4-Blade Prop on 17' Checkmate

[11YearItch]

The stern of my Checkmate Spectra 171 with its 500 lb. 150hp V6 Evinrude outboard and a tank full of gas (21 gallons) sits very low in the water. The boat has power trim, automatic Nauticus trim tabs, no jack plate, and a Michigan Wheel 14.5 x 19 aluminum 3-blade prop. At WOT (5000 rpm) the boat runs about 43 - 45 mph. Since the prop is a little beat up I am considering replacing it with a Michigan Wheel or Solas Amita 4-blade prop. The reports I have read say that four blade props often provide more stern lift, work well for pulling skiers, run smoother, and get slightly better fuel economy at mid-range rpm. These are benefits I would like, however, I have also read that these benefits are not as noticeable on boats under 24 feet. Since my boat is only 17 feet I am not sure I want to spend the money for a 4-blade prop and then be disappointed with its performance. So, now I would like to see comments from anyone that has been down this road.

 

[sim]

As the owner or former owner of several boats in the sub-24 foot range I am a huge fan of 4 blades over 3. Better EVERYTHING except top end which can sometimes suffer by a (very) few mph.
The boat that it made the biggest difference in was my 16.5 foot Predictor with a 115 Merc on which I had a Powertec RXB4. Much better holeshot, handling and stability than a 3 blade.
On my 23 foot Enforcer with a heavy I/O I don't even like riding a 3 blade-it feels squirrely on the top end and takes forever to come on plane. With the 4 blade it pops right out and rides like a Caddy at speed.

 

[wired]

Ive used quite a few of the Solas Titan 4 props. Great hole shot, mid range and top end. I absolutely recommend them. Take their pitch number with a grain of salt though. A 17 pitch Titan 4 will put you well into the mid 50's and a 19 pitch into the 60's.

 

[11YearItch]

As the owner or former owner of several boats in the sub-24 foot range I am a huge fan of 4 blades over 3. Better EVERYTHING except top end which can sometimes suffer by a (very) few mph.
The boat that it made the biggest difference in was my 16.5 foot Predictor with a 115 Merc on which I had a Powertec RXB4. Much better holeshot, handling and stability than a 3 blade.
On my 23 foot Enforcer with a heavy I/O I don't even like riding a 3 blade-it feels squirrely on the top end and takes forever to come on plane. With the 4 blade it pops right out and rides like a Caddy at speed.

Thanks sim for your good 4-blade input. I am not really concerned about loosing a few mph at top end so am leaning toward buying a 4-blade prop. If I do decide the 4-blade is the way to go the next set of decisions will be aluminum vs stainless steel, what diameter & pitch, and what manufacturer.

 

[11YearItch]

Ive used quite a few of the Solas Titan 4 props. Great hole shot, mid range and top end. I absolutely recommend them. Take their pitch number with a grain of salt though. A 17 pitch Titan 4 will put you well into the mid 50's and a 19 pitch into the 60's.

Thanks wired for your advice about Solas Titan pitch numbers. Since my existing 3-blade prop is a 19 pitch I probably would go with a 17 pitch 4-blade. If a Solas Titan 17 pitch can get me more stern lift and also put me into the mid 50's that would be great.

 

[wired]

I was able to turn a 17 pitch Solas Titan 4 to 57 MPH at 6000 RPM with a 2:1 lower. By all the prop slip calculators that is physically impossible. That's why I say take their published pitch numbers with a grain of salt. They might be efficient but they can't be THAT efficient. Probably more like a 19. Great holeshot and cruise too.

 

[Checker7]

I have same boat, Spectra 17 but with 150 Merc XR4, run a 22 pitch 3 blade stainless Merc Laser II prop, and I just saw 55 GPS at around 5500 with two people and full of camping gear, coolers, etc.

That's also with the motor probably too low, the prop shaft is more than 5" below the bottom of the hull pad. (Or bottom of hull to top inside of motor clamp is 22").


(BTW, I don't think your motor wieghs 150 lbs, I just looked up late 80's Johnson/Evinrude 150's and all are under 400, like the XR4 Merc.)

 

[11YearItch]

I have same boat, Spectra 17 but with 150 Merc XR4, run a 22 pitch 3 blade stainless Merc Laser II prop, and I just saw 55 GPS at around 5500 with two people and full of camping gear, coolers, etc.

That's also with the motor probably too low, the prop shaft is more than 5" below the bottom of the hull pad. (Or bottom of hull to top inside of motor clamp is 22").


(BTW, I don't think your motor wieghs 150 lbs, I just looked up late 80's Johnson/Evinrude 150's and all are under 400, like the XR4 Merc.)

It looks like Spring is here to stay so today I took the winter covering off my Spectra 17 and started up the engine, etc. While doing so I measured the engine height. My measurements came out the same as yours, i.e. 5" and 22".

Last summer I was getting about 40 to 41 MPH at 5000 RPM after installing a 14.5 X 18 Michigan Wheel 4 blade aluminum prop. My boat now seems to run much smoother at low speeds and comes up out of the hole faster than it did with the 14.5 X 19 Michigan Wheel that I replaced. Since I am not overly interested in top end speed I am satisfied with the 4 blade prop.