prop talk

[spring fever]

I have a 115 hp merc command thrust with a Black max 832828 A45 17P prop- 3 blade aluminum- this is on a 17ft CC with a 9.9 merc kicker. Prop seems the right size-hits 6200 rpm and does 35- The boat is a little stern heavy-although because of the power it does jump up on the step pretty smartly. Does anyone have an opinion on what a 4 blade stainless would do for me-do I keep the same pitch? Is it a waste of money.

 

[ship happens]

If it's a command thrust must be a 25inch running a V6 case with the 115 gear ratio if I'm correct?

6200 is alot. Same pitch 4 blade I think will work great for you. 14.25 x 17

 

[spring fever]

If it's a command thrust must be a 25inch running a V6 case with the 115 gear ratio if I'm correct?

6200 is alot. Same pitch 4 blade I think will work great for you. 14.25 x 17

Yes you are correct it is a 25 inch C Thrust 2.38 x 1 gear case. Aluminum prop- 3 blade-will I notice a difference if I switch to a SS 4 blade or is this a waste of money. I am a jigger and I was hoping this might lift the stern a bit while I am looking for bait at around 10 mph

 

[ship happens]

Absolutely would if you have the power, which sure sounds like you have plenty of headroom. Sternlift check, low speed travel check, better midrange performance check.

 

[Coyote Spooner]

I’ve been trying to find the right prop, for my boat, for a couple years. My tach was part of the problem. Vessel View Mobile helped show me that. There isn’t very many prop shops around anymore. Especially in the lower mainland. I ended up phoning Olympic Propeller in Anacortes. They also have a website called “Get a Prop”. They have a prop expert called “The Proptologist”. I believe he takes calls in the mornings. He helped guide me on what to buy. I was learning towards and expensive 4 blade stainless, and he steered me towards a less expensive aluminun, which was cheaper from Victoria propeller. Yours may benefit from a 4 blade stainless ? But it’s good to get a second or third opinion. Just an option before pulling the trigger on a new wheel.

 

[ship happens]

If you compare a stainless wheel vs an aluminum it's not even a comparison. 4 blades are completely different for outboards. They have a smaller diameter and another blade for one. Second they are designed different, with different rake, and different cupping from one type to the next. I wpuld look at the solas 4 blade if it was my choice.

 

[baddogg]

Interesting topic. I have a 115 HP Mercery Command Thrust Pro XS as well on a 98 Campion 542. I have no issues with the prop that I have but perhaps there is a better option for me. Running a Black Max 14-1/2/2X19 RH AL according to my invoice. Not knowing much about props I'm not even sure what this is.

 

[ship happens]

Just keep in mind that anything I have suggested with @spring fever in this thread is because he asked the right questions, and gave the correct details with his boat and current prop pitch and what he expects, wants, and not to forget his current WOT

 

[Aquaholic]

Aluminum opinion, not stainless.

6200 is over revving a bit at WOT. No wonder it does jump on step pretty smartly. Mercury says pitch for pitch when going from the correct 3 blade to their Spitfire 4 blade. Their prop selector online is close. Bridgeview does allow exchange if it comes back unharmed, but your specs suggest a 19” if you want less rpm.

4 blade 17” you’d like if you're ok with slight over revving based on your data. Solas is less money but I noticed a bit better low speed handling and especially backing up and full lock reaction with the Spitfire over the Solas. (both 4 blade on a non CT Merc engine)

I lost a bit of mph but rpm was almost identical (5950-6000) when I went 3 to 4 blade. Lower planing rpm and aforementioned drive ability was a huge plus.

 

[Bifmalibu]

I've got about 5 or 6 outings on my new Solas Rubex 4 blade. Night and day improvement from the 3 blade BK from Vic prop. Everything improved with the 4 blade, low speed handling around the dock, hole shot, top speed/rpm(34.9mph at 5600 rpm with a 90hp on a 17' Arima. Two batteries, kicker and fuel tank at the stern. Best 200 bucks I ever spent. I'm completely satisfied with this propellor but I can't shake the thought of how a stainless would perform.

 

[Sharphooks]

A couple of boats ago, I put a 4 blade PowerTech on my single DF300 Suzuki which was hung on a 24 Skagit Orca. It seemed to have a better hole shot, never broke loose in rough water etc etc. Generally a good re-prop experience. But one day I hit a rock in Central Coast and put the older 3 blade back on....it blew my mind when I saw a 9% INCREASE in fuel efficiency with the 3 blade

Mind you that 4 blade was a huge prop: 16” x 17P stainless....heavy!

