Prop Swap opinions...

Swedefj40 · Sunday at 6:12 PM

I've been thinking about repropping for a few years now for a better hole shot, better grip in rough seas, & improve fuel economy. Sacrificing top speed if needed.

I rarely run full throttle which seems to be 4500 RPM (rated for 4400 - 4800 rpm) and cruise around 3900 - 4000 rpm @ 26 - 28 mph. It'll come off of step around 3600 rpm. I do a lot of offshore (saltwater) fishing and overnighting on the boat with a couple other people and so she gets pretty loaded down with gear, etc.

My boat is a 1996 22' Campion fiberglass cabin cruiser with a 4.3LX (carbed) 180HP V-6 with a A1 G2 181:1 drive. Prop is an OEM 14-1/2" X 19P aluminium prop (48-832830-C1-19). She's about 3400 lbs dry.

Solas makes a 4 blade Stainless Steel 14-1/4" x 17P prop that I'm thinking would be the right one for my application. It has a slightly smaller diameter (1/4") and a 2" lower pitch. Any thoughts on my choice?

Scott Danforth · Sunday at 6:33 PM

Prop for your normal load (heavy). That will be under propped for running light

jimmbo · Sunday at 7:02 PM

Swedefj40 said:
I've been thinking about repropping for a few years now for a better hole shot, better grip in rough seas, & improve fuel economy. Sacrificing top speed if needed.

I rarely run full throttle which seems to be 4500 RPM (rated for 4400 - 4800 rpm) and cruise around 3900 - 4000 rpm @ 26 - 28 mph. It'll come off of step around 3600 rpm. I do a lot of offshore (saltwater) fishing and overnighting on the boat with a couple other people and so she gets pretty loaded down with gear, etc.

Is that 4500rpm, fully loaded or lightly loaded? A 22ft is asking a lot of a 4.3, even a 5 liter. Even if you underprop it noticeably, the Hole Shot is still gonna be less than neck snapping.
To me you are already close to being over propped and a 3 blade 17 might be a better choice, that will put at or just above the 4800 range. As for a 4 Blade, a 1/4" reduction in Dia is insignificant, and the 4th Blade will load the engine up even more, a drop to 15" might be needed. Hopefully you will be able to maintain being on plane at 4000rpm

Swedefj40 · Sunday at 7:32 PM

jimmbo said:
Is that 4500rpm, fully loaded or lightly loaded? A 22ft is asking a lot of a 4.3, even a 5 liter. Even if you underprop it noticeably, the Hole Shot is still gonna be less than neck snapping.
To me you are already close to being over propped and a 3 blade 17 might be a better choice, that will put at or just above the 4800 range. As for a 4 Blade, a 1/4" reduction in Dia is insignificant, and the 4th Blade will load the engine up even more, a drop to 15" might be needed. Hopefully you will be able to maintain being on plane at 4000rpm

4500 rpm loaded. FYI, the boat had the largest I/O engine option when it was built. Other options were the merc 3.0 4cyl, and a small diesel. Also there was an outboard bracket option up to 200HP. The boat isn't a dog but I just want to see if I can improve things.

Swedefj40 · Sunday at 7:33 PM

Pmt133 · Monday at 4:59 AM

Only thing I can add is make sure sure the tach is accurate before doing anything.

Stinnett21 · Monday at 5:54 AM

If you start changing prop families, brands, number of blades, etc. things get experimental. As you stand right now you are queued up just right to drop 2" pitch with the exact same prop and achieve what you want. Assuming you are currently running a Mercury Black Max I would buy the same thing in a 17" pitch.

jlh3rd · Monday at 6:56 AM

agree with stinnet.
but, your thinking on the 4 blade stainless doesn't seem wrong, but it's still a guess. Mathematically and on paper it works....🫤
Just gets expensive when guessing if it doesn't do what you want and you can't return that stainless prop.

Scott06 · Monday at 7:16 AM

Swedefj40 said:
I've been thinking about repropping for a few years now for a better hole shot, better grip in rough seas, & improve fuel economy. Sacrificing top speed if needed.

I rarely run full throttle which seems to be 4500 RPM (rated for 4400 - 4800 rpm) and cruise around 3900 - 4000 rpm @ 26 - 28 mph. It'll come off of step around 3600 rpm. I do a lot of offshore (saltwater) fishing and overnighting on the boat with a couple other people and so she gets pretty loaded down with gear, etc.

My boat is a 1996 22' Campion fiberglass cabin cruiser with a 4.3LX (carbed) 180HP V-6 with a A1 G2 181:1 drive. Prop is an OEM 14-1/2" X 19P aluminium prop (48-832830-C1-19). She's about 3400 lbs dry.

Solas makes a 4 blade Stainless Steel 14-1/4" x 17P prop that I'm thinking would be the right one for my application. It has a slightly smaller diameter (1/4") and a 2" lower pitch. Any thoughts on my choice?

yes the 17" 4 blade will be a good one to try. Might also get some stern lift and lower planning speed.

In my experience what you give up in tops speed with a 4 blade is more than worth it for what improvements you get over the rpm range where you use your boat most often. Either way I would shot for 4800 rpm or just a tad over at WOT, you will have better throttle response over the entire range this way.

Swedefj40 · Monday at 7:28 AM

Pmt133 said:
Only thing I can add is make sure sure the tach is accurate before doing anything.

I was thinking the same... it's off by 75 rpm or so at idle compared to my timing light but I've never checked at speed.

