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Author Topic:   Montauk 17, 90-HP: Propeller Selection

Henry posted 07-24-2007 02:28 AM ET (US)
[W]hen I bought my Montauk 17 with a Mercury 90-HP two-stroke Saltwater version it came with three propellers:
1--An aluminum 13 1/4-inch x 17-inch pitch that is a Flo-torq II propeller
2--A Quicksilver stainless steel prop with the number "48727 64 A5 17P." This must be a 17 pitch propeller but I am unsure of the diameter. This prop is not a Flo-torq type prop.
3--A Laser II stainless steel prop with the following numbers "48-16992 22P" Again this must be a 22 pitch prop but I am unsure of the diameter. It is a Flo-torq II prop.
What do the numbers on the Quicksilver and Laser II props mean (other than the pitch designation)?
As I understand it none of these props are the optimum prop for my motor and boat. From what I have read on this forum the 17 pitch props may leave me "underpropped" and the 22 pitch prop may leave me "overpropped." Did I understand what I read correctly?
I have only used the Laser II prop and the boat performs well but could it perform better with a 19, 20 or 21 pitch prop?
I know this has been discussed many times before but I would appreciate a revisit to this subject. Thanks.
Perry posted 07-24-2007 03:48 AM ET (US)
It would be helpful if you provided some performance numbers with the propellers you have tested with this motor on your boat.
Also provide max RPM and speed in MPH you achieved and what kind of load you had when you tested the propellers.
How was the hole shot?
What hole is the motor mounted on?
What is the RPM range for your motor?
What is the gear ratio for your motor?
Are you at sea level?
Does you boat have bottom paint?
jimh posted 07-24-2007 07:38 AM ET (US)
The numbers on the propeller are Mercury part numbers, and the trailer nnP is the pitch designator, as you already deduced.
Do you have a tachometer for the engine?
Tom W Clark posted 07-24-2007 10:01 AM ET (US)
In most cases the "48" indicates a Mercury propeller.
The next five digits are the part number unique to that particular prop.
The "Ax" or Axx" suffix describes the generation of hub used. In this case we see that A5 indicates an older pressed in rubber hub. "A45" is a Flo-Torq hub without vent holes. "A46" and "A47" are Flo-Torq hubs with the PVS vent holes.
The "xxP" is the nominal pitch of the propeller.
Prop number 2 is an out-of-production three bladed stainless steel Quicksilver branded 13-1/2" x 17" prop. It is similar to the current Mercury Vengeance 13" x 18" propeller.
A Montauk with a Mercury 90 really wants a 13-1/4" x 20" Mercury Laser II or maybe even a 13-1/4" x 19" Laser II.
A 13-1/4" x 17" Stiletto Advantage II would also be an excellent choice.
Henry posted 07-24-2007 10:21 AM ET (US)
Thanks for the responses.
Which of the three props will provide the best performance for my boat and motor?
I have read here that a prop which makes a motor "lug" will damage the motor in the long term. Will the Laser II 22 pitch prop make the motor "lug"? Will it have any other adverse effects on the motor, i.e., vibration, noise, etc. ?
Tom W Clark posted 07-24-2007 10:22 AM ET (US)
Henry,
Just go buy an appropriate propeller.
Tom W Clark posted 07-24-2007 10:46 AM ET (US)
Actually the Merc 90 has 2.33:1 gear ratio. The 22" Laser II ought to be about right. What is your WOT RPM with it?
Henry posted 07-24-2007 01:40 PM ET (US)
Tom thanks for that last post. My questions re: using the props I have are based on the prospect of spending $400 to $500 for another Laser II prop. The performance seems good with the 22p and if it won't hurt the motor I would keep using the Laser II 22p prop.
The last time I had the boat out at WOT I noticed the tach was sticking and fluctuating wildly. I have installed a new tach but have not had the boat out at WOT since. Next time I take it out I will note the RPM at WOT and post it. By the way I have taken your recommendation from another thread and ordered a Flo-torq III hub kit. Thanks again for the follow-up.