I’ve been thinking of going to 4 blades on the twin DF300’s on my latest boat for better stern lift but that experience with a drop in fuel efficiency spooks me. I’m already dealing with big fuel burn on that boat

Not trying to derail the thread but I get the feeling that the design and weight of the boat is an important factor as to the relative outcome you achieve when making the switch from a 3 blade to a 4 blade

Case in point: yesterday I discussed 3 blades and 4 blades with the head dude at Seasport....this guy has years of experience building these boats, hanging power on the transoms, propping the outboards, then test driving them.

His comment: he has seen almost zero tangible benefits of going from a 3 blade to a 4 blade ... lots of different boats—-Orcas, Seasports, C-sports etc ——that blew my mind as it flies in the face of everything I read on this site and Hull Truth etc etc

So the upshot seems to be: your results will vary depending on what you’re driving

I’d be interested to hear your comments, Ship Hap.....

 

[ship happens]

A couple of boats ago, I put a 4 blade PowerTech on my single DF300 Suzuki which was hung on a 24 Skagit Orca. It seemed to have a better hole shot, never broke loose in rough water etc etc. Generally a good re-prop experience. But one day I hit a rock in Central Coast and put the older 3 blade back on....it blew my mind when I saw a 9% INCREASE in fuel efficiency with the 3 blade

Mind you that 4 blade was a huge prop: 16” x 17P stainless....heavy!

I’ve been thinking of going to 4 blades on the twin DF300’s on my latest boat for better stern lift but that experience with a drop in fuel efficiency spooks me. I’m already dealing with big fuel burn on that boat

Not trying to derail the thread but I get the feeling that the design and weight of the boat is an important factor as to the relative outcome you achieve when making the switch from a 3 blade to a 4 blade

Case in point: yesterday I discussed 3 blades and 4 blades with the head dude at Seasport....this guy has years of experience building these boats, hanging power on the transoms, propping the outboards, then test driving them.

His comment: he has seen almost zero tangible benefits of going from a 3 blade to a 4 blade ... lots of different boats—-Orcas, Seasports, C-sports etc ——that blew my mind as it flies in the face of everything I read on this site and Hull Truth etc etc

So the upshot seems to be: your results will vary depending on what you’re driving

I’d be interested to hear your comments, Ship Hap.....

Yeah I can't comment much on propping DF300s. They have ability to swing larger diameter props. Hopefully soon Most outboards cannot mount that diameter because there's not enough room between the propshaft and the cavitation plate. I don't know what their gear ratio is but it must play a part in that as well. In your case maybe it's exactly the reason that you didn't gain efficiency. That's alot of surface area. There's also a ton of OEM and aftermarket props out there that all have different characteristics.

I'm not sure why the guy at seasport would say that. There huge tangible differences in alot of applications. Some boats needs that bow lift so some boats like 3 blades. Not sure why someone could say that. Different apllications call for different things..

Generally speaking 3 blade props have a different rake then 4 blades. That is basically what determines bow lifing or stern lifting

 

[Sharphooks]

Thanks for your comments, Ship. No doubt a 4 blade in most applications produces stern lift due to the extra blade surface area. I‘m thinking that the SeaSport guy said that because he was looking at the full spectrum of pros and cons between 3 blades and 4 blades when calculating net benefit. So maybe you get increased stern lift with a 4 blade but you lose top end speed etc ...maybe the net result of compromises just didn’t add up for him on the boats he put 4 blades on—-he mentioned they all went back to 3 blades and after tweaking the pitch until they found the right one for the owner’s preffered boating behavior, called it good

Didn’t mean to derail your thread, Spring Fever. Sorry!

 

[SpringFever552]

Turning Point Hustler 4 blade aluminum,
Stainless waste of $$
Thank me later

 

[spring fever]

I have a 115 hp merc command thrust with a Black max 832828 A45 17P prop- 3 blade aluminum- this is on a 17ft CC with a 9.9 merc kicker. Prop seems the right size-hits 6200 rpm and does 35- The boat is a little stern heavy-although because of the power it does jump up on the step pretty smartly. Does anyone have an opinion on what a 4 blade stainless would do for me-do I keep the same pitch? Is it a waste of money.

Sooo-talked to north island prop and he gave me a used reworked 14.3 X19 P 4 blade alum-used it twice-I can take it back but after using it for jigging I am satisfied-there is room to move but I am happy--I think. Top rpm was 5500 vs 6000--my usual cruise is 4200 giving 26.5 -4 blade gives 3900 for 26.5
Better hole shot and very fast to plane-seems less stern heavy at the 8 to 10 mph range--feels smoother. By the way he looked at my 3 blade and what I thought was cavitation marks-the prop was bent-I had hit a small log-who knew-no other indication except worn off paint in the cups of the blade. Not the total fix I hoped for but as good as I feel I want to chase. Gives' me a spare prop plus improved performance for very little money plus a straight 3 blade.