PROPS

[mrmacey]

im sitting here considering the thought of a new prop i only have the one i need a back up as im reading about this i see that if you change the pitch it could change the rpms is this a good way to go to slow boat down for trolling or is the rpms,pitch, only for crusing speeds,is there a preference on aluminum or stainless, clamdigger you should have input on this seeing you change yours alot during the season!!

[JohnR]

What do you have for an engine in your boat?

I personally wouldn't o nuts. A properly spec'ed Stainless Steel prop will set you back a few hundred and might eek out a couple more miles per our but that first rock you hit, the blades might not give way, and you could damage your lower end. An aluminum prop will likely sheer a blade before damaging the lower end.

Clammer's different. He uses Magnetic props and fishes around a lot of iron ore

[mrmacey]

merc i/o 3.0 135hp im very happy with this 4 cyl top end 35mph very economical on gas im more interested in slowing it down for trolling was wondering if im getting spare prop anyway if i should change anything!! as to getting it up on rocks only by accident! never on purpose i got rods that will cast in there and if i did get up in there which i have! i think i would drift it and use my oar to get back out if i could, only once last summer did i get on rocks and that was by accident drifting

[JohnR]

Save the money & just get aluminum if you need a backup... There are composite ones too. If you are topping out at 35 now, and it's rigged right, a SS prop isn't going to help trememndously.

And you can always look at ways of creating extra drag on the boat to slow the troll down.

[mikecc]

If that is the newer style motor in the past 2 years they have come out with a chip or fix to slow the motor down. my buddy got it and he now loves the setup.
he could never slow the boat down enough to trool tube and worms.with the fix he is in the strike zone again

[Billybob]

I don't think you're gonna do much to your trolling speed by repitching.Lets say you're lowest trolling speed is at idle speed, you can only pitch down 2 maybe 4 inches, at those low rpm's the difference will be minimal, but at cruise or w.o.t., it will be significant, and you won't like it, and you'll have to keep an eye on your rpm's so it doesn't run away on you.You're best bet is to get your idle down as low as you can I'm thinking 800 or lower if you can. You're really best off propping properly, which means that you're rpms at w.o.t should be at spec.I used to have that setup and if you're just looking for a spare emergency prop, I may have something left in the garage with a ding or 2 and you could have it.What are you swinging now?

[Clammer]

YO =iron ore ==thats what the bass are feeding on =====
If your not smashing up props, your not where the fish are//////////////excluding TROLLING< chunking , etc
you should be able to cast up onto the shore, thats hao close tooooooooooooooooo go ,and on a good day put the boat on the rocks also!!!!!!!!!!! sand doesn,t count//////////

[Duke41]

If I get you right, it sounds like you want to slow your boat down for trolling. I use a 5 gallon bucket hung off the stern. Use two lines and center it behind your motor. Don't forget to remove it before you take off. Another trick I use is to put the boat into neutral as I go over a hump or boulder field. Slowing the boat down will keep the baits in front of the fat lazy old stripers we all want to catch. Then pop her back into gear until I hit the next structure.

[Van]

I agree with these posts. keep the prop that is spec'd for your engine and boat combo. You want the rpm to be within the manufacturers range. If you lose top end, you will hate it, and you will be over revving the power. If you pitch higher you will increase overall speed at all rpms, but you'll kill the power.

It sounds like you have a good speed for that power and boat size, stick with it.

As john said, you can go with aluminum which may save your prop shaft if you hit anything. Maybe an aluminum spare is the way to go for you. They are muych cheaper.

I use SS and did bend the shaft a few years ago.
But I still prefer SS.

To slow the boat down----drag something---or someone !!!!!

[Mr. Sandman]

ooh ooh... Having done some work on propeller hydrodynamics...(mainly for ships but the same principals applies) and having done a little work with some the merc marine race guys developing an integrated propulsion system/hull a few years back... let me add my 2 cents.

Small boat prop selection is sort of a trial and error game IMO. Most boat manufactures don't do the necessary model (or full scale) testing do obtain the info needed for ideal prop selection. So what they do in most cases is try off the shelf props that are in the ballpark and see which one seems to be good enough without blowing the engine at wide open. There is actually a lot to it but since cost is the driving issue, pick one off the shelf and ship it! is the motto.
You might say...how much would I gain if we had the perfect prop. You might do 10% better if you are lucky. To some that is a lot, to some...not. So off the shelf picks are the rule for pleasure boaters. Ships and competitive racing is another story.

Anyway, you generally should pick the best prop (near peak eff.) at the design speed of the boat/engine, not at troll. If you decide you want a slower toll speed and you put a prop on that gives you that (reduce the pitch), you will over-rev the engine at high speeds. For most boaters, they think the "perfect" prop is one that lets the engine run at red line at wide-open throttle and they live with the performance at all other ranges. The hard thing about propellers is you only have one pitch (or pitch distribution)and that is only ideal at one advance ratio (inflow speed in essence) BUT you have a *range* of operational conditions, no single pitch and be ideal at all rpms and load. (That is why some ships have controllable pitch props..To match the pitch to the condition.

ANYWAY, If you want a slower troll I would leave the prop alone if it were performing OK at other speeds. (The most important speed is the cruise condition)

Can you ...Lower the RPM of the engine at troll?...(It sounds like you have a 4 cycle they are much better at low RPM then 2 cycles and you might be able to adjust the low speed throttle a bit to give you a slower troll)
Also, you might think about creating drag some how...(toss over a sea anchor) Not very elegant but it would slow you down.

If you troll a lot, you might want to consider a cheap trolling motor or (kicker), they can give you a great troll, the prop is so mismatched for the boat that you can creep along.

If you have ever been on some of the newer 50 or 60 footers with big high torque diesels, they tend to troll way too fast because they need to have a big prop to absorb the power...have you ever been on some of these boats when they put them in gear and they lurch forward? A couple of the newer boats I have been on have a cool option...it is called a trolling throttle, it lets the transmission slip at low speeds to essentially let you get any trolling speed you want without touching the main fuel throttle.

Sorry for all the babble, I would try and adjust the low speed throttle and not #^&#^&#^&#^& with the prop first.

[mrmacey]

i am just looking for spare!! i was reading about pitch and was wondering if that slowed you down i dont want to change specs! or fool around with engine idle by the way i dont think on this motor i can change idle anyway but i would like to look into that chip mikes talking about and see if that goes with mine, bill ill look and see if i can find specs on mine im going to guess 14/2 does that make sense thats what i seen in book it says go out and get numbers ill do that later!!! thanks for the offer!! i figure a few more years with this boat maybe trade up bigger or drop 5.0 in there and trade motors but then i pay for gas!!