Prop change

[New River Rat]

I'm about ready for a new prop, as my blades are practically slivers now. I am not afraid to beat the crap out of my prop, as I fish a river that is full of limestone and dolomite. The prop I have on is a 10" diameter and 11" pitch. I have to get power to the prop in a hurry on occasion for safety sake. I was looking at a four blade, 10" diameter, 7" pitch. I need a prop guru here.I rarely run WOT, and was thinking this combo of numbers would be more like a 4X4 for the shoals I climb.


4 Blade Aluminum 10" dia. X 7" pitch


OLD PIC

 

[Zum]

I'm no prop guru but I do know you should run an outboard at a certain rpm at WOT.
If your not going to run wide open to often maybe it could work,should get you up on plane in a hurry.
I'd look into a tach so I could keep an eye on the rpm's though.One of those tiny tachs aren't that much and could save the life of your motor,if you run a smallish prop.
What size outboard do you have?
Have you tried a tunnel hull or them pods?

 

[Charger25]

A four blade will give a better hole shot and it should pop right up on plane.
But like Zum said gotta be careful of over reving the engine Guys around here have made pitch fork guards for their lower units to fish the upper James.

https://i104.photobucket.com/albums/m196/BruceS_2006/pitchforkpropguard1.jpg

 

[Ringo Steele]

That pitchfork prop guard is a very interesting item! RNE ...git 'er done! :mrgreen:

 

[Wallijig]

I was talking to buddy of mine about 4 blade props.
He said tried one it handled and come out of hole better, but he had no power in reverse.
So if back trolling or back boat off trailer would not think it would would work so good.

Anyone else use 4 blade and notice these issues?

 

[lovedr79]

I just put one on m boat. 9.25x9 launched and planes a lot faster. No noticble reverse changes. I back off the trailer. Careful when losing though. Doesn't take much throttle now

 

[New River Rat]

I very rarely run the river @WOT, and no problem unloading the boat without cranking the engine. I need something that responds with torque to get me out of very hairy situations immediately.

That pitchfork prop guard is a very interesting item!

Pitchforks are a waste of time when it comes to protecting the lower unit. I had that guard machined from 3/8 304 stainless.

 

[Charger25]

Maybe not as much as the guard that you put on but they will help save the prop and shaft. I wacked my 6 hp on a rock and bent the prop,shaft and popped the seal.

 

[turbotodd]

Typically a 4 blade will get you out of the hole faster, stay on plane at a lower RPM, handle better, and if the engine is lifted on the transom, typically a 4 blade will allow a higher mounting height before it blows out.

The extra blade DOES however increase drag, therefore reduces speed...just a little. I noticed just less than 1 mph difference but it's worth it! (25 HP 4 stroke yammie)

I also run a river that will have 200-400 yard runs of 10-20 foot deep water, then immediately it goes from 20 feet to rocks with less than 12" of water (have to get out & pull the boat over if the water is low like it was last weekend). There are a couple shoals that will work your patience for sure. The 4 blade does well in situations like that where you want to run as shallow as possible yet be able to jump up on plane quickly.

I run a Solas aluminum. They also make them in SS, and the SS 4 blade props are a bit faster than the aluminum ones are.

Reverse was almost identical between the 3 and 4 blade.

Sometimes I wish there were a "high five" for little motors. Ran a high five on my old bass boat with the little 90 HP motor...that was an awesome prop. Reverse sucked but it wasn't a big deal. You get used to it.

Ideally when switching from 3 blades to 4, you'll want to drop 1" pitch because of the extra blade's drag. That is a rule of thumb. On my 25 I had to go down from a 3 blade 12" to a 4 blade 10" to get the RPM back...but mph only dropped just a tick.

As mentioned, it's also possible to run the engine higher on the transom, so if you can do that, it'll help there too. Watch the water pressure or pee hole though.

 

[New River Rat]

Thanks. TurboT I think we're on the same page here.

 

[New River Rat]

Finally took the old one off to get mono off the hub and saw it was a 10X13. I ordered a 10.5X11 today, 3 blade. I figured a fourth was just one more to bust on ledges.

 

[New River Rat]

I could possibly see an improvement.....

 

[Charger25]

lol :LOL2: yeah I would think so

 

[Johny25]

Well by dropping 2pitches your engine will see a 400rpm or so increase at WOT and much better holeshot. Although that old prop had virtually nothing left for blades so the end result may be hard to tell. If you truly do not run at WOT then going down in pitch is fine as long as you don't forget about it and run your engine way over its recommended RPM range. Even short periods of time over the WOT range is not good for the engine. And if you do not have a baseline RPM from your old prop then you are just shooting in the dark on prop selection. What motor are we talking about here anyway, or did I miss that in the thread somewhere?

Nice prop/skeg guard by the way =D>

 

[New River Rat]

Nice prop/skeg guard by the way =D>

Thanks. It's on a '97 Johnson 25hp that rarely sees WOT.