Hey guys I’m about to start an xf22 build, I have build boats using this method in the past an beefed up the transom an stringers to mount a higher hp motor.
Was wondering if anyone has any experience or input with this hull/build in regards to what would be needed to mount up a 300hpdi Yamaha
Xf22 flats build
Re: Xf22 flats build
Boats are built for a range of motors and the designer(Jacques) designates this, I will try to explain why your 300HP willl not work. The recommended HP for the XF22 is 115HP for top speed. The top speed with this HP will put you in the mid-30's depending on load. The Yamaha 300HP weighs 200lbs more than the 115HP. Adding this much HP and weight will require a complete redisgn of the XF22. Not only the stringer and the bottom, but the amount of fiberglass, the thickness ot the frames and stringers and transom. And then the spacing of the frames and stringers.
I am doing a calculation for you here: The COG is calculated frome about 6" behind the helm at the waterline. So on this boat it looks to be 8'. To compare the 115HP to the 300HP we use 200lbs x 8ft or 1600lbs. That is the amount of lbs that need to be moved forward of the COG if you go with the 300HP motor. Just another example of things that you would need to be taken into account of if you go with a 300HP motor.
I just ran my calculator with the Yamaha 150 and top speed was 44mph. The 115HP top speed was 38mph. I do not know about you I don't want to drive a flat bottom at speeds above those speeds. I have an OD18 which is flat bottomed and I keep it in the high 20's though it will hit the mid-30's. Oh, I forgot to mention the 300 would reach a top speed in the low 60's, it would tear the boat apart as designed now.
I would suggest sticking with a 115 or a 150 with an extra layer of 12 or 17oz biax on the bottom.
Well good luck to you. Please creaate an account so you will get the best advice available.
Jeff could you refer this to Jacques. Want to be sure.
Tom
I am doing a calculation for you here: The COG is calculated frome about 6" behind the helm at the waterline. So on this boat it looks to be 8'. To compare the 115HP to the 300HP we use 200lbs x 8ft or 1600lbs. That is the amount of lbs that need to be moved forward of the COG if you go with the 300HP motor. Just another example of things that you would need to be taken into account of if you go with a 300HP motor.
I just ran my calculator with the Yamaha 150 and top speed was 44mph. The 115HP top speed was 38mph. I do not know about you I don't want to drive a flat bottom at speeds above those speeds. I have an OD18 which is flat bottomed and I keep it in the high 20's though it will hit the mid-30's. Oh, I forgot to mention the 300 would reach a top speed in the low 60's, it would tear the boat apart as designed now.
I would suggest sticking with a 115 or a 150 with an extra layer of 12 or 17oz biax on the bottom.
Well good luck to you. Please creaate an account so you will get the best advice available.
Jeff could you refer this to Jacques. Want to be sure.
Tom
Last edited by TomW1 on Thu Jun 16, 2022 8:52 pm, edited 1 time in total.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978
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Re: Xf22 flats build
I wrote a long reply but it got lost in the cloud
Does not really matter as Tom has covered 90% of what I wrote.
If you do build this boat we would still enjoy seeing a build thread
Does not really matter as Tom has covered 90% of what I wrote.
If you do build this boat we would still enjoy seeing a build thread
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Re: Xf22 flats build
Building beyond the designer's specs requires special mods by the designer.
XF22 is a nice looking boat, but not gonna do well with 300hp, probably end up killing the helmsman.
XF22 is a nice looking boat, but not gonna do well with 300hp, probably end up killing the helmsman.
Re: Xf22 flats build
Did not want to say that fallguy, but with most of the weight aft hitting a wave wrong could easily cause it to flip. Tomfallguy1000 wrote: ↑Thu Jun 16, 2022 8:47 pm Building beyond the designer's specs requires special mods by the designer.
but not gonna do well with 300hp, probably end up killing the helmsman.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978
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Re: Xf22 flats build
Cast iron testicles ?Guest wrote: ↑Thu Jun 16, 2022 3:32 pm Hey guys I’m about to start an xf22 build, I have build boats using this method in the past an beefed up the transom an stringers to mount a higher hp motor.
Was wondering if anyone has any experience or input with this hull/build in regards to what would be needed to mount up a 300hpdi Yamaha
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Re: Xf22 flats build
That's part of what it would take to drive this thing but like Tom said, you hit a wave wrong and it doesn't matter what they're made of. I've had a boat go sideways on me at 50 mph and it's only by God's grace me and my kids weren't hurt. A 150hp on the XF22 would be the most you'd want on this thing and that's still a lot. Still curious what Jacques would say though...BarraMan wrote: ↑Fri Jun 17, 2022 3:19 amCast iron testicles ?Guest wrote: ↑Thu Jun 16, 2022 3:32 pm Hey guys I’m about to start an xf22 build, I have build boats using this method in the past an beefed up the transom an stringers to mount a higher hp motor.
Was wondering if anyone has any experience or input with this hull/build in regards to what would be needed to mount up a 300hpdi Yamaha
Boats restored: 1973 Glastron CV16, 1990 Proline 17 CC, 1993 Bass Boat
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
Boats built: custom 15ft flat bottom skiff, Soon-to-be-built TX18 (originally dborecky's build)
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Re: Xf22 flats build
150 horsepower is excessive. The boat is going to run out and handle great with a 90-125 hp motor. Make sure you put some strakes on the hull bottom which will enhance maneuverability big time. The more power you add, the worse this boat will turn.
Richard
Completed boats...XF20 "Red Alert", Aripeka Angler's Strip Canoe, FS18 “Bare Bones”, GF12
Currently building...PY12 Kayak
viewtopic.php?f=12&t=62146
Completed boats...XF20 "Red Alert", Aripeka Angler's Strip Canoe, FS18 “Bare Bones”, GF12
Currently building...PY12 Kayak
Bare Bones build thread...If there is magic on this planet, it is contained in water. - Loren Eiseley
viewtopic.php?f=12&t=62146
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Re: Xf22 flats build
Put the recommended engine on the boat. Buy some 300hp stickers from your engine manufacturer and put them on the cowl. Brag to admirers on the ramp that Yamaha built you a special turbo supercharged 300hp and you are testing it for them. This boat will go as fast with 115hp as any production boat with 300hp. The money saved will buy your gas for the life of the motor.
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