeller grip - like these: http://thmarine.com/cmc-transom-wedges-2-degree Also, if you do not currently have trim tabs, you will want them for additional ride control when you install a 115 FS on your boat. If I was looking to buy trim tabs today, I would buy Bennett BOLT Electric Tabs. Just some suggestions and opinion of course. These extras cost a little more but it's money well spent. Link to comment Share on other sites More sharing options...
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