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1996 Force 75hp propeller replacement for 25' pontoon?? DIAMETER/PITCH??

Pretty much a complete rebuild of a 1996 Brunswick 25' pontoon boat and down to
the propeller replacement for our 1996 Force 75hp outboard motor. I think the prop now
is the OE from 1996. The numbers stamped on the prop are:
OE Quick Silver 48 97868 A10 9P
I'm assuming this is a "9 PITCH" prop but that is all I can decipher from this number being the
novice I am
. Anyone help with what the numbers mean? Is the DIAMETER in this stamped #?

I would like to replace the propeller with one that offers faster top speed. I realize we will lose
some torque (faster out of the water) with the higher PITCH (ie: 10p, 11p, 12p, etc) but willing
to sacrifice the out of water faster for top end speed as we do not pull tubers etc.

My questions are:
#1: Which PITCH would be the most efficient for the 1996 FORCE 75hp to get the better top speed
and not damage the engine in making the change?
#2: Would installing a new propeller that has "cupped" blades offer any better efficiencies
for top end speed?
#3: Would it be best to go back with a "Quick Silver" propeller or shop the after-market products
which often provide newer and better technologies?
#4: Any idea specifically which DIAMETER/PITCH propeller would be the best for my situation?

I know the answer to my real question. Yes, it would be best to ditch the '96 FORCE and install a brand new 115hp newer 2-stroke design (not real interested in the 4-strokes for this salt water environment and the extra weight it would add to the 25' pontoon) but my goal is to run the 75hp till it dies. At this point, the way it's running is it might outlive me!!! ha ha!

Thanks for any suggestions from you experts with any experience in propeller upgrades.
 
Looks like a stainless prop might be a vengeance series, it is 12 1/4" diameter 9" pitch. That prop is probably the best prop you can be running for your application. I don't know if you can get better.
The quicksilver props are some of the best out there.
I wouldn't ditch the force they are good motors that take a lot of undeserved heat.
 
Usually the prop/motor combo that came with the boat is the best one for speed on a pontoon.
You'll need to know what the rpm's at wide open are???

Your motor should run at 5200 +/-
Load on a pontoon can affect the speed a LOT!!!

If you go to a stainless of the same pitch you'll probably slow down.

Measure the diameter, figure out the rpm's at wide open(remember the load).
Then post the results here or contact Michigan Propeller.
MP will know what you need to go faster.

Faster: Bought a new boat in 88 it came with twin 85hp and was 21ft.
Not a speeder at all!!
I wanted MORE!!! so I changed the 17p to a 19p for MORE!!!

I got more about 2-3mph more and the fuel consumption went up about 20% MORE!!

The only way to go faster is a bigger motor.
The 96 Force is all Mercury with a Force block.
You can change to almost any Mercury.
Just make sure you get the rite size shaft.
 
Thanks for the help!

I held a tape up to the prop and it looks to be 11-12" diameter with the 9P stamped.
I'm pretty sure the current prop is stainless and worn.

Even if I have to go to an aluminum for faster top end speed I'm ok with that, I think.

My WOT is about 4700rpm with 5-6 people on board. WOT last summer was ~5300-5400rpm.
I did put on a new binnacle 1st of last summer so I might not have my throttle cable adjusted exactly perfect.
But it seems I have lost about 5000rpm WOT and thinking it might be time to replace the prop.

Thoughts?

THANKS!!!
 
You mean 500 not 5000???
Pics always help.
Do a compression and spark test.

A stainless doesn't usually wear like an alum. one does.
The rpm's will go up if the prop edges wear off.

My dad had an old Johnson with an alum prop.
He used it for 20 years and complained about the performance.
He measured the prop and it had lost about 1/4 in. in diameter over time.
He installed a new one and the performance returned.
It's amazing over 20 years he never hit anything or found the bottom.

A normal test is 1-2 people with CG equipment and 1/2 tank of fuel.

If you have 5-6 people you probably have a dog or 2 and coolers full of ice and beer and who know what else.
Unload a bit and see if the rpm's come up??

