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Hello..

Just bought a 2004 170 Montauk with 90 HP Merc 2 stroke. Looking to upgrade prop from Aluminum to stainless to be used in salt water..

Looking for an improvement on quicker acceleration for planning.

Any recommendations on size and pitch? and brand? Keep with Merc?

Thanks for your time...

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http://boatpropellers.iboats.com/Mercury/90_HP_(1978Newer)_15.00-Pitch_HR_Titan_1453-133-15_Propeller/282/7290/?cart_id=779498834

I run this prop on my 17 montauk with a 115 Evinrude etec. It leaps out of the water and pulls a 220lb slalom skier out of the water in 3 seconds. Also this prop handles tight turns with little cavitation. Some here will say that set up is under propped and to some degree they would be right. However the amount of gear and a full cooler add a good bit of weight and this set up laughs at all of that. Do I hit 50mph, no I don't, but that's not what I'm after. 42mph is about it and plenty fast in this boat. Lastly on the four blades vs three, I've tried both and prefer the four blade hands down. Better grip in turns and less vibration at lower speeds. Hope this helps but another thing to consider is how you use your boat and how much weight you usually carry.

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Thanks.. never thought of a 4 blade...
No issues with your 115HP as the boat is rated for a max of 90hp? engine weight is usually the same for 90 & 115...

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A 2004 Mercury 90 with its 2.33:1 gear ratio will make good use of a 13-1/4" x 20" Mercury Laser II or a 13-1/4" x 19" Stiletto Advantage 4.25 (aka Turbo 1).

Whether one chooses a three blade or four blade propeller depends on the model of propeller being considered. Propellers are not generic pieces of hardware that can be simply described by number of blades and pitch.

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I had to mount the motor myself, no dealer would exceed the max hp. It weighs 368, 40 pounds less than a Honda 90 hp four stroke that you see on a lot of montauks. We do a lot of skiing with this boat and the extera horses help with deep water starts. Nj marine police have been putting 115's on this hull for a long time so it must ok. My insurance company knows its overpowered and wrote the policy anyway.
I see Tom recommends a 19 or 20 pitch prop and while he is a guru of sorts I have to respectfully disagree. You'll have trouble reaching max recommended rpm's with that much pitch. Try one and see.

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Please explain why.

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I tried a 13 1/2 d x 19 p Apollo stainless 3 blade and could only get 5100 rpm. My gear ratio is 2:1 a little different than your Merc. Evinrude specs are 5500 - 6000 rpm for this motor. But like I said you'll have to take into account how much weight you usually travel with. I carry 24 gallons of gas, 4 or 5 people, a cooler full of ice and beverages, anchor,rear bench, forward platform and all the gear to keep the Coast Guard happy. If the boat was empty with 5 gallons of gas and just me in it a 19p propeller would probably work and be scary fast. But that's not how I use my boat. Props are something you have fit specific to your needs.

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I agree that the prop you choose needs to fit your needs, but it also needs to fit your boat and motor. This is why what works on a normally loaded 2004 Montauk 170 with a Mercury 90 may be very different from what works on a heavily loaded classic Montauk 17 with an Evinrude E-TEC 115.

- Different boat
- Different brand of motor
- Different horsepower
- Different gear ratio
- Different engine speed range

Pretty tough to draw conclusions about one from the other.

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Thank you all for the feedback. I bought a Laser II 13.25 x 20 SS on ebay. Lets see how it goes...

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As a follow up. The Laser II works great.. Nice performance at WOT - 5500rpm.. Speed will vary according to engine trim and load.. but overall good performance.

Thanks for the advice Tom.