If your at around even with the pad works for lots of props. Some like it higher some like it lower. Its realy a seat of your pants and GPS reading. If your even or 1/4 below I would just start testing there. You can start by having a round about base line for pitch and setup rpm ranges to be with in based on 7-9% slip to be safe. Say your speed on a set up like yours with a 26 at 8000rpm 1.87 gears and 7% is suposted to do around 98MPH. Start at 1/4 below and try to get close as you can without going to poss on the trim. If your RPM increases and your GPS speed doesnt go up, your one or two bumps to possitive for your trim at that hight and reached only say 94mph? If all felt cozzy and the bow wasnt doing anything like dropping to one side or starting to lower try raiseing the engine one more bump and try it again. The key is to not over trim and knowing were nutral trim is. Its good to know from all down how many bumps it takes to reach nutral. Mine is 14 to nutral and a fast hole shot is 8 bumps from down were it doesnt take but two or three more be on the pad at over 70. From there its finess and feel untill my rpm goes up a hair and my speed doesnt. Then I know thats max for that hight above the pad and Im just starting to surface the prop to much creating to much slip. Im going out tomorrow and testing a prop this way again. Once I get to know what the top speed with just me in the boat and were the engine hight is maximized I write it in my little book I keep onboard incase I forget. This way I know that at this hight with this prop I go X mph under perfict conditions and can ussuslly duplicat the top speed to tee most any time. If its hotter out or water temp are higher humid ect.. then I expect a little slower by a mph or so and dont bother trying to get there on those days.
Just be safe and go about it methaticaly as long as your comfortable. If your not feeling good about it then your probably at the wrong hight.
Test each prop starting from the same base line each time untill you find the spot your comfy with and just stay there for a while. On a brave day you might try to top that speed in the spring or late fall when temps are lower. But generaly I try to get close to what the expected speeds are for a given pitch at a conservitive hight. Ive found 7% seems to be the norm but have a few props with less but none with more slip than 7.
This my plan for tommorow. Ive got a 28 drag4 to try. Im expecting around 7200RPM. I have 1.87 gears with 7% slip I should be getting 94.9 out of it. The lake is at 2300ft above sea level so I subtract 5% for altidude. Ill try it first at even with the pad because I know that drags can handle higher shaft hights. Ill try and get to 85 then one bump at a time and holding it letting the speed build each time before i bump it again. When I notice the rpm go up and the speed stop Ill back off. If my speed was only say 88MPH Ill raise the motor a bump then try again the same way. Ill try and get to were the rpm goes up and the speed doesnt again or if I reach 7200 rpm and am going 90 before this happens Ill be happy with that and call it a wrap. Note were I had every thing so next time I use that prop I know what the limitations are. Ive had some props were I am 3/4 above the pad and they feel good. And some like stock trophys that need to be 1/4 below to even at the highst or they are slower. The cup, diamiter and a lot more play a role in were your prop shaft hight should be.
The bottom line is highest hight with nutral trim and max speed equals perfection. Youll go threw 10 props to find one sometimes that accually meet this critiria. Be extra safe with your 280 and only go as fast as you feel comfortable with. Dont expect to run 104 untill your comfortable at 100 a hole bunch of times. Speed is relitive. You get used to it and always want more.:banghead
