Prop Size

[Southern Hunter]

Ok for starters I know there is no “correct answer” to this question, but I’m just looking for some input and possible first hand experience with what I’m asking.

I just acquired a brand new Weldbilt 1442 with a Mercury 15 4 stroke on the back. The rig came stock with a 9p aluminum prop and I’m wanting to upgrade to a Stainless one and am thinking of going to either an 11 or 12 pitch. Average load for the boat will be roughly 450lbs. If I were able to run multiple sizes before I purchased one I would, but trying to get it right the first time so the $300 purchase is a one time thing. Does anyone have a similar setup and any first hand experience or input they’d like to share?

[Tim Kelly]

I have a 12ft tin boat, decked out, so relatively heavy, with a suzuki 20 on it. I run a 9p most of the time. If I'm on my own I can run a 10 and gain a couple of MPH. I tried a stainless prop but couldn't make it work. I think it lifted the hull too much for the engine height so cavitated once on plane and I can't drop the motor as I've built the transom up. 1" of pitch makes a huge difference on these boats with small motors. I'd try a 10 and 11 in aluminium first if I were you, but if you're not hitting the rev limiter with the 9 it might well be about the right size.

[alanhore]

First thing to do is see what rpm your motor runs at wide open throttle on your current prop. Tinytach is what I used on mine. If you are not getting to max rpms it wont do any good to go bigger in pitch. If you are over you max rpms then you can got up in pitch.

[Southern Hunter]

I appreciate both responses, that’s what I need to do….go run it and go from there. I was going off a buddies experience with the exact same setup and to his best recollection he ran an 11p.

[CincyGus]

SH, Alanhore has you on the right path. Load the boat how you usually fish it. Go see what your RPM is at max, topped out speed on smooth water. See how that matches up with the engines rated max RPM's. Generally the RPM's drop 150-200rpms for every pitch you go up. They drop by similar amounts for every pitch you go down. 4 Blade props help stay hooked up better in turns, improve hole shot and time to max speed and help handling but may cost you an extra 50-100rpms down. Stick with aluminum unless you're propping a 150hp or larger engine unless you have specific need for it.

[Stratos81]

Just curious why do you want a SS prop?

[Southern Hunter]

The reason for the SS prop is the likelihood of hitting stumps, logs, other debris, etc. SS props tend to be MUCH more resilient than aluminum props.

[willwork4fish]

more resilient for the prop, less resilient for your lower unit. I'd rather have damage to my prop than prop shaft. I've got a Crestliner 1650 with a Yammie 40 and run shallow a lot. Have gone through a few props but never a LU issue. Little aluminum props are cheap.

[Tim Kelly]

Likewise

[Southern Hunter]

Just an update….

Finally had a chance to run the boat, I went out on a limb due to the advice of a good friend and I’m overall fairly satisfied with the results.

I went with an 11p Power Tech SS Prop. With me and my son, roughly 300lbs total weight, the boat ran up to 25mph with zero porpoising, good handling, and very good hole shot. If any, the only thing I’m not 100% on is the fact that I could only turn up roughly 5200rpms.

May end up trying a 10p eventually but for now, I’m happy with where we’re at!

[tcesni]

Just an update….

Finally had a chance to run the boat, I went out on a limb due to the advice of a good friend and I’m overall fairly satisfied with the results.

I went with an 11p Power Tech SS Prop. With me and my son, roughly 300lbs total weight, the boat ran up to 25mph with zero porpoising, good handling, and very good hole shot. If any, the only thing I’m not 100% on is the fact that I could only turn up roughly 5200rpms.

May end up trying a 10p eventually but for now, I’m happy with where we’re at!

What is the maximum rpm for your motor? Just curious.

[Southern Hunter]

What is the maximum rpm for your motor? Just curious.

Max RPM’s for my engine show 5000-6000.

[Tim Kelly]

Good job.

[doctorxring]

more resilient for the prop, less resilient for your lower unit. I'd rather have damage to my prop than prop shaft. I've got a Crestliner 1650 with a Yammie 40 and run shallow a lot. Have gone through a few props but never a LU issue. Little aluminum props are cheap.

Have you considered a Piranha propeller ? I've used them on my aluminum boats for decades. They are great for "troubled waters" like you are looking at. It's a very durable composite with replaceable blades. You hit something and trash a blade it's $20 to replace it. Piranha will let you try the pitch of your choice and let you exchange the blades if you need to go up or down in pitch.

Call them on the phone. They will help you. piranhapropellers.com

[FrancoCialone]

Just an update….

Finally had a chance to run the boat, I went out on a limb due to the advice of a good friend and I’m overall fairly satisfied with the results.

I went with an 11p Power Tech SS Prop. With me and my son, roughly 300lbs total weight, the boat ran up to 25mph with zero porpoising, good handling, and very good hole shot. If any, the only thing I’m not 100% on is the fact that I could only turn up roughly 5200rpms.

May end up trying a 10p eventually but for now, I’m happy with where we’re at!

Sounds like the 10p might be the prop for you, I've always read that your engine should be reving at the upper end of rev range at wot with a "normal" load, this will give you good holeshot and top speed, but you could prop for better holeshot/heavier load or for top speed.