Boat performance

[Okotokian]

So I have a 17 1/2' Princecraft aluminum fishing boat with a Mercury Optimax 115 horsepower two stroke outboard. It seems to take a bit to get up and on plane. I'm satisfied with the top speed (around 40 mph) but I think I'd like a little better hole shot. I'd be willing to sacrifice a bit of top speed to get it.

Right now I have two propellers I inherited. I did some detective work and found that I have:
- Quicksilver Nemesis 4 blade, 13 inch aluminum prop with 17" pitch (on engine now), and
-Mercury Black Max 3 blade, 13.25 inch aluminum prop with 17" pitch (which I think came with the boat).

Both 17' pitch so I can't imagine there is a whole ton of performance difference, though from what I have read the 4 blade should give me a bit better hole shot and a bit less top end, which is what I want. The 4 blade does have a few dings. Not sure if a file would be helpful.

Any suggestions that would make a noticeable difference or improvement? 17" pitch seems pretty low already. Go to stainless steel? Move to even lower pitch? Both? I do plan to take a look at how far above or below the keel the anti-ventilation plate is. I have read it should ideally be at the keel height and if it isn't performance can suffer.

Thanks in advance.

[ROA]

Just for comparison. On my Lund 17 foot Fisherman I had a Honda 115 with a Honda aluminum 17 pitch 3 blade. 46mph top speed (indicated) with decent hole shot and hitting just under max rpm wide open throttle. .

My motor height was set up so the anticavitation plate was just about showing when up on step and trimmed out correctly.

Tried a 19 pitch Honda 3 blade the boat came with and it was no good. Poor hole shot, touchy to get trim set right and top speed was about the same as 17 pitch.

[iYearn]

If you are looking for hole shot then stainless will improve that. I went stainless on my 20' Merc 3.0 inboard.

Top speed improved by about 5 mph.

But the hole shot improved dramatically.

We also use the boat for skiing, wakeboarding and tubing, as it is a fish/ski Bayliner.

The stainless shows its most improvement on the turns with three large people in the tube. The boat no longer digs.

[Headdamage]

What is your WOT (wide open throttle) rpm?

[Xbolt7mm]

What is your WOT (wide open throttle) rpm?

This

[kcward]

I run a Lund impact 1775 with a 115 merc 4 stroke and put a Vengeance 18p prop on. I get 40-42 with it and she comes out of the hole very quick. I have never ran it with the standard prop, so not sure the difference it makes.
Watch your rpm though, if you are already close to your max rpm I wouldn't go any lower on the pitch, but stainless will definitely help.

Mercury does do some testing that show the results with different boats and props, but it is limited to a select few. Here is a link to that:

https://www.mercurymarine.com/en/ca/engines/outboard/fourstroke/75-115-hp/#specifications

Good luck with your choice!

[CBintheNorth]

Here is a link to a great tool. As others have said, wide open throttle (WOT) RPM is very important.

https://www.mercurymarine.com/en/ca/propellers/selector/?utm_term=en&utm_medium=us+&utm_source=Overlay_IP%3Dca&utm_campaign=Region+Redirection#/step-one
If your main concern is time-to-plane, I would seriously look at one of these...
http://www.stingrayhydrofoil.com/
I installed the 'classic' on my boat because I was too uneducated and too cheap at the time to max out the horse power on my boat when I bought it.
The Hydrofoil definitely gets the boat up quicker (half the time to plane) and gives faster trim-response, which is nice in a light boat that's skipping along.
I would take everything else you read about them with a grain of salt. Didn't speed up my boat, but didn't slow it down either.
One thing you probably already know, but something I notice some people out there don't do, is trim the engine all the way down when taking off. This can double the time to plane.
Just a guess, but I'll bet your 17 pitch prop is going to be at the bottom end of where you should be already for RPMs.
Good luck.

[Okotokian]

What is your WOT (wide open throttle) rpm?

I'll check this weekend. What would that tell me? I am assuming that if top speed RPM is already at recommended max for my boat (I'll check the manual too) that I can't go down in pitch any further as the rpm will become too high?

So stainless prop offers some performance improvements. Great. So should I stay with 4 blade 17" pitch or go even lower in pitch? This is assuming my engine is set t the right height, etc.

[Salmo]

I have a 17.5" Princecraft but have a mercury 115 4S as opposed to your optimax. i have a kicker and 24V trolling motor and typically a fair bit of gear (so a fair bit of additional weight) and performance sounds very similar. I get 40 mph at 6300 rpm WOT with a 13.25 17" pitch Black max. I have tried many aluminum props and the Black Max seems to provide the best combination. I will try stainless to see if I get anything better when I finally ding up the latest Black Max I have on.

[Okotokian]

I have a 17.5" Princecraft but have a mercury 115 4S as opposed to your optimax. i have a kicker and 24V trolling motor and typically a fair bit of gear (so a fair bit of additional weight) and performance sounds very similar. I get 40 mph at 6300 rpm WOT with a 13.25 17" pitch Black max. I have tried many aluminum props and the Black Max seems to provide the best combination. I will try stainless to see if I get anything better when I finally ding up the latest Black Max I have on.

yeah, I have a kicker on the back and electric trolling motor on the front . Sounds like the exact same set up you have and you are still running the original Black Max prop I have as a spare. I can easily live with the performance when it comes to fishing, but I'd like to be able to pull a skier too, and not sure how that will go.

[Salmo]

I am going to guess it will have a lot to do with the skiers ability, my limited experience has taught me that i can get up behind a Mastercraft a lot easier than i can a fish n' ski boat. Those that have years on boards don't seem to sweat the boat that much!! :)

Mine does pull tubers around just fine, i haven't tried a skier yet.

