Beak Boater Posted July 11, 2018 Report Share Posted July 11, 2018 Tried a 17 pitch Mercury Spitfire 4 blade on my RF 18. Its powered by a Yamaha F115. Boat is a 2014, fuel tank is full and mounted in the front of the boat, 3 batteries, 2 Gp 27 trolling motor, and a Gp 31 house battery. All batteries mounted under the console. Trolling motor, Powerpole, fishing gear, Ect. 2 People Boat ran 42 mph at 5700 rpm. The prop that was on the boat was a K16, I had bought the boat used. It was severely under propped when I fished with one person. Cruise rpms were too high for me, and full throttle would hit the rev- limiter tach showed 6400, didn't know they would spin that high. Spitfire performed as advertised, good cruise mpg, about 5 according to the gauge at 30 mph, no cavitation in the turns, boat gets up on plane without tabs, doesn't labor just comes right out with the motor trimmed down. If you over trim these boats they seem to want to hop. The 4 blade reduced that noticeably. I could still make it do it if I trimmed it high running slow, but the 3 blade K16 was a lot more sensitive to trim and you would have to keep the trim tucked under unless you were running fast. The Spit Fire is a good all round prop. Would like to see about 300 more rpms, will wait until the fuel load burns off and see what effect it has, if any. May decide to have the prop worked a little and see what other results I can get. Link to comment Share on other sites More sharing options...
lurem Posted July 11, 2018 Report Share Posted July 11, 2018 Looks pretty good to me! Nice work! Link to comment Share on other sites More sharing options...
Beak Boater Posted July 11, 2018 Author Report Share Posted July 11, 2018 2 hours ago, lurem said: Looks pretty good to me! Nice work! Thanks,.....it was your recommendation in another thread that sparked my curiosity in the Spit Fire. I have no jack plate, motor mounted as low as it will go. Have you experimented with motor height? Is their anything left to gain, or is it pretty much try it and see type of thing. I know they are not rocket ships....but I like to tinker and maximize my set up......you know........for fuel mileage. lol Link to comment Share on other sites More sharing options...
lurem Posted July 11, 2018 Report Share Posted July 11, 2018 Tinker away! Raising the engine one notch at a time will make small changes and will not hurt as you can lower it back down if it has adverse effects. You can raise and lower the motor in your garage with a floor jack, small piece of flat wood, wrenches, sealant to re seal the holes and using the tongue jack on your trailer. PM me if you want the details and I will call you. It may get the extra RPM's you want, but may cause it to blow out. Just have to try it and see. you commented "If you over trim these boats they seem to want to hop". When I run I trim as high as I can till I get a little hop then 'barely' bump the trim tab button. Not enough to slow me down but just enough to settle the nose. That way you can cruise faster and keep the motor trimmed for better efficiency (sp?). Give it a try and see if it works for you. Link to comment Share on other sites More sharing options...
Beak Boater Posted July 13, 2018 Author Report Share Posted July 13, 2018 Thanks Lurem.....guess I should have worded my question a little better. I was looking for results that you or other saw by changing the motor height. I have moved them before but appreciate the advice on how to do it. How many RPMs did you gain if any, Cavitation or water pressure problems. Just being Lazy.....instead of changing it myself, trying to get others results to decide If I want to do it. I figure Hewes experimented with motor height and mounted it at the best position. May just add a jack plate, I have the short platform and the cowl may hit If I don't pay attention. Link to comment Share on other sites More sharing options...
mnelson92 Posted July 17, 2018 Report Share Posted July 17, 2018 just put the x7 17 pitch on my 2003 redfisher with the f115 and got similar results. 44 mph wide open throttle with me, finance and 95lb lab and 3 battery's. loaded down with 4 people I was getting 40 mph. The biggest thing for me was the handling, it is night and day better than my old power tech three blade. Like you said, mine is less subjective to porpoising at high speeds when its not trimmed just right. Link to comment Share on other sites More sharing options...
VsteveV Posted July 17, 2018 Report Share Posted July 17, 2018 4 hours ago, mnelson92 said: just put the x7 17 pitch on my 2003 redfisher with the f115 and got similar results. 44 mph wide open throttle with me, finance and 95lb lab and 3 battery's. loaded down with 4 people I was getting 40 mph. The biggest thing for me was the handling, it is night and day better than my old power tech three blade. Like you said, mine is less subjective to porpoising at high speeds when its not trimmed just right. Do you have a jp? Link to comment Share on other sites More sharing options...
mnelson92 Posted July 20, 2018 Report Share Posted July 20, 2018 On 7/17/2018 at 7:40 PM, VsteveV said: Do you have a jp? yeah i have a bobs 6" hydraulic jackplate. The three blade just wouldn't grip trimmed up and would still porposise pretty bad. I actually gained 3 mph by switching to the x7 4 blade from my powertech 3 blade. Link to comment Share on other sites More sharing options...
VsteveV Posted July 21, 2018 Report Share Posted July 21, 2018 From what I understand at some point (not sure what year) MBG moved the fuel tank slightly forward. Besides that our boats are the same I assume? And rigged similar. I need a new prop badly and that x7 has been on my radar for some time! Link to comment Share on other sites More sharing options...
mnelson92 Posted August 1, 2018 Report Share Posted August 1, 2018 On 7/20/2018 at 8:13 PM, VsteveV said: From what I understand at some point (not sure what year) MBG moved the fuel tank slightly forward. Besides that our boats are the same I assume? And rigged similar. I need a new prop badly and that x7 has been on my radar for some time! I highly recommend the x7. I absolutely love it. I got a really good deal on mine as well from offshore performance specialties, paid 543$ out the door with the fl torq hub included. Link to comment Share on other sites More sharing options...
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