Need help selecting the best prop for towing and watersports

[sealyon]

Hi all, I recently purchased a 2005 22' open bow runabout with the Mercruiser 350 Mag MPI and Bravo 1 with 1.65:1 gear ratio. The boat came with the factory stainless 3 blade 15-1/4 x 19 prop which does ok and seems to meet the recommended WOT tach range. Our primary use is watersports towing so the top priorities are a good hole shot and good mid range speed efficiency. I absolutely do not care about max WOT speed because I do not drive my boat that way. Not knowing anything about props, I experimented with a 14-1/2 x 17 four blade and found the hole shot and speed control to be much better but was way under propped based on WOT tach. I have used several different prop calculators and have narrowed the selection down to basically two props. The first candidate is a 15-1/4" x 18 four blade prop; keeping the same diameter as the origional, adding a blade and dropping 1" of pitch. Candidate #2 is a 13-1/4" x 19 five blade prop; keeping the current pitch, adding 2 blades, and reducing diameter by 2". I was hoping someone has some input or could share their experiences regarding pitch vs. diameter vs. # of blades. THANK YOU!

 

[Bondo]

Candidate #2 is a 13-1/4" x 19 five blade prop; keeping the current pitch, adding 2 blades, and reducing diameter by 2".

Ayuh,.... Welcome Aboard,..... My guess is, option #2 is an outboard prop that don't fit yer drive,....

Never seen a Merc I/O prop under 14" diameter,.....

 

[spoilsofwar]

Go with #1. I use a four blade on my boat, down 2" of pitch from the factory three blade 23p prop, and I like it much better this way. I would have stuck with the "add a blade, drop and inch of pitch" rule of thumb but it seems 22p four blade props are harder to find and only available in stainless and I like to use aluminum.

I find I didn't have to give up too awful much on the top end with the four blade, but the holeshot and reduced planing speed is more then worth it to me.

 

[steelespike]

Marine motors work very hard; like a car pulling a trailer up a never ending hill.
We need to select a prop that allows the motor to rev freely within its wot rpm range.
Regardless of your preferences for speed and performance.Your motor needs to be able to operate within the wot rpm range.
we need to know your wot gps speed and rpm.Diameter is a secondary consideration. If a prop is listed for your drive train the diameter
should be correct.If you look up various props you may notice that as pitch goes up diameter usually goes down you may notice that as you
add blades diameter goes down.It is usually suggested to reduce pitch 1" when going to a 4 blade.This would depend on the present numbers.
We need to know the wot rpm and gps speed with the 19" ss prop.And the 17"We need to be able to evaluate your numbers.
Once we establish the best wot performance you can operate at what ever rpm/speed you prefer.

 

[SkiDad]

if you are not going WOT then under-propping is fine and a lot of people do it. You just need to make drivers of the boat aware.

i see a lot of folks in my area running the high five prop like you mentioned and they pop right up on slalom. I would be running that on my boat cause I feel it would get the rpm up quicker and that is what you are after.

 

[jimmbo]

Many people swear by the Mercury High5

 

[flyingscott]

Here is how I set-up my boats strictly for waters ports. I use a prop that lets it hit the top of the RPM Range with a full load you will need to be careful running a light load as this set up will allow you to over rev the motor. They should make a 5 blade prop for your outdrive because Mercury is the only manufacturer that makes one. The high 5 is an excellent choice for waters ports as they are one of the best if not the best holeshot prop out there. It also likes to run deep in the water which makes it an excellent choice for an I/O

 

[Yegboats]

Mercury hi-five save some money and get the qst 5 Quicksilver it doesn't come with the hub. Since about 2013 they started putting the pvs venting system on the qst 5