Prop Pitch Recommendations - need help

[AC2717]

Hi Guys
Looking for some advice. I have a 2007 Lowe AN140s 14 foot Lowe Fishing model aluminum boat with a 207 25hp mercury EFI 4 stroke on the back non Bigfoot and gearing is 1.92x1 and max RPM is 6000 (serial 0R181035). The boat weighs about 601lbs without the motor which is 148lbs and the safety plaque says 5 people or 550lbs for gear and people.

I am about 205lbs, battery is 65lbs 6 gallon fuel jug, fishing gear, and then my fishing partner (my daughter) is 125 lbs. so with the motor we are basically capacity. When my daughter takes the boat out lets just say it moves a little faster without me on it and planes a little better, but I do not think it gets out of the water as much as it should. When just me on the boat i have to stand to get it to plane out somewhat and move a little faster and stay there, and when I turn slows down and bow up again, when both on the boat i have to sit up the bow but we are still throwing a wake more than it should
all of the above is at WOT. In all conditions (except with just my daughter on the boat, and even then in watching it does seem like still could see a little help), it just seems like it should be a little more out of the water and then obviously move quicker than it is. add this one: don't even think about touching the power trim, it will slow down.. The engine is in perfect running condition and has been checked out by a tech that teaches on Mercurys, I had to replace the fuel system a little while back due to ethanol and the lower end was serviced over the winter (needed to be when I purchased it). I wasn't unhappy with the performance when I put it on the water but now I feel like it is under performing for the size of the boat and engine, but know its a lot of weight. But I also see larger boats on a 25hp and same size whalers and they seem to get a better performance. I am looking for more speed and getting the hull up

The engine and set up from boat maker and mercury calls for a 9 inch pitch to and 11 pitch but we all know they are guidelines for the most part and it has to be application specific. It is a 10 spline prop shaft. Currently there is a 9.9 x 9 pitch on the motor (brand new) and I have put a foil on (SE200) to help it get up out of the water, it helped a little but it seems like the motor is working hard and the boat itself is weighing it down so to speak.
I have pulled as much weight as I can out of the boat already, understand more pitch is more speed but slower hole shot. So do i increase pitch and diameter as well??? How do I test everything out without buying numerous props and being stuck with them?

I have a 10 x 11pitch stainless prop to put on there, but mechanic advised to take it off due to the weight of the prop and the size of the motor and the lower end and shaft taking the extra weight on?? Also mechanic ran without me present a 10 pitch prop and he went with the 9 stating the boat was very heavy for that motor and would have done a 8 pitch if had it on hand to try.

I also have a beat up quicksilver 4 blade 9.3x11 prop that was on it before the lower end needed service (before I owned) that I was going to try out but was worried with the blade ends being chewed up might not give me a good test

motor placement on hull is correct to manufacture specs for motor and hull, no leaks balance/floatation foam is dry and bilge is dry. Boat and motor was sold together as a package.

Speed test done with phone speedometer gps app and just daughter on boat Max speeds at WOT solid 18mph in one direction 3 times same distance
and 16.5/17 sometimes hitting 18 in the other direction 3 times same distance with that gearing should be about 24mph at 6000 rpm (I do not have a tach on the boat)

Also does anyone have this same boat and set up and has experience with it? help me out here. thank you

 

[DaleH]

... did you ever try this? It is a 'sticky post' in the Motors Forum: https://forum.tinboats.net/viewtopic.php?f=4&t=37433

FWIW it has been 'spot on' for every hull I've rigged; just did another for a friend the other day.

If you do need a new prop, get their 'Hustler' pressed aluminum props, even the 4-blade model, unreal hole shot and load carrying capacity.

 

[AC2717]

I plugged it in, waiting for them to respond, system did not pull. But thank you

one thing i thought was weird that some peopleand mechanic are telling me to go to a 8 ptich? merc says 11 and mechanic say ran best with a 9? (again he only ran a 10 and a 9

 

[DaleH]

I plugged it in, waiting for them to respond, system did not pull. But thank you

If they don't have your specific hull, I find using one by another make that is as close as possible in shape, weight and beam, from another boat make, works really well too!

But in a hurry, call (904) 900-7739 and ask for Phil and please tell him you heard about them on TinBoats or send email to [email protected]

One thing i thought was weird that some people and mechanic are telling me to go to a 8 pitch? Merc says 11 and mechanic say ran best with a 9? (again he only ran a 10 and a 9

In 40+ years of rigging boats I have yet to see a hull wear the exact prop that the OB maker recommended ... as my 2 biggest boating pet peeves are the wrong pitch prop installed and OBs mounted too deep!

