Whodat Posted April 20, 2020 Report Share Posted April 20, 2020 Looking to repower my 2001 17 HPX V with a 90 hp Yamaha 4 stroke. I have the 90 hp Yamaha 2 stroke now. Does any one know if I would have to modify the poling platform due to the new motor being taller. Has anyone done this change? Did it perform better, worse or the same? Quote Link to comment Share on other sites More sharing options...
chad1616 Posted April 24, 2020 Report Share Posted April 24, 2020 I just redid my same year hull. (you can see it under 17 Hpxv remodel )I had to completely rebuild platform for 115 vs 90 2stroke . Steering was limited and definitely height. As far as performance goes to 92 stroke still outperforms the new 115 SHO on holeshot but im still in prop testing phase . My topend is way better . 52 heavily loaded in poor weather Quote Link to comment Share on other sites More sharing options...
Whodat Posted December 23, 2020 Author Report Share Posted December 23, 2020 I'm still trying to decide what engine to get for a repower 17 HPX-17 (2001). My 90 2-stroke is shot. Has anyone gone from the 90 2S to the F70? I see the bulletins, but my 90 2S never matched the bulletin (only got max 40-41 mph vs. 47 ish). The 115 is definitely off the list. If F90 means modifying or replacing the poling platform, than that might be another reason to go to the F70. Will I really get 40-41 mph out of the F70 like the bulletin says? If so, that would match what my old 90 2S did and I guess I can live with that. 1 Quote Link to comment Share on other sites More sharing options...
hawg Posted December 25, 2020 Report Share Posted December 25, 2020 I can't say about platform clearance but the performance of my Yamaha F-70 on a 2001 HPXV is nowhere near the claims on the performance bulletin. Light loaded, I can get 35 MPH at 6000 RPM. NEMA 2000 fuel burn at that power setting is 5.7 MPG. Normal cruise for me is 5000 RPM, 30 MPH, 7.0 MPG. Quote Link to comment Share on other sites More sharing options...
Whodat Posted December 30, 2020 Author Report Share Posted December 30, 2020 Thanks Hawg! I don't think I can live with those actual mph numbers from the F70. Looks like I will go with the F90 and modify the poling platform if I need to. Appreciate it. Quote Link to comment Share on other sites More sharing options...
hawg Posted December 30, 2020 Report Share Posted December 30, 2020 I'll likely upgrade for the same reason. I'm guessing the fuel economy won't suffer with the larger engine not working as hard as the F70. My concern is the added weight of the new engine. Quote Link to comment Share on other sites More sharing options...
Sudolicious Posted January 19, 2021 Report Share Posted January 19, 2021 I am in the same situation. Did you go with the 90 or the 70? I am more concerned about the additional weight of the 4 stroke versus the 2 stroke 90. Quote Link to comment Share on other sites More sharing options...
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