[TROLLER]

Hydrofoil for sure easy to install and not a ton of money and they work.

[ROA]

I'll check this weekend. What would that tell me? I am assuming that if top speed RPM is already at recommended max for my boat (I'll check the manual too) that I can't go down in pitch any further as the rpm will become too high?

So stainless prop offers some performance improvements. Great. So should I stay with 4 blade 17" pitch or go even lower in pitch? This is assuming my engine is set t the right height, etc.

Sometimes stainless props of the same pitch and blade count and diameter will not quite get the same rpm as aluminum because of various factors. Some say to get the same rpm you need to go down 1" of pitch so in your case a 16 pitch. This is not written in stone so take it for what it's worth.

Originally you said your current prop on the boat has some dings? Small dings can make a fair bit of difference. I would run both of your props back to back just to see how they fair against each other. Find the max rpm at the best trim setting to give top speed with each prop also find out the rated rpm for your motor. Post results on here or a boat forum and people will be able to help you out.

[The Reel Deal]

Hydrofoil for sure easy to install and not a ton of money and they work.

you can pick one up from crappy tire and return it if you dont like it, but I bet you'll keep it. These get you on plane quick!

[jim summit]

As mentioned, try the 3 blade, no 2 props preform the same even with the same pitch. A 3 blade will allow faster spool up on the motor with one less blade in the water.

[Okotokian]

you can pick one up from crappy tire and return it if you dont like it, but I bet you'll keep it. These get you on plane quick!

Thanks. How does a hydrofoil differ from trim tabs?

[Okotokian]

Sometimes stainless props of the same pitch and blade count and diameter will not quite get the same rpm as aluminum because of various factors. Some say to get the same rpm you need to go down 1" of pitch so in your case a 16 pitch. This is not written in stone so take it for what it's worth.

Originally you said your current prop on the boat has some dings? Small dings can make a fair bit of difference. I would run both of your props back to back just to see how they fair against each other. Find the max rpm at the best trim setting to give top speed with each prop also find out the rated rpm for your motor. Post results on here or a boat forum and people will be able to help you out.

Thanks. Was thinking of taking a file to the prop to file off the bangs and bends on the edge of the prop.

I used the Mercury Prop Selector ( https://www.mercurymarine.com/en/ca/propellers/selector/?utm_term=en&utm_medium=us+&utm_source=Overlay_IP%3Dca&utm_campaign=Region+Redirection#/step-five ) and it pretty much came up with a bunch of 17" pitch props, whether aluminum or stainless, 3 or 4 blade, for the most appropriate for my boat type and engine.

[Dean2]

If hydrofoils actually works as good as some claim I cannot for the life of me understand why outboard makers don't install that from the get go. IT would cost nothing and supposedly dramatically improve performance. Sorry, but something seems amiss in this equation.

[diamond k]

If hydrofoils actually works as good as some claim I cannot for the life of me understand why outboard makers don't install that from the get go. IT would cost nothing and supposedly dramatically improve performance. Sorry, but something seems amiss in this equation.

I have on on my 17 ft legend with 100hp. Improvement is minimal but will keep it on.

[wellpastcold]

If hydrofoils actually works as good as some claim I cannot for the life of me understand why outboard makers don't install that from the get go. IT would cost nothing and supposedly dramatically improve performance. Sorry, but something seems amiss in this equation.

I also shared your scepticism. I owned a boat that performed extremely well once on plane but was a bear to get out of the hole. I tried a number of different stainless props. I finally tried a stainless hydrofoil from Cabelas. It dramatically improved the excessive bow lift I was getting while trying to get on plane. I don't believe they are the saviour in all situations but if you have tried everything else they can help. Not to mention they are not terribly expensive.

[catnthehat]

If hydrofoils actually works as good as some claim I cannot for the life of me understand why outboard makers don't install that from the get go. IT would cost nothing and supposedly dramatically improve performance. Sorry, but something seems amiss in this equation.

I often wondered the same thing.
My trihull was a bear to get out of the hole and would porpoise like a bugger unless I had a bunch of weight up front.Put on a hydrafoil and three of us could be in the back and it would get up like a boss plane nicely.:)
Cat

[Mangosteen]

A five bladed stainless would get you up faster but with only 115 HP the effect would not be realized.

What is the max HP your rated for and more importantly are you loaded up heavy with fuel, gear, people?

I always go max HP.

17.5 pitch is a workhorse pitch. Use that on my heavy boat for camping. But it's a twenty foot deep Vee with a 225 HP two stroke.

Stainless won't flex as much but you need the horsepower to drive the difference is my opinion.

I added some 12 inch wide by 14 inch long electric polished SS trim tabs and of course that helps get out faster for sure.

Easy to install and wire up. I ordered them out of Florida.

Very happy with them. They are made by Lenco and used offshore quite a bit. The extra size plates are more for a 28 footer but on the 20 ft they work well

Had it out on Fawcett lake a couple days ago.

Lenco makes all kinds of sizes.

They automatically retract when you shut your key off for loading the boat.

[Headdamage]

You will want to know the WOT rpm so that you can see if you have the right pitch prop. You want to have the motor running very close to it's max rpm with the throttle wide open with your normal load in the boat. If your motor has a max of 6000 rpm 5800 to 6000 would be good. Until you know if you are in the right ball park with your current prop all other efforts maybe pointless.

[Okotokian]

You will want to know the WOT rpm so that you can see if you have the right pitch prop. You want to have the motor running very close to it's max rpm with the throttle wide open with your normal load in the boat. If your motor has a max of 6000 rpm 5800 to 6000 would be good. Until you know if you are in the right ball park with your current prop all other efforts maybe pointless.

Point taken. I will check next time I've got her out on the water. Thanks.