 

[k13west]

A tachometer would be a big help. Look into Tiny Tach models. 40 bucks and easy to set up. If the motor feels bogged down and is slow to plane it's likely you'll want a lower pitch prop. I'd guess the 8 inch pitch would be perfect. You'll lose a mph or two at WOT but you'll be much happier with the acceleration and the motor will be happier to not be loaded so hard.

I bought a 15' Smokercraft Lodge a year ago with a 25 Yamaha. I run it for 3 months with a steel frame duck blind and the rest of the year without. I own 9, 10, and 11 pitch props that I'll swap depending on the load. All of the calculators said that 9 pitch was too low, but I tried it anyway and it is the answer when I have a duck blind, decoys, a dog, extra clothes, shotguns, ammo and two men in the boat. It runs WOT at 5500rpm and hits 20mph

If I keep that 9 pitch on without the duck blind and gear and just go fishing solo I'll hit the Rev limiter on the motor at 6300rpm. Put the 11 pitch on and it runs at 5850rpm and 24mph.

Sent from my moto g(7) power using Tapatalk

 

[AC2717]

Thank you DaleH and thank you K13west
i will give them the day to respond. I will be getting a tach on it this weekend, hopefully sooner rather than later, in doing my slip calculation I appear to be in the mid to low 30s which is not good on the current 9 ptich (if I am hitting the 6000rpm). I plan on trying to find a 8 pitch to test along with the 11s i already have (stainless and 4 blade quicksilver) against what I already know on the 9 pitch. hoping for clear water on the test day as that was how it was on the 9 pitch yesterday

i guess with this size motor it is trail an error? i was always under the belief that smaller the pitch the better hole shot but lower speed which is why I am having a hard time believing the 8 pitch would be better?? Prop wizard said they did not have exact application and will get back to me with exact, but the page was recommending 11 pitch even possibly a 13 pitch.

Depending who you come into contact with and online its either 8 through 13 pitch now

 

[DaleH]

i guess with this size motor it is trail an error?

Prop testing on any boat is a 'try & test' affair! Took me 3 tries to get the BEST prop on my current offshore rig and am glad I went w/ Turning Point, as I am using big 15" diameter, 4-blade, espen$ive SS props ... but one can swap them out with T-P for only a $35 exchange fee.

I got setup to where I'm only 100 RPMs off max on clean running bottom, all gear normally carried and me aboard with ~ 1/3 tank of fuel. As is, boats only get HEAVIER as the season progresses ... more gear, more people, more gas, more growth on the hull (my big boat is moored), and hotter temps, which makes the air thinner.

 

[AC2717]

Prop Wizard came back with a 11 pitch. In speaking with ken at Prop gods and like others have stated, I have to get to the motor and see where the cavitation plate lines up with the keel to see if I need to move the motor up, which in looking in pictures I have, i am not with the boat now, I might have to

 

[k13west]

i guess with this size motor it is trail an error? i was always under the belief that smaller the pitch the better hole shot but lower speed which is why I am having a hard time believing the 8 pitch would be better?? Prop wizard said they did not have exact application and will get back to me with exact, but the page was recommending 11 pitch even possibly a 13 pitch.

Depending who you come into contact with and online its either 8 through 13 pitch now

Isn't your problem a poor hole shot/slow to plane? If so then go to a lower pitch prop. You'll lose a bit of top end speed, but the boat will pop up on plane and your motor won't need to work so hard. I tried all the online pitch calculators I could find but I load my boat heavy and no calculator gave me a suggestion lower than 10" pitch. I went to a 9" anyway and it was perfect. I know it's not cheap to test buy different props but I'm very glad I did.

Sent from my moto g(7) power using Tapatalk

 

[AC2717]

The experiments will begin Friday lol. In having looked at the motor placement further through suggestions, the anti- ventilation plate seems to be 2 inches or so under the keel line of the boat, which is a big no no. Old owner i know took the motor off at one point and probably installed it back too low.

So step one is to move the engine up, which I have room on the bracket to adjust. Then I will by doing runs with the props to see performance results. with a tach tester.

 

[Midwesterner]

Get the engine at the right height, I have a 20 hp four stroke running a 9.25x10 and it will run 24 mph at about 750 lbs and fully loaded at 950 lbs 20 mph @5,800 RPM. The 20 hp is a dog, the 25 should be kiillng it. I know my redline is 6,100 and the power band hits about 5,500. This is on a 14' deep v with a utility hull.

Local shop told me I was wasting time chasing performance on the 20 hp since it's not there. They said stainless props on the lower hp engines is a no no due to weight. Also said every pitch change will change the rpms by 200-400.

