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Author Topic:   stainless prop selection for 170
fitn217 posted 06-06-2003 12:03 PM ET (US)   Profile for fitn217   Send Email to fitn217  
I'm looking to purchase a stainless prop for my '03 Montauk 170. My current prop is the stock aluminum one which I plan to use as a spare. The numbers on the prop are 48 77348a45 21P. Should I go with the same size in stainless? I'm getting 5400 rpm and 42 mph according to GPS with the stock prop.
I would like to thank everyone for their imput on this website because it has helped me immensly in purchasing and using the boat.
Perry posted 06-06-2003 01:01 PM ET (US)     Profile for Perry  Send Email to Perry     
It really makes it helpful if you state what brand motor and the HP, so others with the same set-up may be able to contribute info.
Bigshot posted 06-06-2003 02:09 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Being it is an 03....we all know it MUST have a Mercury.

Knowing the redline is most important and when you get 5400 is that no fuel and just 1 person aboard? If redline is 5200 then yes I would get a 21P SS and bring it down to redline. If redline is 5700 then I would probably step down to a 19 or 20" SS.

lhg posted 06-06-2003 02:35 PM ET (US)     Profile for lhg    
With Mercury's SS performance line props, you get even number pitch with the mid-range 4 1/2" gearcase. In addition, the propellers take a "big bite" on the water, so I would drop down to a 20" pitch, either Laser II if top end matters, or High Five, if smooth pulling power & hole shot is the objective. There will be no top end loss at all, and it will probably be improved in spite of the lower pitch. In either case, have the engine set up in the middle/3rd holes. Mercury does not make conventional "elephant ear/Vengeance" SS props above 18" pitch, instead moving the buyer into the performance ranges of 20-26" pitch. That should tell us something about prop choice and application.

This is why all of the Montauks are coming with aluminum props, to get the necessary pitch without the $300 price upcharge for a performance line SS.

fitn217 posted 06-07-2003 11:31 AM ET (US)     Profile for fitn217  Send Email to fitn217     
oops....the motor is a mercury 90 2 stroke, I knew I was forgetting something. thanks for the help
fitn217 posted 06-07-2003 11:36 AM ET (US)     Profile for fitn217  Send Email to fitn217     
I'm getting 5400 rpm with two people and full 25 gallons of fuel, motor fully trimmed out. According to the Mercury owners manual full throttle rpm range is from 5000-5500 rpm.
Sal DiMercurio posted 06-07-2003 07:14 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
If your getting 5,400 rpms with 2 guys & 25 gallons of fuel, you might think about leaving well enough alone as your redline is only another 100 rpms.
Perry posted 06-07-2003 09:33 PM ET (US)     Profile for Perry  Send Email to Perry     
The same size prop in stainless will probably give you less rpm at WOT because they are cupped and are more efficient. So like Ihg says, A 20 pitch performance prop might put you around 5500 rpm.
fitn217 posted 06-07-2003 10:19 PM ET (US)     Profile for fitn217  Send Email to fitn217     
Sal will the same size pitch(21) in stainless give me the same performance or should I go with the 20 pitch since the stainless prop bites better.
I'm pretty happy with the stock setup the boat runs great with two adults on board. BUT (there's always a but) with the third adult behind the console and all the weight at the stern getting up on plane and cruising at slower speeds is much tougher as the bow rises a lot higher until an acceptable cruising speed is reached and the boat levels out.
Is there a prop that would help improve my hoeshot and allow the boat to plane at a slower speed with all of that weight at the stern and nothing in the bow, or should I get the same size prop in stainless.
I use the 170 montauk in an often rough Raritan bay and the ocean.
Sal DiMercurio posted 06-08-2003 01:29 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Ihg is right.
The stainless should bite better & could be a little to much at 21p, i also agree the 20p would be your best bet.
I would get the smallest diameter by 20p I could put on the engine, as you really don't need a 14.25 or 15 x 20.........see if you can find a 12.75, - 13 or 13.25 x 20p.
Matthew posted 06-08-2003 01:52 AM ET (US)     Profile for Matthew  Send Email to Matthew     
fitn 217,

I have the same setup as you and stuck with the 21p when trading up from aluminum to stainless. I'm right at 5500 rpms. The prop is pre-laser II and vengeance, but I was able to find a new one for a reasonable price. Although the top end numbers between the stainless and aluminum props were close, the boat performs better running the SS.

After testing a 19p of the same vintage and turning 5800 rpms, the decision to keep the 21p was evident. When I put the model number of the prop I purchased into Mercury's Parts Express,it directed me to the Laser II 20p as the replacement. A good prop shop will let you run one before you buy.

The boat will plane quicker if you put the third guy on the cooler, give him a throwable seat cushion so he can take care of the reels with his back ;).


fitn217 posted 06-09-2003 12:21 PM ET (US)     Profile for fitn217  Send Email to fitn217     
Sal,Perry,IHG,Matt & Bigshot thanks a bunch for your help. I'm going to call the dealer and get a few price quotes and do a few test runs. I'm also going to have to retrain my friends to sit in the bow, as they are shy after continuously getting soaked in the bow of my fathers Nauset. New hull = no more pounding and no more wet rides.
I ordered my 170 without the fishing package and put perko railmount rod holders on the console grab rail. Works great keeping the rods out of the way. $32 a pop you can't go wrong although it does add up when you buy 10 of them like I did. I put 4 on the console grab rail and the others on the railings around the boat.
lhg posted 06-09-2003 02:31 PM ET (US)     Profile for lhg    
For the conditions you are describing, you may want a 20" pitch Mercury High Five propeller (about $400 bought right) for better hole shot, planing at slower speeds, and great holding in rough water. In addition, you can choose the optimal vent plug size for additional acceleration if needed.

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