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post #1 of 11 (permalink) Old 09-18-2012, 12:47 PM Thread Starter
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kicker motor prop pitch?

I have a 9.8 four stroke that I use on a HP restricted lake and on the river when it's too icy for the jet. When I had my 14' boat it did fine. Nowadays, it's trying to push my 1655 Roughneck with 2-3 guys, gear and several dozen goose decoys.
I want to get a lower pitch prop to help push my rig. I can go down as low as 5 on the pitch, also can get 6.5, 7 and 9 pitch props.
I know no matter what prop I put on it, it's not going to plane my rig, just want to get the most bang for the buck, so to speak out of a new prop.
Is it going to be too extreme to go to the 5 pitch prop? Don't want to experiment too much, or make the wrong selection when props are 60-90 bucks a pop.
Thanks in advance for any help.
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post #2 of 11 (permalink) Old 09-18-2012, 09:08 PM
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Re: kicker motor prop pitch?

Two things to think of first. What pitch is currently on it and what are the RPM's at WOT. It's not so much how fast you go, but what RPM's the motor is running at. If you drop the pitch too much you'll over-rev the engine(BAD!!!), too high a ptich and the motor will lug. Best thing to do is find the specs, they will give you a WOT range, and if you don't have a tach. then find a portable one.

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post #3 of 11 (permalink) Old 09-19-2012, 09:21 AM Thread Starter
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Re: kicker motor prop pitch?

Trap,
Thanks for the link for the tach. Had no idea you could get one for that price.
Motor is definitely not running at rated speed as it now stands. It is a Nissan (Tohatsu) 9.8 four stroke, rated for 5000-6000 rpm at WOT. Definitely not getting any where near that now. With out a tach, I can only guess, but I don't think I'm even getting 4000 rpm at present.
Reading up on pitch a little, looks like you can gain 100-200 rpm per drop in pitch. Standard prop on the nissan is 8, built for high end speed on a small boat. If I go to a 5 pitch, thats a 3" drop on pitch, which shouldn't translate to more than a 300-600 rpm gain, so I should be fine. I'm gonna get a tach to be on the safe side, but from everything I can figure, I should be golden with the 5" pitch kicker prop. Additionally the motor has an over rev protection, so I have a built in safety there as well.
Thanks.
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post #4 of 11 (permalink) Old 09-19-2012, 10:16 AM
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Re: kicker motor prop pitch?

With props, the number of the pitch is actually confusing. The lower the number, the less the rpm, but the more power you will have. The higher the number, the higher the rpm and the more top end speed. For example, when I had an 85 hp johnson on one of my boats, I ran either a 17 or 19 prop depending on what I needed it for. The 17, less rpm, more power, the 19, more rpm and more top end speed.

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post #5 of 11 (permalink) Old 09-19-2012, 02:48 PM Thread Starter
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Re: kicker motor prop pitch?

Octagon,
This is a quote from boatingmag.com, and the way I read it, lowering pitch will raise my motor RPM's, lower top speed but get me more torque. I am diving into this for the first time, but as I understand pitch and diameter, with an equal diameter prop and a lower pitch, I should pick up RPM and torque to be able to better push my boat.
"Pitch is defined as "the distance a propeller would move in one revolution if it were moving through a soft solid, like a screw through wood." For example, a 21-pitch propeller would move forward 21 inches in one revolution.

Think of a propeller as you would a car's axle ratio. The lower the ratio, the more pulling power from a standstill. The same is true with a prop. The lower the pitch, the better your hole-shot. However, this comes at a price: top speed. The lower pitch makes the engine reach maximum rpm at slower speeds.

Conversely, a higher pitch will deliver greater top speeds, but slower acceleration. Be aware that lower-horsepower engines can bog down if fitted with a propeller with too high a pitch and diameter, and that can wear heavily on internal engine parts.

If you're changing pitch on a recreational boat, remember that each inch of pitch is worth about 200 rpm. Lowering the pitch will increase rpm and vice versa. For example, going from a 23 pitch to a 21 pitch will increase engine rpm by about 400 revolutions."
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post #6 of 11 (permalink) Old 09-19-2012, 03:10 PM
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Re: kicker motor prop pitch?

Have you played with adjusting the trim/tilt to see if you can get more out of what you currently have? One notch in or out will make a major difference. On my boat were talkin 2000rpm and a major difference in ride. I trimmed mine out because the hole shot was terrible anyhow and I enjoy it much more.

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post #7 of 11 (permalink) Old 09-19-2012, 03:23 PM Thread Starter
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Re: kicker motor prop pitch?

Yeah, I run it on a garelick kicker mount and have all kind of trim I can adjust on it. Have tried it trimmed up and down, tilted up and down, just not pushing a load well.
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post #8 of 11 (permalink) Old 09-19-2012, 03:35 PM
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Re: kicker motor prop pitch?

what about blades, would not a 4 blade help out more instead of a 3 or 2 blade, dont know just asking,
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post #9 of 11 (permalink) Old 09-23-2012, 10:39 AM
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Re: kicker motor prop pitch?

Keep on, one thing I would caution you about is that the quote may only apply to larger hp motors. Not sure if it still applies to smaller motors. Would hate for you to drop a bunch of pitch and find out that you went too far in the opposite direction. One thing I always do is to check out eBay. Might be able to find a prop a bit cheaper than new. I found one a few years ago for my old Merc, 14.25" x 23p and got it for $50 and change to my door. Would've had to spend well over $200 new.

As for the number of blades... You are just adding additional blades, most times you still have to drop the pitch to make it work right. More bite = less RPM's Pitching a motor is more of an art then a science. Every brand performs different, even at the same diameter and pitch. I've heard of guys that go through 5-6 props before they find the perfect one for their boat/motor combination.

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post #10 of 11 (permalink) Old 09-23-2012, 04:43 PM
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Re: kicker motor prop pitch?

trapjaw, just asking here, a thought a 4 blade was supposed to give stronger hole shot, and power a boat with more energy. and 3 blades and 2 was for top end speed,
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