Or if that the way your gonna run all the time?? Then reprop.
To bring up the rpm's lower the pitch say from a 19 to a 17
 
Well, I chose to go with the solas 12 pitch. The description says
for pontoon boats. Hope the jump from a 9p to the 12p works
ok for this 1996 75hp force. It has been running pretty good the last 2 weeks.
Knock on wood~

Thanks for your advice.

[h=1]Solas New Saturn 3-Blade Prop, Pressed Rubber Hub / SS, 11.4 dia x 12, RH[/h]
 
Let us know how the 12p works.
Usually on the bigger props the ss to alum is about 2 pitches.
But once you get to the smaller ones it's more like 1 to 1 and 1/2 pitch.
So a 12p Alum. is more like a 10-11p ss.
 
This will be interesting. The quicksilver prop we currently use is a Stainless Steel 9P ~12"diameter 3-blade pressed rubber hub (been re-pressed by Bull's Prop Shop once about 6 yrs ago) and is the original that came on my 1996 75hp FORCE 2 stroke.
The replacement will be the SOLAS Saturn Stainless Steel 3-blade pressed rubber hub/ 12P 11.4 diameter.

Hope the ole engine responds nicely to this changeover.

THANKS! Will let you know how it goes~
 
PROPELLERS 101





Scroll down or click a link below to learn about each topic:

Choosing the Right Propeller
To some, choosing the right boat propeller can seem like a job for a marine service center. Anything that has to do with the backend of the boat can be a scary thing. Despite popular belief, choosing the correct propeller for a particular boat and motor is actually a fairly simple thing to do, once you understand what a propeller really is.

First think of propeller as a gear, whether it be on a car or even a bicycle. The lower the gear, faster hole shot, more power, but revolutions are much faster so at a point you can only turn that gear so fast until you over rev the engine (or you legs). Now think of your car stuck in only 5th or 6th gear, very slow out of the hole, little torque, but eventually it will catch up with itself so you can cruise to a good speed.

The same basic concept applies to propellers, except with a prop you are committed to only one ?gear". So what to do now? Find the prop size that will give the best overall performance. Sound difficult? It's really not.

Your engine has a recommended wide open throttle rpm range. Let take an example of an18' boat with a 125 hp engine with a rpm range of 4500-5500. In most cases you purchase a boat with some sort of propeller on it. Let's say this motor has a 21 pitch prop on it and at wide open throttle under a normal boat load, the engine turns 4900 rpms. Well it's in the range so it's the correct prop, right? Well yes and no. For the health and longevity of the engine it's okay, but for overall performance, you want to run a propeller near the top of the range. Well how do you change the size to get that?

Remember this rule of thumb: For every 2" of propeller pitch, rpm's will change approximately 400 rpm's. As you drop in pitch, rpm's increase, and as you go up in pitch, rpm's decrease. So if we want to raise our rpm's we should choose a lower pitch prop. Following the rule, going down to a 19 pitch should raise our rpm's to about 5300. That would help the hole shot and also gain us some more speed.

As you follow the rule of thumb, remember that sometimes rules are meant to be broken. This is not an iron clad rule, sometimes varying 2" of pitch will only change rpm's by 200. Switching prop brands or manufacturer, it can sometimes throw off the rule too.

At this point the most important thing to understand is that less pitch means more rpm's, more pitch means less rpms. For your boat to perform at its peak, you need to run at the upper end of your engine's recommended rpm range. That's it. Once you're there and still want more speed, handling, lift, etc, that's when choosing the right propeller brand comes into play.

Here's a simple adjustment you can make to improvement performance under varying boatloads: If you normally run with one other person on board, use that boatload as your measurement when determining your wide open throttle rpm's. But if you sometimes load the boat with 2-5 more people or try pulling a water skier or tube, get another prop 2" of pitch lower than your normal prop. It will compensate for added weight and drag and make a huge improvement on performance in these circumstances. But remember to keep an eye on you rpm's when running a lower pitch for these circumstances.

