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Prop selection

goose

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"Still messin' with my V-P

"Still messin' with my V-P 250. I have a 14-15 on her now. When I ran her yesterday I got 5600 RPM@WOT, tooo many R's for me. I'd like to bring it down to a MAX of about 5000. If I swap out to a 15-17(which I have on hand), what would be the result? Am I going the right direction to reduce RPMs, is this gonna be another trial and error game? LOL
I don't mind T&E but it's a 40 mile round trip to the lake."
 
"I read that 1 inch of pitch i

"I read that 1 inch of pitch is equal to about 200 RPM so 15 to 17 should reduce the RPM 400, I'm not sure what going from a 14" prop to a 15" prop will do, also decrease it but by how much."
 
"Thanks Dave,, I think it will

"Thanks Dave,, I think it will get me in the ballpark. It's on, I'll let ya'll know how it works out tomorrow hopefully."
 
"Dale, if your outdrive has po

"Dale, if your outdrive has power trim, you may want to test different settings and see if you can improve your top end RPMs.

Selecting the right prop is a combination of art and science. What I normally do is run the boat with whichever propeller I have and, depending on the results of the test, calculate which propeller dinensions would give the best performance. However, there are so many props around (wide blade, narrow blade, highly skewed, high rake, no rake, cupped, uncupped, etc) that sometimes it takes a few tests to find out which one works best for you. Additionally, I take with me a GPS and a fuel flow meter to measure top end speed and fuel consumption per mile. All those factors will determine which propeller I settle for.

As a rule, I tend to use propellers with wide blade, a good rake and heavily cupped, as I have found they work best for my application. I am lucky to have in my area a propeller shop whose owner does not mind letting me try a few used propellers, as he knows I normally end buying one or two of them (or asking him to modify them to suit my needs)."
 
"I am learning as I go here. I

"I am learning as I go here. I hadn't planned on all this stuff when I bought this yatch, but so far I'm enjoying it, it's getting a little pricey, but still enjoyable .
This 250 doesn't have power trim, and it has the same reverse kick-up problem alot of them have. I've been reading through old posts and I'll tackle that one later.
I'm more concerned with engine longevity than speed. I fish, no skiers, no tubes, no rush to get there(or back). If I can get 30MPH from her, unloaded, I'll be happy. I tried taking my laptop w/GPS yesterday, but couldn't see the screen for the glare. I have access to a handheld, but nobody I know has a flow meter, I'll have to test the milage the old fashioned way. Whatever I end up with, I'll have to live with it for this season, I'm starting to hide CC recipts from the boss, LOL."
 
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