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MERCURY 80HP PROP

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kjdmoosejaw

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"I just bought my Dad's bo

"I just bought my Dad's boat with a 1979 80HP mercury motor. Had a friend clean carbs, change fuel lines, change plugs, change impeller and seals. Took it out for a run and the old girl ran great ran around the lake for 1.5 hrs without missing a beat - top speed 30MPH at 4500 RPM with a 17 pitch prop. Problem is I got home and backed into a brick wall parking the boat and badly nicked two blades on the prop - about 1.5" x 1" on each blade. Is it better to repair the prop, replace the prop. with an aluminum 17 pitch, replace with a 4 blade 17 pitch or replace with a 21 pitch that came with the boat? I will mostly be using the boat for tubing/skiing/wakeboarding and am not sure if the 21 pitch will give me enough pulling power.
(Unfortunately I cannot try the 21 pitch out before we leave on a week long holiday with the kids)"
 
"start here with prop wizard/c

"start here with prop wizard/calculator, i just went thru this myself.

http://www.marineengine.com/parts/prop/prop_wizard.php

for what its worth , i'll yield to the pros here on this but what i learned


WOT (wide open throttle)- is usually 4750rpm- 5250rpm and the best operating range
now as pitch goes up your rpm's should decrease reduced torque and hole shots
now a 21 pitch will be below were you are now in rpm (tach's on older boats r not so reliable)
now 17 pitch is better for loads, 21 for cruising
prop link should guide you more
maxx"
 
"I'd look around for a 15

"I'd look around for a 15 pitch. Try eBay. Lots of them araound. A 15 would tow far better, and you're not getting enough rpms with the 17.

Jeff"
 
"Kerry Jeff's right your e

"Kerry Jeff's right your engine is not getting enough revs, drop down to a 15p and dont use the 17 and especially the 21p it will be the quickest way to detonate a piston."
 
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