Prop Selection - Bayliner 175

[Stinnett21]

That's a 4 1/4 prop meaning exhaust (at least a good amount of it) travels over the outside of the hub causing ventilation. This is at least some, if not all, of your issue.

 

[jlh3rd]

Your point on the compression test is interesting. When I performed my test the throttle plate was in neutral/idle position and the other non-testing cylinder plugs were still installed. You have me curious if this makes a material difference, so I'll re-run my compression test with those 2 setup changes (throttle plate open and all plugs out at same time).

It's just what I've always been told.
But all miscellaneous issue should be fixed before spending money on props.
And agreed, if that prop hub/gearcase isn't a match, it won't work.
and see pic.. mine is black. maybe you don't need one.

 

[gsbarry]

What do y'all think about this prop for my application?

 

[alldodge]

Your original 17P 4 blade is equal to a 19P 3 blade
Going to a 19P 4 blade is equal to a 21P 3 blade

Forget the 4B and go 3 blade

 

[Stinnett21]

Ageed, stay with a 3 blade for your application. Solas, Turning Point or Michigan would be good choices. Mercury props are great but this application you're not going to notice a difference to justify the added cost. Getting the pitch dialed in is the key. And as stated above it may be wise to have two, one for light loads and another for water sports pulling.

 

[gsbarry]

Thanks for the feedback on the 3 blade. I respect y'alls opinions but I'm left a little confused on the recommendation. This may be because I didn't really talk about my typical boating conditions and performance desires. Typically, the lakes/time of day that I plan to boat on are fairly choppy from either weather or boat traffic, or both. Also, I personally put more emphasis on low end torque and hole shot rather than top end. From my reading a 4 blade provides better handling at low speeds, and improved hole shot, sacrificing top end, which in my mind is similar to going down in pitch. So I'm confused when you say a 19P 4 blade is equal to a 21P 3 blade, I would have thought it was the opposite, that a 21P 4 blade would be equal to a 19P 3 blade. What is it about my application that makes 4 blades a poor choice? Just trying to learn and understand.

 

[gsbarry]

How about this 3 blade? The cost of the merc/quicksilver seems pretty similar to Michigan Wheel and Solas. From what I've read the Alpha 1 can fit a 14 1/2" diameter. Thoughts on the Flo Torq II hub? For the extra $60 kit, seems like cheap insurance against driveshaft damage from strikes along with improved shifting and vibration (maybe this is not all that noticeable).

 

[alldodge]

@gsbarry if you look long enough no matter what anyone tells you there is somewhere else which will provide a different set of facts or opinion. Your posting above is true but also need to know where it was taken from. The question of where is need to determine how it was presented.

Saying a 4B provides better hole shot and better handling at slow speeds "IF" (note the if) your talking about a light boat with sufficient power. Your boat as 1 of the 2 items mentioned. It is a light boat but does not have sufficient power.

It is correct a 4B has more surface area and therefore has less slip. Slip is good and bad. Good so every turn of the prop bits in hard and moves the boat forward (with sufficient power) more efficiently. Bad because a motor needs to get the rpm's spun up fast to get into the torque band. So 4B does not allow the rpm's to come up fast.

The 3B has less area and has more slip. Good is with more slip the prop spins faster sooner and gets the motor into the torque band. Bad is more slip

So the rule of thumb due to differences in surface area, a 4B pitch equals a 3B with 2 inches of pitch added.

On a light boat a 4B will also provide more stern lift. Lift can be good and bad, and all depends on the boat

Last thing keep reading and find areas where folks here have provided input. Go elsewhere and read those things. When done decide which one you want to go with and try it. Only ask when done is make sure to come back and let us know what you did so the answers will be here for the next guy looking

Good luck

 

[Pmt133]

Depends on the 4 blade and depends on the 3 blade what happens. Similar sized 4 blades will usually need less pitch than a 3 blade. My experience varies after testing a lot of props over the years.

 

[gsbarry]

@gsbarry if you look long enough no matter what anyone tells you there is somewhere else which will provide a different set of facts or opinion. Your posting above is true but also need to know where it was taken from. The question of where is need to determine how it was presented.

Saying a 4B provides better hole shot and better handling at slow speeds "IF" (note the if) your talking about a light boat with sufficient power. Your boat as 1 of the 2 items mentioned. It is a light boat but does not have sufficient power.

It is correct a 4B has more surface area and therefore has less slip. Slip is good and bad. Good so every turn of the prop bits in hard and moves the boat forward (with sufficient power) more efficiently. Bad because a motor needs to get the rpm's spun up fast to get into the torque band. So 4B does not allow the rpm's to come up fast.

The 3B has less area and has more slip. Good is with more slip the prop spins faster sooner and gets the motor into the torque band. Bad is more slip

So the rule of thumb due to differences in surface area, a 4B pitch equals a 3B with 2 inches of pitch added.

On a light boat a 4B will also provide more stern lift. Lift can be good and bad, and all depends on the boat

Last thing keep reading and find areas where folks here have provided input. Go elsewhere and read those things. When done decide which one you want to go with and try it. Only ask when done is make sure to come back and let us know what you did so the answers will be here for the next guy looking

Good luck

Thanks for the explanation. That makes sense wrt/ to the lower available power on the 3.0L and the desire to get rpm's up quickly.

 

[Scott Danforth]

You don't have enough motor to spin more than a 15p 4-blade with your current boat

 

[Lpgc]

Your point on the compression test is interesting. When I performed my test the throttle plate was in neutral/idle position and the other non-testing cylinder plugs were still installed. You have me curious if this makes a material difference, so I'll re-run my compression test with those 2 setup changes (throttle plate open and all plugs out at same time).