I run this tach, just wraps around the coil, there are two versions and one is built for outboards and down the page.

https://tinytach.com/gasoline-tinytach

 

[ktoelke54]

Get the engine at the right height, I have a 20 hp four stroke running a 9.25x10 and it will run 24 mph at about 750 lbs and fully loaded at 950 lbs 20 mph @5,800 RPM. The 20 hp is a dog, the 25 should be kiillng it. I know my redline is 6,100 and the power band hits about 5,500. This is on a 14' deep v with a utility hull.

Local shop told me I was wasting time chasing performance on the 20 hp since it's not there. They said stainless props on the lower hp engines is a no no due to weight. Also said every pitch change will change the rpms by 200-400.

I run this tach, just wraps around the coil, there are two versions and one is built for outboards and down the page.

https://tinytach.com/gasoline-tinytach

I have a Lowe 1467 utility with a 20 hp efi Tohatsu. The Performance is pretty close to what your posting. I looked up the boat the OP states he has and it looks like a fully decked version of my 1467 hull. It weighs 300+ pounds more than my boat! If I were to add two people, trolling motor, battery etc, and then throw a 300 pounder on the middle seat. My boat would perform as the op described. That’s a lot of weight for a relatively small plaining surface. I occasionally carry a third adult in my boat (no where near 300#) I go from a ten to a nine pitch and and it still planes but feels like it’s maxed out.

My total weight with two big guys is right at the coast guard sticker limit—just shy of 1K. The third guy puts me over, and the performance drops rapidly.

Having said all that I think that with a tach and the right prop there’s lots of room for improvement with that setup.

My experience with the small hp props is that dropping one pitch makes a large difference in rpm.


Sent from my iPhone using Tapatalk

 

[AC2717]

Update from the weekend:
motor was almost 3 inches below where it should have been. without it being on the trailer (on a lift in the water), a friend of mine and I were able to lift the motor up almost as far as it will go. It is not where it should be 100% for location but what a difference. I believe I can get it up one more spot without drilling holes (which I wont do), but we were a loss to get it to the next step (needed a third person) also might not have the ability to do that given the holes, and where the top clamp brackets are on the hull themselves), but I think it can be done. Best prop on there was the 9.9x9 3 blade, the 11 pitches were terrible performance.

Nest step is to find a 8 pitch, and see what that does. also was toying with (if cant get the motor any higher) to remove the foil to create less drag if cannot get it to above the water line before throttling up.

Thoughts??

 

[Midwesterner]

Need more vertical?

https://www.cabelas.com/product/T-H-MARINE-SUPPLIES-MINI-JACKER-JACK-PLT/3017887.uts

 

[turbotodd]

A tachometer is not simply a tool to have when adjusting the prop.

A tachometer is absolutely paramount! You simply can NOT tune the prop and motor setup without a tach, period.

You need a tach.
You need a tach.
you need a tach.

Shall I repeat?

LOL! Seriously, without it you're peeing into the wind.

With the tach installed, you will run across the water and watch the max rpm. Once you know that, you can adjust from there. More pitch=less max rpm. Less pitch=more max rpm.

The 3 cyl tohatsu (merc) 4 stroke isn't known for speed; they are torqueless smooth and quiet running dogs. I have run and tuned several and they impress me with the quiet/smooth operation but that is about all they impress me with. The foot is 1.92. Most of the other 25hp brands are 2.08+. The final gear ratio (foot aka lower unit) has a lot to do with how quickly the engine will spin up from idle. The higher the number, the faster it will achieve RPM and vise versa. With the merc/tohatsu (same motor) being 1.92 it's not going to be real responsive from idle speed as you advance the throttle in comparison, AND it can't turn a "normal" pitch prop (normal being 11-12-13" pitch that most other 25hp motors can run) so you have to drop the pitch a little to make up for the lower gear ratio. Where a Suzuki might run a 12" (2.09), a merc/tohatsu might only be able to turn a 10" because of the 1.92 foot.

yes if the foil is below the waterline, it's going to drag the ever living poo out of the entire rig. They work, but only if the motor is set up correctly, in other words when the foil is completely out of the water when the boat is on plane at speed and trimmed out. Without PT&T it's harder to get that perfect setup which is why I generally do not recommend foils on a smaller boat, particularly manual tilt jon boat setup.

most guys run their motors too deep and a lot of that is because they are set up from the dealer and never touched. Dealers always set them low for a reason; it's impossible to starve the water pump if they're deep. If they set them high and the operator starves the pump & destroys the engine, the dealer is easily held responsible and powerheads aren't cheap, espeically when you get into the inline 4 and v6 stuff and then dual, triple, quad engines in some cases.

