Thanks Joe, its fast but then again the Bezoats its on is always fast. It weighs in at about 430# including me. The Yamato foot is les than 2" wide & 3/4 deep at prop shaft center. A good running stock used powerhead would make about 58-59 on that tower so 65 is realy only up about 6mph. Thing is I know theres more. Whether to spin more prop or more R's is the Q. Im guessing it to be about 7200 to 7500 now.
Eric.. When you look at various 2 strokes theres motorcycle motors with ridiculous power, so why not outboards? They need the torque & have to trade off some hp to get it. Water resists almost 800 times air. A set of wheels on pavement rolling on bearings is nothing compared. An outboard has to be tuff-r too for the rigors of being run like its always going uphill. If you took a really hot MC motor removed the 5 speed gearbox & attached it to a prop it would not be likely to get the boat over the hump & on plane. That being said the best thing is for it to be right, piston clearaces, ring gaps, tuning the list goes on. Check your 20 over for built in restriction, I run time at about 29 30, never saw much difference as long as its 30/35. the motor I mentioned with the wiseco's & 3 cyl rods has 150psi with a regular head cut a bit.
When I got my Airborn done I started out with a 22ci 25hp OMC. had it running nice but was stock. It did about 33 tops. Then I got a 31.8 [big block]. It's very similar, like a big cuz. That made 36 1st try & the torque was a seat buster LoLs Keep in mind thats a flat bottom racing runabout at about 475 total. I stared messing with carbs & set up & props, tweek-d it up to about 39, & actually got a 40 once. [It was a conditions permitting moment] Then I got my hands on this 13.5 P 2 blade righty speed prop. I adapted it to an old club foot
Yes, its modified a bit but is still 12:21 That made 44 1st try then 46.1 soon after. [Some said 'that'll never go'] Its on my pals hydro now & has made 52gps at about 500# @ well over 7G's.
That's about where I stopped working with stock gearcases & never had a thru hub 31.8. for all the work done I have to say besides putting a racing gear case on & running it on a race boat, the most speed Ive ever seen gained was from a prop & subsequent set up change. Theres 2 ways to approach boat motor performance.. you either turn more R's with the same prop or you spin more prop on more hp. if your 31.8 is open & flowing like a 35 it already has the capability to just a matter of the right prop. over-rev Check also into whether or not you have a rev limiter built into your power pack. thats an easy change.
Joe, I tried to PM you long ago but didn't hear back.. had some Q's
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