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Author	Topic: Montauk 17, 90-HP: Propeller Selection
Henry	posted 07-24-2007 02:28 AM ET (US) [W]hen I bought my Montauk 17 with a Mercury 90-HP two-stroke Saltwater version it came with three propellers: 1--An aluminum 13 1/4-inch x 17-inch pitch that is a Flo-torq II propeller 2--A Quicksilver stainless steel prop with the number "48727 64 A5 17P." This must be a 17 pitch propeller but I am unsure of the diameter. This prop is not a Flo-torq type prop. 3--A Laser II stainless steel prop with the following numbers "48-16992 22P" Again this must be a 22 pitch prop but I am unsure of the diameter. It is a Flo-torq II prop. What do the numbers on the Quicksilver and Laser II props mean (other than the pitch designation)? As I understand it none of these props are the optimum prop for my motor and boat. From what I have read on this forum the 17 pitch props may leave me "underpropped" and the 22 pitch prop may leave me "overpropped." Did I understand what I read correctly? I have only used the Laser II prop and the boat performs well but could it perform better with a 19, 20 or 21 pitch prop? I know this has been discussed many times before but I would appreciate a revisit to this subject. Thanks.
Perry	posted 07-24-2007 03:48 AM ET (US) It would be helpful if you provided some performance numbers with the propellers you have tested with this motor on your boat. Also provide max RPM and speed in MPH you achieved and what kind of load you had when you tested the propellers. How was the hole shot? What hole is the motor mounted on? What is the RPM range for your motor? What is the gear ratio for your motor? Are you at sea level? Does you boat have bottom paint?
jimh	posted 07-24-2007 07:38 AM ET (US) The numbers on the propeller are Mercury part numbers, and the trailer nnP is the pitch designator, as you already deduced. Do you have a tachometer for the engine?
Tom W Clark	posted 07-24-2007 10:01 AM ET (US) In most cases the "48" indicates a Mercury propeller. The next five digits are the part number unique to that particular prop. The "Ax" or Axx" suffix describes the generation of hub used. In this case we see that A5 indicates an older pressed in rubber hub. "A45" is a Flo-Torq hub without vent holes. "A46" and "A47" are Flo-Torq hubs with the PVS vent holes. The "xxP" is the nominal pitch of the propeller. Prop number 2 is an out-of-production three bladed stainless steel Quicksilver branded 13-1/2" x 17" prop. It is similar to the current Mercury Vengeance 13" x 18" propeller. A Montauk with a Mercury 90 really wants a 13-1/4" x 20" Mercury Laser II or maybe even a 13-1/4" x 19" Laser II. A 13-1/4" x 17" Stiletto Advantage II would also be an excellent choice.
Henry	posted 07-24-2007 10:21 AM ET (US) Thanks for the responses. Which of the three props will provide the best performance for my boat and motor? I have read here that a prop which makes a motor "lug" will damage the motor in the long term. Will the Laser II 22 pitch prop make the motor "lug"? Will it have any other adverse effects on the motor, i.e., vibration, noise, etc. ?
Tom W Clark	posted 07-24-2007 10:22 AM ET (US) Henry, Just go buy an appropriate propeller.
Tom W Clark	posted 07-24-2007 10:46 AM ET (US) Actually the Merc 90 has 2.33:1 gear ratio. The 22" Laser II ought to be about right. What is your WOT RPM with it?
Henry	posted 07-24-2007 01:40 PM ET (US) Tom thanks for that last post. My questions re: using the props I have are based on the prospect of spending $400 to $500 for another Laser II prop. The performance seems good with the 22p and if it won't hurt the motor I would keep using the Laser II 22p prop. The last time I had the boat out at WOT I noticed the tach was sticking and fluctuating wildly. I have installed a new tach but have not had the boat out at WOT since. Next time I take it out I will note the RPM at WOT and post it. By the way I have taken your recommendation from another thread and ordered a Flo-torq III hub kit. Thanks again for the follow-up.