I agree with Jlh3rd that compression test should really be done with the plugs out and open throttle but that is more likely to increase the pressure reading than anything else - Other plugs removed so other cylinders don't have compression so the starter will crank the engine faster leading to quicker compression so more heat of compression in the cylinder with the pressure tester, open throttle so maybe bit less restriction to incoming air at cranking speed and higher intake / manifold pressure means the cylinder will fill with more air on the intake stroke so have higher pressure on the compression stroke.

Your compression readings seem to be good/normal to me. Compression won't be a factor affecting your choice of prop but if compression were a problem you'd need to look at rebuilding the engine before getting into choosing a prop.

 

[cyclops222]

The only boat with only 1 prop for all running ?
Is a race boat.
All others have at least 2 different props.

 

[Stinnett21]

@gsbarry if you look long enough no matter what anyone tells you there is somewhere else which will provide a different set of facts or opinion. Your posting above is true but also need to know where it was taken from. The question of where is need to determine how it was presented.

Saying a 4B provides better hole shot and better handling at slow speeds "IF" (note the if) your talking about a light boat with sufficient power. Your boat as 1 of the 2 items mentioned. It is a light boat but does not have sufficient power.

It is correct a 4B has more surface area and therefore has less slip. Slip is good and bad. Good so every turn of the prop bits in hard and moves the boat forward (with sufficient power) more efficiently. Bad because a motor needs to get the rpm's spun up fast to get into the torque band. So 4B does not allow the rpm's to come up fast.

The 3B has less area and has more slip. Good is with more slip the prop spins faster sooner and gets the motor into the torque band. Bad is more slip

So the rule of thumb due to differences in surface area, a 4B pitch equals a 3B with 2 inches of pitch added.

On a light boat a 4B will also provide more stern lift. Lift can be good and bad, and all depends on the boat

Last thing keep reading and find areas where folks here have provided input. Go elsewhere and read those things. When done decide which one you want to go with and try it. Only ask when done is make sure to come back and let us know what you did so the answers will be here for the next guy looking

Good luck

Quicksilver props are Mercury props marketed under a different name so they can be sold at retail outlets rather than dealerships (or something like that, I'm not a marketing exec). They are also sold without the hub kit, thus the lower price than a Mercury. Sounds like you need the hub so might as well buy Merc. Quicksilvers have different names but you can google the equivalent. The Quicksilver Black Diamond is the Mercury Black Max, the Quicksilver Nemesis is the Mercury Spitfire, the Quicksilver Q3 is the Mercury Enertia, etc.

 

[gsbarry]

You don't have enough motor to spin more than a 15p 4-blade with your current boat

Scott, are you saying 15p is the lowest number you would go with? Or the highest number?

 

[dingbat]

The only boat with only 1 prop for all running ?
Is a race boat.
All others have at least 2 different props.

You can add most properly sized, and "fully" powered (rated HP) boat, to that list as well

Prop changes are used to compensate for a lack of horsepower at RPM.
Unfortunately, a large percentage of boats sold are under-powered to met a price point, thus the perception that it's normal operation for everyone

 

[jlh3rd]

Thanks for the feedback on the 3 blade. I respect y'alls opinions but I'm left a little confused on the recommendation. This may be because I didn't really talk about my typical boating conditions and performance desires. Typically, the lakes/time of day that I plan to boat on are fairly choppy from either weather or boat traffic, or both. Also, I personally put more emphasis on low end torque and hole shot rather than top end. From my reading a 4 blade provides better handling at low speeds, and improved hole shot, sacrificing top end, which in my mind is similar to going down in pitch. So I'm confused when you say a 19P 4 blade is equal to a 21P 3 blade, I would have thought it was the opposite, that a 21P 4 blade would be equal to a 19P 3 blade. What is it about my application that makes 4 blades a poor choice? Just trying to learn and understand.
View attachment 405452

"So I'm confused when you say a 19P 4 blade is equal to a 21P 3 blade, I would have thought it was the opposite, that a 21P 4 blade would be equal to a 19P 3 blade."


when you add a blade, that is the same as increasing the "bite" (pitch). So to equal out, you would add pitch (or diameter) if you remove a blade. It works the same with diameter. If you increase diameter, you are increasing the"bite".
I get the same performance #'s with my Merc 4-14x14 and 3-16x13.
this is what makes propping so much fun...and expensive.

 

[cyclops222]

Even a USCG bowrider with a maximum Hp motor. Mine Stil needs 2 props.
1 for only me doing WOT and turns.
1 for 6.... 200 pound seniors on a fast cruise to a picnic.
I change props at the dock in 5 minutes.

 

[gsbarry]

Even a USCG bowrider with a maximum Hp motor. Mine Stil needs 2 props.
1 for only me doing WOT and turns.
1 for 6.... 200 pound seniors on a fast cruise to a picnic.
I change props at the dock in 5 minutes.

For my application, what kind of pitch spread would y'all generally expect going with a 2-prop approach? (One prop for fully loaded slower speeds, and one prop for unloaded higher speeds). I get that it's hard to say exactly without testing, but just in general. Are we talking 2" pitch difference between the "fast" and "slow" prop? Or something more dramatic like 4" or 6"?

 

[Scott Danforth]

Scott, are you saying 15p is the lowest number you would go with? Or the highest number?

15p in a 4 blade is the highest I would consider.

"So I'm confused when you say a 19P 4 blade is equal to a 21P 3 blade, I would have thought it was the opposite, that a 21P 4 blade would be equal to a 19P 3 blade."

adding a blade is like adding 2" of pitch. adding blades and adding pitch both add load to the motor requiring more torque at a given speed.

For my application, what kind of pitch spread would y'all generally expect going with a 2-prop approach?

I had 3 props in my 3.0 powered boat (see post #11). and pulling skiers, I still had to have most of the people toward the front to get a good hole shot.