 

[Flygaff]

I agree with the tach issue. You know how the engine performs by what the tach tells you. My 20 hp Suzuki wants to run at 6300 rpm. Over that and you hit the limiters. Under that and you need to change the prop pitch. It’s a balancing act

 

[Duro]

Get the engine at the right height, I have a 20 hp four stroke running a 9.25x10 and it will run 24 mph at about 750 lbs and fully loaded at 950 lbs 20 mph @5,800 RPM. The 20 hp is a dog, the 25 should be kiillng it. I know my redline is 6,100 and the power band hits about 5,500. This is on a 14' deep v with a utility hull.

Local shop told me I was wasting time chasing performance on the 20 hp since it's not there. They said stainless props on the lower hp engines is a no no due to weight. Also said every pitch change will change the rpms by 200-400.

I run this tach, just wraps around the coil, there are two versions and one is built for outboards and down the page.

https://tinytach.com/gasoline-tinytach

Yes, i agree. Definitely check outboard height & get a tach hooked up first before buying another prop.

 

[Bruce Benson]

Hi Guys
Looking for some advice. I have a 2007 Lowe AN140s 14 foot Lowe Fishing model aluminum boat with a 207 25hp mercury EFI 4 stroke on the back non Bigfoot and gearing is 1.92x1 and max RPM is 6000 (serial 0R181035). The boat weighs about 601lbs without the motor which is 148lbs and the safety plaque says 5 people or 550lbs for gear and people.

I am about 205lbs, battery is 65lbs 6 gallon fuel jug, fishing gear, and then my fishing partner (my daughter) is 125 lbs. so with the motor we are basically capacity. When my daughter takes the boat out lets just say it moves a little faster without me on it and planes a little better, but I do not think it gets out of the water as much as it should. When just me on the boat i have to stand to get it to plane out somewhat and move a little faster and stay there, and when I turn slows down and bow up again, when both on the boat i have to sit up the bow but we are still throwing a wake more than it should
all of the above is at WOT. In all conditions (except with just my daughter on the boat, and even then in watching it does seem like still could see a little help), it just seems like it should be a little more out of the water and then obviously move quicker than it is. add this one: don't even think about touching the power trim, it will slow down.. The engine is in perfect running condition and has been checked out by a tech that teaches on Mercurys, I had to replace the fuel system a little while back due to ethanol and the lower end was serviced over the winter (needed to be when I purchased it). I wasn't unhappy with the performance when I put it on the water but now I feel like it is under performing for the size of the boat and engine, but know its a lot of weight. But I also see larger boats on a 25hp and same size whalers and they seem to get a better performance. I am looking for more speed and getting the hull up

The engine and set up from boat maker and mercury calls for a 9 inch pitch to and 11 pitch but we all know they are guidelines for the most part and it has to be application specific. It is a 10 spline prop shaft. Currently there is a 9.9 x 9 pitch on the motor (brand new) and I have put a foil on (SE200) to help it get up out of the water, it helped a little but it seems like the motor is working hard and the boat itself is weighing it down so to speak.
I have pulled as much weight as I can out of the boat already, understand more pitch is more speed but slower hole shot. So do i increase pitch and diameter as well??? How do I test everything out without buying numerous props and being stuck with them?

I have a 10 x 11pitch stainless prop to put on there, but mechanic advised to take it off due to the weight of the prop and the size of the motor and the lower end and shaft taking the extra weight on?? Also mechanic ran without me present a 10 pitch prop and he went with the 9 stating the boat was very heavy for that motor and would have done a 8 pitch if had it on hand to try.

I also have a beat up quicksilver 4 blade 9.3x11 prop that was on it before the lower end needed service (before I owned) that I was going to try out but was worried with the blade ends being chewed up might not give me a good test

motor placement on hull is correct to manufacture specs for motor and hull, no leaks balance/floatation foam is dry and bilge is dry. Boat and motor was sold together as a package.

Speed test done with phone speedometer gps app and just daughter on boat Max speeds at WOT solid 18mph in one direction 3 times same distance
and 16.5/17 sometimes hitting 18 in the other direction 3 times same distance with that gearing should be about 24mph at 6000 rpm (I do not have a tach on the boat)

Also does anyone have this same boat and set up and has experience with it? help me out here. thank you

 

[Bruce Benson]

Solas 10.8 10p should make you very happy. I replaced my 10.3 12p Wot 4500 rpm with the 10p wot now 5350 rpm topend increase from 21 to 23 mph. The engine runs so much nicer . My trapper topper 15 stick steer 2018 with 1989 25hp evinrude. Engine power range is fo 4500 to 5500rpm.

 

[airshot]

What does your tach read at wot ? Without a tach, your guessing.