Most props have the size marked somewhere on the prop, either on the barrel, on the blades, or in the front or back of the propeller. Use that pitch that you're currently running as your starting point. If it's already running correctly then that pitch is your pitch.
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Hub Systems
Most propeller brands now require propellers to use a transferable/removable hub system that you can do yourself. This means once you buy a propeller and hub system combination you can buy just a replacement prop or different pitch prop with out the hub, at a lower cost. That saves you money. That is the whole idea for these hub systems .There are different props and hubs made for different engine brands and engine sizes.
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Aluminum vs. Stainless Steel
The decision between purchasing an aluminum or stainless steel propeller can be difficult. However if you fully understand the differences between them, your decision can be much easier.

The most common understanding of the difference is that stainless steel propellers perform better than aluminum propellers. This is only half true. Material (Stainless vs Aluminum) only accounts for approximately 10% of the actual performance of the propeller. The other 90% of performance is in the blade design.

Well designed aluminum propellers will out perform an average stainless steel propeller. So it's important to research a propeller's performance before your purchase. It is also important to try different pitches and brands to get your boat dialed in to the best possible propeller.
The advantage of a stainless steel propeller over aluminum is durability. Stainless props can withstand more of the damage caused by small rocks, sand, or other loose objects in the water.

However, the disadvantage to a stainless propeller is that there is ?minimal give" to the blades, so if you hit an object hard enough, there is a possibility of causing major damage to your lower unit is increased greatly. With aluminum props, the blades will most likely sacrifice themselves before any damage is caused to your lower unit.

If you run in deep or familiar waters, or in salt/brackish water, a stainless steel propeller can be a good choice. But it is important to always carry a spare propeller on board, and a spare aluminum is an inexpensive choice.
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Three blade and four blade propellers
Three blade props are generally the all purpose propeller of choice. They will get your boat up on plane well with good pulling power and give a faster top speed than a four blade propeller.
Four blade propellers are made basically for a little quicker time to plane, more power for towing tubers and skiers, less cavitation problems in tight turns and they work well on larger boats that are slow to plane. Their top end speed is a little slower than a three blade prop and they cost more.
Both three and four blade props are available in aluminum and stainless steel.
For mid-size and larger engines only.
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Why not run a damaged propeller?
Continuing to use a damaged propeller can cause damage to the gearcase and ultimately the power head of your motor. When a propeller has sustained damage, it will not spin true, thus creating excessive vibrations that will transfer all the way into your motor.

A damaged propeller will also not perform as well as a new propeller because the damaged parts of the blade can degrade hydrodynamic efficiency.​


 
What is pitch?
Propeller pitch is the theoretical forward movement of a propeller for one revolution, assuming that there is no prop slip. For example, a 21 pitch propeller will theoretically move 21 inches for every revolution. Propeller slip occurs with every propeller, but the amount of slip varies depending on propeller design. More aggressively and efficiently designed propellers will slip less.

When selecting a propeller pitch for your boat, it is important that the propeller runs at the upper end of your engines wide-open-throttle RPM range. If you want your RPM's to increase, go down in pitch. To decrease RPM's, go up in pitch. As a general guide, for every 2" of pitch, RPM's will change approximately 400 RPM's.

For water sports or extra people on board, you should generally drop 2" of pitch to help compensate for the added weight and drag on your boat. It makes a noticeable difference in your boat's hole shot, fuel efficiency, RPM's, and overall performance. You should ALWAYS carry a spare propeller on board, and if you're into water sports or occasionally load the boat with extra people, a spare prop with a lesser pitch is a good idea. When thinking a propeller pitch, compare it to a gear on car - lower gear, higher RPM's.

The same pitch from different manufacturers will run slightly different RPM's due to a difference in blade design. Speed differences among the same pitch from various manufacturers will vary even more. For example a 17 pitch from one brand could run up to 7 mph faster than a 17 pitch from another brand.

Pitch is the 2nd two digits that are listed in a propeller item description (14-1/4 x 19, 19 is the pitch, 14-1/4 is the diameter)

What is diameter?
Propeller diameter is distance across the imaginary circle that a spinning propeller makes. It can be easily determined by measuring the distance from the center of the hub to the tip of one of the blades and multiplying that number by 2.

