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  Some "hard" GPS speeds with Montauk 70-HP.

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Author Topic:   Some "hard" GPS speeds with Montauk 70-HP.
Bigshot posted 02-20-2002 11:05 AM ET (US)   Profile for Bigshot   Send Email to Bigshot  
Here are my findings with my 1989 Montauk, bottom paint, full 27-gallon Pate, 6-in. Jackplate and 1999 70-HP Evinrude (Suzuki) 4-stroke. It was me and my wife (I weigh 200 she weighs MYOB:) It was moderate chop and about 72-degrees.


14x17 Alum prop:
5800....35 (WOT)

13x19 alum prop
5500....39 (WOT)

Pretty substantial I would say. I have never experienced 2 inches of pitch that made that much of a difference. Holeshot was great with both props. As some know I was slightly disappointed in my slow speed with the 70 over my 90 Yamaha....until now. I was running 3800 RPM with the Yamaha and doing 28 MPH. I then changed motors and at 3800 I was doing a measly 21 and it felt like I was falling off plane. Now I am running 3800 and doing! The 19-inch had less bow rise than the 17-inch. The blades look different and the 17-inch blades are longer as in it would not fit in a 5-gal. bucket but the 19 did. I am gonna run these numbers by my prop shop (General Propeller) in Bradenton and see what he recommends as far as turning my 17-inch Yamaha SS prop into that would benefit me the best.

FYI with 4 people in the rig it popped on plane nicely with the 19-inch, cruised very nicely with the load and hit a respectable 34 but only at 5000 RPM (WOT). So in that respect it is a bit steep. A 18-inch would probably be ideal.

I was amazed that a 14x17 prop had a slower cruise. I assumed the larger diameter would give a better midrange but it did not. I guess 1-inch diameter is not enough to make a difference or the Montauk is light enough that a large diameter blade is inefficient.

I am gonna post my SS prop speeds when I get them and will also do now and jackplate up another inch or so.


peteinsf posted 02-20-2002 12:37 PM ET (US)     Profile for peteinsf    
Thanks for the detail bigshot, I love having "GPS" data for my prop chart! All you need now is a fuel flow meter for some real MPG numbers.
Bigshot posted 02-20-2002 12:43 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
who wants to donate a Floscan?
hauptjm posted 02-20-2002 03:50 PM ET (US)     Profile for hauptjm    
BS, if I find one, you can keep it with your fade meter. :)
Bigshot posted 02-20-2002 04:41 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I'll store it right next to my collection of muffler bearings.
dgp posted 02-20-2002 07:01 PM ET (US)     Profile for dgp  Send Email to dgp     
BS, you can lubricate those with relative bearing grease.
jimh posted 02-26-2002 12:53 AM ET (US)     Profile for jimh  Send Email to jimh     
[Edited post to improve readability--jimh]
Bigshot posted 02-26-2002 02:01 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Looks good...Thanks Jim.

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