Swedefj40 · Monday at 7:47 AM

Well I bit the bullet and picked up a slightly used Solas Rubex HR4 14-1/4" x 17" 4 blade Stainless Prop (with merc hub). Guy bought it last month to try on his welded aluminium boat with a 115hp merc, but it was too much prop for him. Got it for less than half of what it costs new so his loss my gain I guess.

So just curious... would anyone know if I would get a more accurate RPM reading if I read from my MFD (Lowrance Elite FS9) through nmea200 converter or the analog tach?

Pmt133 · Monday at 8:04 AM

The nmea signal if available should be about as accurate as you can get.

Swedefj40 · Monday at 8:14 AM

Pmt133 said:
The nmea signal if available should be about as accurate as you can get.

My other option would be to hook up my timing light which is a pain to read while at speed for obvious reasons

Pmt133 · Monday at 8:53 AM

Swedefj40 said:
My other option would be to hook up my timing light which is a pain to read while at speed for obvious reasons

If your tach is adjustable you could cruise at a more leisurely rate with 2 people, get the difference and then adjust the tach. My timing light was long enough to leave behind the driver seat so all I had to do was turn around and look at it. Or just compare values at 2k rpm. Mine didn't seem to drift much beyond that and that can be done in neutral.

Swedefj40 · Monday at 9:01 AM

Pmt133 said:
If your tach is adjustable you could cruise at a more leisurely rate with 2 people, get the difference and then adjust the tach. My timing light was long enough to leave behind the driver seat so all I had to do was turn around and look at it. Or just compare values at 2k rpm. Mine didn't seem to drift much beyond that and that can be done in neutral.

No, it's not adjustable, it just has the cylinder switch at the back. I guess I could hook up the light and then set up my GoPro and watch it through the app. Thanks for the suggestion.

Scott06 · Monday at 9:40 AM

Swedefj40 said:
No, it's not adjustable, it just has the cylinder switch at the back. I guess I could hook up the light and then set up my GoPro and watch it through the app. Thanks for the suggestion.

I would use the timing light at rest to verify what you tach reads vs it rather set it up to read while running. Just rev to 3500 in neutral and compare maybe go up towards redline see how far they are off if at all.

jlh3rd · Monday at 10:30 AM

..see who wins

..have some fun
I'm gonna guess, using all the stuff, mathematics, opinions, etc, out there, that you will see 4800 rpm@WOT....assuming you're fair by running at the exact conditions with the old prop and tach.
2" pitch reduction = 400 rpm gain
One extra blade = 100 rpm reduction
1/4 " less diameter = 50 rpm increase
stainless compared to aluminum....no deflection...50 rpm decrease
net = 300 rpm gain...4800rpm's

let us know.

Jimwhall · Monday at 11:55 AM

Swedefj40 said:
I've been thinking about repropping for a few years now for a better hole shot, better grip in rough seas, & improve fuel economy. Sacrificing top speed if needed.

I rarely run full throttle which seems to be 4500 RPM (rated for 4400 - 4800 rpm) and cruise around 3900 - 4000 rpm @ 26 - 28 mph. It'll come off of step around 3600 rpm. I do a lot of offshore (saltwater) fishing and overnighting on the boat with a couple other people and so she gets pretty loaded down with gear, etc.

My boat is a 1996 22' Campion fiberglass cabin cruiser with a 4.3LX (carbed) 180HP V-6 with a A1 G2 181:1 drive. Prop is an OEM 14-1/2" X 19P aluminium prop (48-832830-C1-19). She's about 3400 lbs dry.

Solas makes a 4 blade Stainless Steel 14-1/4" x 17P prop that I'm thinking would be the right one for my application. It has a slightly smaller diameter (1/4") and a 2" lower pitch. Any thoughts on my choice?

I also went to smart tabs as well as reduced pitch on my prop for my boats.. I do a ton of tubing and water sports with my son and his buddies, and as they've gone from 10 to 18 the hole shot got noticeably worse.

The smart tabs have helped quite a bit with hole shot, and I got a huge improvement when I went to a lower pitch 4 blade plus the smart tabs.

With a boat that size I'd give it the most help you can. I'm not sure if the 4.3 carb has the rev limiter, but if so that takes a load off when it comes to reducing pitch.

Swedefj40 · Monday at 12:56 PM

Jimwhall said:
I also went to smart tabs as well as reduced pitch on my prop for my boats.. I do a ton of tubing and water sports with my son and his buddies, and as they've gone from 10 to 18 the hole shot got noticeably worse.

The smart tabs have helped quite a bit with hole shot, and I got a huge improvement when I went to a lower pitch 4 blade plus the smart tabs.

With a boat that size I'd give it the most help you can. I'm not sure if the 4.3 carb has the rev limiter, but if so that takes a load off when it comes to reducing pitch.

No limiter that I know of. Smart tabs would be nice, but maybe later though.

Jimwhall · Monday at 1:07 PM

Swedefj40 said:
No limiter that I know of. Smart tabs would be nice, but maybe later though.

FWIW I got mine with a 21p 3 blade. She'd hit 50 easy with just my wife and I, but didn't tube well.

I dropped to an aluminum 4 blade 19, but still had problems fully loaded and the more I used it the more often I'd have 6-7 people on it. I then dropped to a 17 four blade aluminum and that was much better.

Going to the 17 4 blade SS plus the trim tabs made a huge difference. My top speed is only around 46 or so, but that's plenty for me TBH. The extra stern lift was worth all the money.

I do have an MFI 4.3 and a smaller boat though.

One thing to check is that Turning Point used to have a prop exchange program that I used a couple of times. That made life *MUCH* easier for me so I didn't have to keep buying new props. I bought the 19 and exchanged it for the 17.

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