I have a 21 foot sun tracker fishing barge with a
115 mercury.
My question is i don't seem to have much top end speed I was
Wondering if the prop I have is the wrong pitch for our area
It's a 14 inch 9 pitch max speed of only 18 Mph attached is a
Picture of the numbers on the prop
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Speed of the boat is irrelevant to the pitch that you should be running. What is relevant is the RPM of the engine at WOT (wide open throttle).
A prop is like the final gear of an outboard, it determines resistance to spinning in the water. If the engine reaches it's max recommended RPM at WOT, then the prop is correct. If the engine over-revs, the prop is to short (pitch is a measure of how far a prop will travel in one revolution with no slippage) if the engine will not achieve max RPM the pitch is to long.
Now enter Utah lakes elevations and how that elevation affects engine performance.
The air at Powell is much thicker than the air at the berry because of elevation. This effects the true HP output of the engine. It will develop less HP at higher elevations because of less air pressure, which results in less O2 in the air and less HP being produced.
Now, tell me, what lake were you on when the 18mph occurred and what was the engine RPM at that time?
I had to rework your photo to see the markings and indeed it looks like you have a 14x9 prop. I had no idea that you could get that low of a pitch for that motor. I run a 14x17 on the Berry/Red Fleet other high elevations, a 14x19 on places like Rockport and Willard and a 14x21 on Powell. My target RPM is 5,400 max.
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I fish strawberry and starvation and the flaming gorge my wot
Is 4800
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The pontoon came from Idaho and that was the factory prop on the
Motor it's a 2006 the owner says
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4,800 is in the lower end of the max RPM for that motor. You have the correct prop and are running fine for the altitudes you are at. (4,750 to 5,250, assuming the motor is a 2 stroke) Four strokes run higher RPM, (5,000 to 6,000), if your motor is a 4 stroke, you need to go to an even shorter prop, which will reduce speed even more.
Pontoon boats are not the fastest or most efficient hulls.
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Is the boat flat at that speed/rpm or is the back end squatting in the water? If the boat is squatting you should trim the motor to get the hull as parallel to the water as possible.
If when doing this the boat increases RPM and speed, you have found what is holding you back. Trim.
I am assuming the logs have no water in them...
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That is a crazy low pitch. If it was higher I'd suggest a stainless prop and get rid of the blade flex of an aluminum prop. The world of props is never ending in the bass boat hull crowd. Higher elevations you have to go to the locals and see what they are running. Somebody will chime in with a similar boat...I'll shoot ya pm with a link
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I contacted mercury they said the prop I have was made for use at sea level for the trolling speedso so a kicker wouldn't be needed
They suggested that the best prop for my pontoon would be a 14 inch 13 pitch for our elevation.
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a 110 hp engine is not a lot of power for a boat at high altitude , unless it is super charged, also remember everything you gain on the top speed end you loose on the hole shot or bottom end . 18 mph may seem to slow but my 23 footer has a 310 hp and i can do about 39 mph on the berry so with 3 times the power i'm only going 20 mph faster just food for thought . also the best fishing is below 3mph [
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[font "Comic Sans MS"][#800000]As Troll has already indicated, prop pitch is all about getting your motor to achieve an RPM as close to MAX as possible WITHOUT going over the max. And your max speed will come with the proper trim applied.[/#800000][/font]
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[font "Comic Sans MS"][#800000]As to the prop metal, the problem with stainless steel props is the fact that there is no give to them when the come in contact with something hard, such as rocks. What happens then is something inside the lower unit (i.e., gears a/o shafts) of your motor can, and do, break. The repair/replacement of a lower unit can be 10 times the cost of replacing an aluminum prop. But they do give you slightly better performance than aluminum with all other factors being equal. Let your wallet be your guide on this issue.[/#800000][/font]
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[font "Comic Sans MS"][#800000]For the way I use my boat (16 ft Tracker w/ 75 hp Optimax), aluminum will always be my choice. I just made my first prop replacement a month ago after 11 years of service - $175.[/#800000][/font]
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[font "Comic Sans MS"][#800000]Try the Mercury recommendation of a 14X13 and see where your RPMs fall. That should bring you closer to the max for that motor. Then trim for best speed without cavitating the motor.[/#800000][/font]
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[font "Comic Sans MS"][#800000] "As to the prop metal, the problem with stainless steel props is the fact that there is no give to them when the come in contact with something hard, such as rocks."
[size 3][#000000][font "Arial"]That's not a problem with the prop, that's a problem with the operator. I've seen some terrible damage to lowers with both kinds of props. [/font][/#000000][/size]
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[quote fsh4fun05][font "Comic Sans MS"][#800000] "As to the prop metal, the problem with stainless steel props is the fact that there is no give to them when the come in contact with something hard, such as rocks."
[size 3][#000000][font "Arial"]That's not a problem with the prop, that's a problem with the operator. I've seen some terrible damage to lowers with both kinds of props. [/font][/#000000][/size]
[/#800000][/font][/quote][font "Comic Sans MS"][#800000]We could probably debate that point for a week. Can an aluminum prop hitting an immovable object cause lower unit damage? Of course it can. My advise comes from what the dealership mechanic told me at the time I purchased my boat new. He specifically said it was more likely to damage the lower unit with a steel prop than it was with an aluminum prop. He said nothing about operator error being in the equation. I'm still standing behind my earlier statement based on the advise of a much more knowledgeable person than myself in this regard. You and the OP are free to make your own choices as to which prop you use. As I said, it's your wallet. May you always have tight lines and enjoy fishing as much as I do.[/#800000][/font]
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