Prop selection help

[bfish]

I have a 16.5 ft riveted v-hull with 25 hp tiller (plated max of 45 hp for tiller but sc version has 75 hp rating).

Current prop did work okay, although pretty chewed up, it was a 3-blade, 12 pitch.

I have a SenDec tach (and hour meter) on the way. I have no clue what existing rpms were but I was okay with the minimum speed (trolling speed) of 1.5 mph and top end (25.5 mph) when solo (which is most of the time).

Current prop is now, umm, well, not so use-able as it is missing a 2 inch chuck from one of the fins.

I use this boat mainly to troll with, so I am thinking that a 4-blade prop would give a little more slow speed control, right? I don't want the minimum speed to increase at all, a slight decrease would be okay. Also since this is a pretty light boat (550 lbs), I should not expect too much drop in top end (2-3 mph, right?). 4-blade prop is only $15 more than 3-blade (both aluminum).

Should I drop down to 11-pitch with the 4-blade?

Or should I stick with a 3-blade and move up to 13 or 14 pitch (assuming I won't hit the rev limiter) to maximize top end (I assume that trolling speed won't be affected due to lots of prop slip at slow speed with the 3-blade, right?).

Any other suggestions? As I am all ears.

[tkwalker]

Originally Posted by bfish

I have a 16.5 ft riveted v-hull with 25 hp tiller (plated max of 45 hp for tiller but sc version has 75 hp rating).

Current prop did work okay, although pretty chewed up, it was a 3-blade, 12 pitch.

I have a SenDec tach (and hour meter) on the way. I have no clue what existing rpms were but I was okay with the minimum speed (trolling speed) of 1.5 mph and top end (25.5 mph) when solo (which is most of the time).

Current prop is now, umm, well, not so use-able as it is missing a 2 inch chuck from one of the fins.

I use this boat mainly to troll with, so I am thinking that a 4-blade prop would give a little more slow speed control, right? I don't want the minimum speed to increase at all, a slight decrease would be okay. Also since this is a pretty light boat (550 lbs), I should not expect too much drop in top end (2-3 mph, right?). 4-blade prop is only $15 more than 3-blade (both aluminum).

Should I drop down to 11-pitch with the 4-blade?

Or should I stick with a 3-blade and move up to 13 or 14 pitch (assuming I won't hit the rev limiter) to maximize top end (I assume that trolling speed won't be affected due to lots of prop slip at slow speed with the 3-blade, right?).

Any other suggestions? As I am all ears.

bfish, you don't need a 4 blade ... What brand of outboard do you have that has a rev-limiter? is it a 4 stroke ? I haven't worked on any real late models yet ... So I am Curious ... There is no prop slip at slow speed with any good prop unless you have a worn out hub ...( guess you are thinking about blade bit) My suggestion ... Take you existing prop to Performance Propeller in Old Hickory... Have them fix it and have it cupped for optimum performance ... But talk to them they can do things with props ... But lets face it ... This is a fishing rig, with an Aluminum prop which flex ... This is not a high performance motor with a Stainless prop ...

Now this is how pitching works ... At the top of the power curve of your motor and other weight factors, boat type etc ... For ever revolution of the prop the boat moves forward that pitch dimension ... For instance you have a 12 pitch ... theoretically you should move forward 12 inches .. times the rev's ...

The higher the pitch top end speed increases to a point ... but you may sacrifice the bottom end ... In another words the prop will not bite the water coming out of the hole it will spin ...

My suggestion Keep the prop stock ... The Mfr's know what an all round prop should be for their motors ... Think about a troll plate if you want to drop your speed ... Hope this helps ... <'TK><

[bfish]

Old Hickory is over 2.5 hours away, the closest prop shop that allows testing is about 1.5 hr away.

'96 Honda (4-stroke). Stock prop was a 9.25 dia, 12 pitch. Replacement props are all 10-10.5 dia. I am not sure what diameter is on there now (boat is not kept here at the house); I just know it is a 12 pitch and that I was fine with low end speed (but not handling) and the top end was okay too. However top end, felt like the last couple mph were really slow to develop (ie liked to fast cruise at 21 mph but WOT was 25 with dinged up prop). In other words the last couple of rpms didn't seem to add much speed. That prop is a no go now (ie missing a 2" chunk) so I can't even test for rpm range now.

I am not trying to go any slower, although I would rather not go any faster at idle/troll. Boat came with troll plate; hard to steer at low speeds with that thing choking it down. In heavy winds (even with plate removed), slow trolling can be tough to maintain direction (ie boat gets pushed around by the wind, even though going at 1.5-2.0 mph). For that reason I though a 4-blade would work better, although I have concerns that top end speed may suffer some (in which I am ok with 2-3 mph but not 5 mph). Although I thought it could be mitigated some buy going with larger diameter.

Stock prop, I figure, would be in the middle of performance range. Boat and motor were not a package deal so it isn't "matched". Seems to me that there should be room to tweak both the low and high end performance, especially if I am increasing diameter.

[tkwalker]

bfish I am going to email this thread to my partner who is a retired boat racer, motor builder and prop expert ... let's see what he thinks .... <'TK><

[tkwalker]

Originally Posted by tkwalker

bfish I am going to email this thread to my partner who is a retired boat racer, motor builder and prop expert ... let's see what he thinks .... <'TK><

Bfish, I sent this thread to Sam This was His reply to me .... <'TK><

He definitely doesn't need a 4 blade prop I don't feel like he would see any performance improvement. It sounds like if any thing he may need to go down in pitch rather than up to achieve maximum performance. He says that the last few rpm's and mph are slow to come which would indicate too much pitch. I would suggest dropping down to a 10 or 10.5 pitch prop especially since he says the replacement props are all 10/10.5 diameter. We need to check what props Solas has available for his motor and see if they might offer a better solution I think the added diameter would kill his rpm's.

[bfish]

Thanks TK

[Pookie]

My bass rigs have always had SS props. In the last 20 years, all of my duck boats have had SS props. You are simply wasting your time running an aluminum prop.

TK gave you good advice about Performance Propellar. James has forgotten more about propellars than any 10 of us together ever knew. He can fix your aluminum prop, regardless of the condition, but will readily tell you the same as I have about running a stainless prop.