Logic says the higher you get the prop out of the water the easier it is to turn. What sort of RPM gain do you get with every 1/4" you go up?
Logic says the higher you get the prop out of the water the easier it is to turn. What sort of RPM gain do you get with every 1/4" you go up?
Not sure, but at a point you lose lift and then rpms go down again because of the additional friction/load. Also, safer to move 1/16" or 1/8" at a time 1/4" is a bit amount. With the opti, on my xb21 I lose water pressure before losing lift with 10" setback..
Agree with the logic, but on my boat its a really difficult thing to measure in 1/4" increments. On my boat two 1/4" increments low translates to a boat that runs crappy up top. The motor is just too deep and the entire performance of the boat is off. Less RPM related and more setup. Example, if I had 100mph prop on it will run 93-95 1/2" deep but it will feel all out of sorts and unless I was going for some sort of data collection out of the run I probably would have backed off at 85 when I felt things were off.
It would be interesting to log. Next time I'm down I will set up the logger and see. It would be neat to see how the speed picks up with the RPM. I would imagine the slip and water pressure will both be falling along the way with each bump of the plate. It would be cool to see how long it takes for the speed to pickup and settle off as well. Probably take a really nice day so we can run a few miles and let the boat level off at each bump of the plate. I will just move the plate one bump and see how much it moves (Probably 0.06-01"). Then log from 1/2" below my typical running height to .2 over. That's probably 7-10 data points.
Often when I log you can see when the trim is hit. The speed will jump up. Changing water conditions has the same impact. Sometimes if I look at the logger overlaid on google maps I can see the speed pick up when I hit the "good patch" of water. This kind of stuff is what makes it difficult to get a good number. Was it the motor height or changing water conditions that resulted in the change.
Allison XB21 2+2
Mercury 300R
LOL, it looks like Nathan and I were thinking the same thing.
Allison XB21 2+2
Mercury 300R
So, I have a Hydrodynamics plate and it moves up at 1/4" increments. I removed the lip because I was running a 3.0 liter on my 2003. I am at 1/2" above now and have over 20PSI water pressure. Also, I have 15" of set back. I have spoke to several people with a similar set up running 1" over with no problems. I have lots of lift running a Pro Max 26 that Robby work for me. Anyway just wondered if anyone knew what the standard RPM increased was with motor movement. You know like with props when you go up in pitch size the general rule of thumb is 200 rpm for every pitch up or down.
I would try a 28 Promax with proper venting not much holeshot change....At least when going from 28 to 30 with my 1.75 gears. Ill have to assume that 26 means you have 1.62 gears. Make sure it will bent to 4200/4400 is all.
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