9.9 hp + big boat which prop and pitch is for me?...

[jvolpe28]

Hello all, I have a 16 ft MFG boat fiberglass and deep, kind of heavy for my motor, 1984 9.9 evinrude, The lake I fish on has a 10 hp limit. My current prop is a 9 1/2 x 10 . For such a heavy load what prop would be best for my situation, I was wondering what dia + pitch to get...thanks for any help

 

[Spidybot]

Re: 9.9 hp + big boat which prop and pitch is for me?...

Describe how it works. Does it overrev? Do you have problems getting rpms up? Does it sound like working hard all the time?<br /><br />Most of these small motors are sold with 'universal' props. If it reaches the right rpm range at WOT you're using the right prop already.

 

[Capn Mike]

Re: 9.9 hp + big boat which prop and pitch is for me?...

UU's right: if your motor is achieving the correct rpm, changing props wouldn't make any difference. You probably have a motor with gearing and prop designed to make a little boat go as fast as possible.<br />What you need to do is "switch out" (OK, that probably means buy a different motor) your gears. Small motors designed for big boats have lower gears so they can turn a steeper-pitched prop at optimum RPMs; I have an older Yamaha 9.9 4-stroke geared for houseboats/pontoon boats that pushes my 5000 lb fishing boat at hull speed. A motor like yours would roar away, but because of the higher degree of pitch it wouldn't be moving the water as well (make a nice daquiri blender, though).<br />Come to think of it, maybe it doesn't mean buying a different motor. Does anyone on this forum know if jvolpe can switch the gears in his motor so he can run a deeper-pitched prop?

 

[oldboat1]

Re: 9.9 hp + big boat which prop and pitch is for me?...

For comparison, you might check out the Sailmaster model (think that was the name) for that model year, or something close. Check the prop size. Additionally, you might be able to find a lower unit from a parted-out sailmaster engine, and substitute the lower unit (without the shaft extension, if you prefer, using your current driveshaft with the gearcase and prop from the sailmaster.)<br /><br />just an idea.

 

[Spidybot]

Re: 9.9 hp + big boat which prop and pitch is for me?...

Yeah. Capn Mike made my brain tune in on my outboard archive. The 9.9 came with 3-blade 9.5x10 or 9.25x8 props. Gear ratio is 12:29 for all types.<br /><br />Still it doesn't tell if jvolpe needs to change. 9.25x8 will allow his motor to rev easier - but also has less blade area. For heavy load you'd normally go for lower prop rpm with larger blades, but this really isn't an option with a 9.9<br /><br />The 4-stroke makes another job, it's a different motor and the 9.9 Rude cannot be expected to perform like it.

 

[Capn Mike]

Re: 9.9 hp + big boat which prop and pitch is for me?...

Doesn't matter whether it's 2 or 4-stroke; he can come real close with the right gears. What he needs are gears that allow him to turn a bigger prop at the higher rpm than his existing one would allow. I like Oldboat's suggestions; I believe it was called the Sailmaster, designed for pushing big displacement sailboats with just a little horsepower. If jevolpe can't find it locally, try Google; I did, and found lots of suggestions, including http://www.maxrules.com/fixomcindex.html who claims to really like old motors. This could be a great project!