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Author Topic:   Prop Overload
tomol posted 04-08-2002 04:47 PM ET (US)   Profile for tomol   Send Email to tomol  
Or more accurately, brain overload. All this great info on props makes my head hurt. Hopefully, I can get some specific feedback about my situation.

I have a '72 Whatever (16 ft., fiberglass console). Particulars:

100 hp Yamaha 4-stroke
2 battaries
23 gallon gas tank forward of the console
no bench seat

I have a 13 x 19 prop
20-21 knots at 4,000 rpms
25-26 knots at 4,500 rpms
36 knots WOT (5,800 rpms), but I need some chop to get this speed. Glassy water only nets me 33 knots.

I'm getting about 4.5 mpg.

These numbers don't seem right. I rarely go WOT, spending about 80 percent of my time at about 4,000 rpms, and judging by the numbers I'm seeing on this board, it seems like I should be getting better mileage and/or a little more speed.

I've talked to a couple of prop guys locally, and they seem to think I'm o.k.

Can anybody help?

Nate

Bigshot posted 04-09-2002 11:11 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
You are identical to my heavier 17' Montauk with a 70hp Zuki 4 stroke.

Have you weighed that hull? You might have an issue or for S&G try a 21". I find the flat torque 4 strokes prefer a larger pitch than a 2 stroke. My 70 runs better all around when I run a 19" which yields me 5400 on a 5800 redline. When I run the 17" which gets me the 5800 basically everything is 400 rpm's higher in my cruise range as well.

Try a 21"

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