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Author Topic:   Propeller: Montauk 170 with 115-HP 4-stroke
Marsh posted 07-11-2004 02:32 PM ET (US)   Profile for Marsh   Send Email to Marsh  
Next week I am scheduled to repower my 2004 Montauk 170 with a Mercury 115-HP 4-stroke EFI engine. I currently have the Merc 90-HP carburetor 4-stroke with the factory stainless prop. My boat rigger says I should be fine after re-power by using the same prop. Any thoughts?

I do not know the dimensions on my current prop, but at WOT, the 90-HP engine will bury the tach well past 6000 RPM. Observed top speed with the 90 engine using a GPS was 41 MPH.

Thanks for any thoughts/observations,

Moe posted 07-11-2004 03:37 PM ET (US)     Profile for Moe  Send Email to Moe     
The 90 four-strokes on the very first 170s had the higher 2.07:1 gearing, like the 115HP, and as a result, came with a lower 16" pitch prop.

It wasn't long before the 90s began shipping with the lower 2.33:1 gearing of the 75HP, and could pull more pitch, so they began coming with an 18" pitch prop.

The more powerful 115HP should do okay with its 2.07:1 gearing and the 18" pitch prop that came with your '04 170, but it also may be able to pull even more pitch and still keep the rpm up in the recommended range.


AQUANUT posted 07-11-2004 09:41 PM ET (US)     Profile for AQUANUT  Send Email to AQUANUT     
2004 montauk, 2004 115hp EFI, vengeance 14p, wot 6100, gps 44.6mph. gets there quick!!!!!!!!!!!!!!!
Marlin posted 07-12-2004 09:23 AM ET (US)     Profile for Marlin  Send Email to Marlin     
The 160 Dauntless with a 115 4-stroke comes with a 16" stainless Vengeance. Top speed could probably benefit from slightly more pitch, but when loaded the Dauntless has to work a little bit to get on plane. With the lighter, easier-to-plane Montauk, it seems like the 18" prop would make a good choice.
jimh posted 07-12-2004 08:21 PM ET (US)     Profile for jimh  Send Email to jimh     
Does the Vengeance series come in even pitch numbers?
AQUANUT posted 07-12-2004 11:28 PM ET (US)     Profile for AQUANUT  Send Email to AQUANUT     
Yes Jim,
the vengeance series is only in even numbered pitch sizes.
contrary to the usual and norm in the industry...WHY?
I really couldn't tell you..this nut is befuddled!

usually even is linked to four blade propellers
odd to three blade props

go figure?

LHG posted 07-13-2004 02:38 PM ET (US)     Profile for LHG    
Almost all of Mercury's SS props for the 4 1/4" 75-125HP gearcases come in even numbered pitch. The highest pitch Vengeance is 18", and then you move into the 20", 22", 24" and 26" performance lines, most notably Laser II and High Five. The only two exceptions to this are the 17" and 19" 4 bladed Trophys, which don't have much application to Whalers.

On any of these engines, the 18" Vengeance is not indicated for speeds over 40 MPH (2-stroke) and 45 MPH (higher reving 4-strokes). Which once indicates for speeds faster than that, you need the more progressive pitch, rake and blade geometry of the Performance props.
If your boat does over 30 mph, an aluminum prop is a waste of money if you care about efficiency, mileage and getting the maximun from your engine purchase

davej14 posted 07-13-2004 03:50 PM ET (US)     Profile for davej14  Send Email to davej14     
Don't leave us hanging, what should we purchase??
Marsh posted 07-13-2004 10:34 PM ET (US)     Profile for Marsh  Send Email to Marsh     
Well, I'm gonna stick with the SS prop off of my old 90 4 stroke, at least for now. Don't know the pitch or diameter, but it definitely is a stainless steel prop.

Boat is being rigged tomorrow, so I should be able to test and report this weekend, if not sooner.

Can't wait...anxiety rules.


LHG posted 07-14-2004 03:14 PM ET (US)     Profile for LHG    
That factory SS prop is an 18" pitch Mercury Vengeance. I understand it will work with the 115 also, because the 115 has a higher (numerically lower) gear ratio. I don't know whether the Merc 115 EFI will turn up a 20" Laser II/High Five on a 170 Montauk.
dogfish2 posted 07-17-2004 12:12 AM ET (US)     Profile for dogfish2  Send Email to dogfish2     
I, too, went from the carburated Merc 4-stroke 90 hp the the more efficent 115 4-stroke EFI. Our resident prop "expert" Sal, recommended the 13.25 X 17 Stilleto for maximum speed and efficiency. Under optimum conditions, I was able to reach 49.5 mph (gps), when other recommended propellers were only able to reach 43-44 mph. I think you will be pleased with the Stilleto's performance. Please email me if you have any other questions.

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