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Author Topic:   Yamaha prop size question
Tom Byrum posted 02-15-2001 10:37 PM ET (US)   Profile for Tom Byrum   Send Email to Tom Byrum  
I have no marks on my Yamaha props other than 17-K. Does anybody know what this means? Ebay has a pair of polished stainless props size 13 X 18 and I am wondering how they would work. (18 outrage with twin Yamaha 70s)
Hoop posted 02-16-2001 12:35 AM ET (US)     Profile for Hoop  Send Email to Hoop     
Tom, I found the 14x17 prop dimensions embossed on the ring that is just under the retaining "nut" assembly. eg: I had to remove the cotter pin and nut to read the dimensions on the prop. Maybe this is the case for your prop? Hoop
lhg posted 02-16-2001 01:10 AM ET (US)     Profile for lhg    
On most outboard props, I have always selected by the pitch, and let the prop designer deal with the respective diameter, which can often vary and is a complicated relationship. Gear case/hub diameter determines the series of prop that will fit a given engine.

My guess is that the "17" means 17" pitch. On Mercs, they always stamp the pitch on the hub, with a 17P mark.

If you are running standard elephant ear props, at the TOP of the RPM limit lightly loaded, they say to go up for the performance SS type. So those 18's would work and give you a little more speed and handling. Otherwise stay the same or go down 1 pitch.

Curious, Tom. What kind of speed and mileage to get from the twin 70's? I'd guess maybe 42mph? Seems like just about the perfect power/mileage combination for an offshore running 18.
Or do you wish you had a pair of the same size Yamaha 90's?

Incidentally, your boat looks really nice, in great shape. And rare, with those twin engines. I've only seen about 5 18's ever with twins.

Tom Byrum posted 02-16-2001 10:13 AM ET (US)     Profile for Tom Byrum  Send Email to Tom Byrum     
Thanks guys. Larry you guessed my top speed pretty close. I dont know my mpg as I have never checked. I do know that whatever the difference in mileage is for twins is well worth it. When I have to repower in the future it will be at least 90s maybe more. I may trade up to a 22 though I'm not sure. I dont want to end up like my partner that traded his Montauk for a Grady. He used to be fishing every weekend like me but now he probably only gets out 6 or so times a year.
rwr123 posted 02-26-2001 10:53 PM ET (US)     Profile for rwr123  Send Email to rwr123     
I was in a friends 17 Montauk with 100 hp new YAMAHA 4 Cycle
Was that ever fun 21 prop

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