Diameters between different propeller manufacturers may vary slightly. For example for a V6 outboard application, Turning Point uses a 14-1/4" diameter where a different manufacturer may use a 14-1/2" diameter. This small variance does not affect your performance as much as the pitch and overall design. However, larger diameter propellers - 15" or 16" diameter - are designed for larger boat applications - 23 ft +, and are not ideal for 15" - 22" foot run-a-bouts. These larger boats need more blade area to push more water.
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What is rake?
Propeller rake is the degree that a propeller blade is angled in relation to the hub. Props with higher rake typically have better speeds and greater lift. The better performing propellers typically have between 20 - 30 degree rake angles.
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What is cupping?
Propeller cupping is the curved lip at the trailing edge and/or tip of the propeller. Cupping helps the propeller to get a better grip in the water for better holding at higher trim and on turns. Cupping also increases the efficiency of a propeller and can result in higher top end speeds when properly designed.
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What are vent holes?
Vent holes are holes behind each blade designed to aid in the hole shot of a propeller. When accelerating from neutral, these holes allow some exhaust bubbles to flow through and flood the blades. The prop is then spinning through more turbulent water, thus gaining RPM's and speed more quickly. After approximately 1000 RPM's, the exhaust flows rapidly enough that is will bypass the holes and flow through the hub, eliminating any further slippage from the holes.

This performance feature can only be found in stainless steel propellers. However Turning Point is the only one to offer this feature in aluminum propellers as well.​
 
A 75hp will never pop it up out of the hole your pushing a big barge. Your best bet is to achieve proper WOT rpms for the extended life of the motor and just live with the speed it attains. Michigan wheel makes some good pontoon props 14w11p- 14w12p and 14w13p with the extra cup my guess is the 11p would be best for a loaded boat?
 
The SOLAS description for the "New Saturn" prop the marketing material states this prop works well for pontoons so I think I'm good as far as which prop I decided upon. The prop seems to be working well although I really cannot tell much difference. The WOT is now about 4200 RPMS a drop of about 500rpms which is expected because my pitch went from 9P to 12P. Is it realistic to expect to have the trottle adjusted to reach WOT of 5200RPMS and then I back off the throttle to about 4600rpms for cruising? I just do not feel the engine is performing at it's potential. Am I delusional? ha ha!
But I think I need to adjust the arm that controls the throttle (throttle linkage) https://www.marineengine.com/parts/...96/0e138600-thru-0e202999/towershaft-assembly
to the correct high end pf the RPM range for the 75hp 1996 Force engine---which is about 5400 rpms?
New Saturn
- All-around performance
- Good acceleration
- Large ear blade design
Stainless
3 Blade Propeller - Thru-Hub Exhaust - Pressed Rubber Bushing - See New Saturn Video

DiameterPitchRotationMfg Part Number
11 3/812R1331-114-12
 
IF??? your running at 4200 and don't have the boat over loaded.
No amount of moving the linkage or changing timing should increase the rpm's.
You had over 5000 and put a prop that is too steep a pitch and can't expect it to get better performance??

You should have gone to a smaller pitch from a 9 to an 8 to make the engine rev higher.

You just put more strain on an already maxed out system.
You can do damage to the motor if you run like this for extended periods.

You need to beef up the mounting bracket and install a bigger motor.
 
Thanks for your input.
I was just thinking my adjustments are not correct because even before I swapped to the 12P from the 9P
my WOT rpm was about 4700rpm after I reinstalled new shift/throttle cables.
We've had the boat since 2004 and the WOT was about 5200rpms before the new cables were installed.
That is why I'm thinking some adjustments need to be made. The engine does not sound like it is maxing out
at WOT now.

But I do understand your point that going from the 9P to the 12P that I will be losing about 300-400 rpms.
I can accept that as my objective was to increase the top end mph. Albeit only about 2-3mph. :)

And you are EXACTLY correct. I would have to beef up the mounting bracket/stern/transom as it has deteriorated some
since 1996 if I did decide to put a heavier bigger engine on. But I'm not sure that is the wisest option for a 1996 model.
But it would be nice if I fell into an awesome deal for a 90hp or a 115hp. Wishful thinking never hurts huh?
 
The deals are there.
I just ran across a FREE boat and trailer.
The motor and controls(50hp) is worth 500$ all day.
Look on Craigslist.
 
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