V20 with a 140 johnson

T

thebottomfish

Member
Looking for some top speed numbers, I have a v20 with a johnson 140 on it, and with my stainless prop am hitting 34mph at my best, the motor is only turning 5200 rpm, but I'm not sure I want to go from a 13 3/8x 17 to a 13 pitch to get in the right rpm, I think that would hurt my top speed...am I right? Convince me otherwise!
I'm not only after top speed here, my cruise @ 4000 is 23mph and I'd really like to bump that up

Thanks!
 
A 17 pitch is to much prop for a 140 on a V-20. You're KILLING that engine with that prop, not figuritively either, actually killing it. Lugging that engine is the number 1 way to DESTROY it. You want it to turn at least 5600 WOT with an average load in it, but I used to turn mine 5900-6000 routinely. I found overpropping killed the economy on that engine as well, it does NOT like to be lugged. With a 140 on a V-20, your cruise numbers are going to involve some RPM's. I would look into a 4 blade to get some blade surface area to help with the mid range cruise, while still allowing it to turn RPM's at WOT. You need a prop to minimize prop slip as much as possible. A 15 pitch 3 blade stainless would be a good compromise prop. And I wouldn't hesitate to turn that engine up to 4400 at cruise. I found 3800 was about as slow as you wanted to turn it at cruise to get good economy.
 
Before putting this stainless on(last weekend) I had a aluminum 13.75x15 on there and that turned 5300 and 31mph, I really just wanted to see how the boat reacted to the switch in stainless.
Definitely a better bite and acceleration, will have to try going down in pitch to get the rpms up.
If I go from a 13.75x15 3 blade aluminum, what should I shoot for as a 4 blade? I assume I decrease diameter and then obviously I'll want to drop pitch. Would an aluminum 13.25x13 4 blade be a good starting point?
 
With aluminum it is a crap shoot. Aluminum flexes ALOT, and many manufacturers are no making them with extra pitch trying to make them run closer to there stainless counterparts. In all honesty I owuld try a 4 blade SOLAS 15 pitch prop if it was mine. I've had pretty good luck with SOLAS props running smoothly, and being good props. Just keep i nmind each brand is going to run differently. I ran a 15 pitch 4 blade MICHIGAN WHEEL prop on my skiff, and it turned 5300RPM's WOT throttle at 35 MPH, swapped over to a 17 pitch SOLAS and I now turn 5700 RPM WOT and top out at almost 37MPH. I will say the MICHIgAN wheel had ALOT more bite in the cruising range than the SOLAS does. If you could find a used MICHIGAN WHEEL APOLLO 4 blade in a 15 pitch to try, I would think that would be a good mix of top end, good bite for cruise, and still give a good holeshot. I know a 17 pitch stainless prop on my 140 would run 50MPH on my bowrider I had it on while topping out around 5700-5800 RPM's(but I topped out 5900 RPM's at 53 MPH with a 19 pitch VIPER on it). The 2:1 ratio in the lower unit of the V-4's does not like alot of pitch, which makes prop shopping tough.
 
Ferm, is your 17 pitch Solas on your skiff also a 4 blade? Getting closer to hanging my 90 etec and been thinking a 17 pitch 3 blade, but have read that 4 blades seem to work good on the skiffs.
 
My current prop is a 4 blade, and I will never go back to a 3 blade on it. It LEAPS on plane with the 4 blade, and actually picks the stern up and holds it. It helped alot with the stern dipping down getting on plane so I can now plane in shallower water.
 
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