Solas prop hieroglyphics for DF70A

[JeffJuneau]

Hi, I have looked at some of the postings here on props that seem to be different than what I have printed between the blades of my Solas prop on my DF70A. I am trying to determine if I have the correct prop for my 2009 Mac 26M. I know many of you have this identical engine. I apologize if I should be able to determine this from some table (that I haven't found yet), but thought the Mac community would probably have the right answer. I can tell that a new prop was installed around 2015 from invoices of the PO, but not the diameter and pitch for sure. I would say that most of my use will be with a medium load on the Mac. Not more than 2-people (under 400 lbs of person load), between 24 and 35 gal of gas, and maybe 300 lbs of gear, including: inflatable, kicker, water, food, electronics, safety, personal stuff.

SOLAS
9411-133-13
RUBEX 4114

Thanks for the umpteenth time for all the help and advice. Jeff

[Jimmyt]

Here is the batman decoder ring...



13-1/4 dia, 13 inch pitch

Could it have been 138-13? They don't show a 9411-133-13 in the catalog. The 138 is a 13.75" dia.

I'm running a 13.75 x 13 on my 60hp Etec. It's close to correct for my application. Seems like you might be a tad under-propped. Do you have a speed vs wide open RPM data point?

Here's the catalog listing FYI:

[JeffJuneau]

Hi Jimmyt, You are right and thanks so much for the info. I checked it again and it is an "8" and not a "3" , so: 9411-138-13. Apologies, the lighting wasn't so great. So, I haven't felt like running my DF70 at WOT yet. Also, there are always some type of tidal current to deal with here, so it is often difficult to get an accurate water speed. My speedometer on chartplotter has never worked right. My engine always seems like it is working so hard to push this big tug around at planing speeds compared with my last boat (a 17.5' aluminum runabout also with an eTec 60). My 26M also has bottom paint, so I when I do the WOT test next spring, I suppose that will be a factor too. So, I think your concluding that my prop is a 13.75 with a 13 pitch? I am just grabbing at straws here, but my eTec 60 had so much more torque than an equivalent 4-stroke, I wonder if it can take the same prop that a 4-stroke 70hp uses? By-the-way, really liked my 2013 eTec, and the weight, size, torque seems perfect for a 26M. Still hoping that enough people on this forum have the DF70 on their 26M so I can get some verification of correct prop size before I put it in the water this spring. Thanks, Jeff

[Jimmyt]

Hi Jimmyt, You are right and thanks so much for the info. I checked it again and it is an "8" and not a "3" , so: <a href="tel:9411-138-13">9411-138-13</a>. Apologies, the lighting wasn't so great. So, I haven't felt like running my DF70 at WOT yet. Also, there are always some type of tidal current to deal with here, so it is often difficult to get an accurate water speed. My speedometer on chartplotter has never worked right. My engine always seems like it is working so hard to push this big tug around at planing speeds compared with my last boat (a 17.5' aluminum runabout also with an eTec 60). My 26M also has bottom paint, so I when I do the WOT test next spring, I suppose that will be a factor too. So, I think your concluding that my prop is a 13.75 with a 13 pitch? I am just grabbing at straws here, but my eTec 60 had so much more torque than an equivalent 4-stroke, I wonder if it can take the same prop that a 4-stroke 70hp uses? By-the-way, really liked my 2013 eTec, and the weight, size, torque seems perfect for a 26M. Still hoping that enough people on this forum have the DF70 on their 26M so I can get some verification of correct prop size before I put it in the water this spring. Thanks, Jeff

I have to have a LOT of light to see my prop stamping. Still hard to tell the 8's from the 3's.

The Mac is a whole different animal from your aluminum runabout as you know. My neighbor has a 70 on his 14 ft whaler. I couldn't believe a 60 could plane my 26M. But it does. It is running in the upper end of the RPM range, but it does it.

If you have fast current, I don't know how useful the speed data will be, unless you have a sensor on the boat. GPS won't be of much value. You should be able to get a WOT RPM, though. That will give you an important data point.

[Russ]

. Still hoping that enough people on this forum have the DF70 on their 26M so I can get some verification of correct prop size before I put it in the water this spring.

I have the DF70 on my 26M loaded heavy like yours. However, I'm in freshwater and at 5,000' elevation. BWY propped it for Salt Water boating and it never got to WOT RPMs, so I lowered the pitch and it's much happier now.

The boat is in storage, next time I go out there I'll look at the 2 props I have. However, I believe your ideal prop might not be the same as mine.

You could call BWY and see what they recommend. They have seen a lot of Macs and props.

[Tomfoolery]

If you have fast current, I don't know how useful the speed data will be, unless you have a sensor on the boat. GPS won't be of much value. You should be able to get a WOT RPM, though. That will give you an important data point.

Yeah, you have to do speed runs both directions and average them. Takes wind into account, too.

But the OB reaching design engine speed at WOT is the big one. Unless, of course, the OP never intends to run that fast, but then, what would be the point of having such a big engine?

[Jimmyt]

Unless, of course, the OP never intends to run that fast, but then, what would be the point of having such a big engine?

+1

[JeffJuneau]

Hi, Thanks to all for the helpful information on prop size for a 26M. Yes Russ, I am still interested if you have a chance to check your prop specifications. It does sound like we have nearly the same load/weight on our 26M. Also though, I get the message that there is really no substitute for a proper WOT test, even with the similarities between our similarly powered 26Ms. Yes Tom, your right that i should be able to sample different directions on a calm day at close to slack tide and get a pretty good idea of my water speed at WOT with my GPS. I'll do that this spring.

[NiceAft]

JeffJuneau started out the thread with an apology.

I apologize if I should be able to determine this from some table (that I haven't found yet), but thought the Mac community would probably have the right answer

Don't worry about it Jeff, as you can see, there are many here eager to help. That's why we are the friendliest boating forum on the World Wide Web.

Thank Russ for making it possible.

[Jimmyt]

Hi, Thanks to all for the helpful information on prop size for a 26M. Yes Russ, I am still interested if you have a chance to check your prop specifications. It does sound like we have nearly the same load/weight on our 26M. Also though, I get the message that there is really no substitute for a proper WOT test, even with the similarities between our similarly powered 26Ms. Yes Tom, your right that i should be able to sample different directions on a calm day at close to slack tide and get a pretty good idea of my water speed at WOT with my GPS. I'll do that this spring.

As I understand it, you do the WOT test vs redline to make sure you aren't over-propped - assuming you're going to run some at WOT. Running over-propped (overloaded) at WOT is hard on the powerhead.

Under-propping will get you out of the hole fast, but would allow you to over-rev if the motor is not rev-limited. Running above redline isn't good either.

The speed comparisons come into play when you are trying to dial in the perfect prop for your use. Of course, while you are changing pitch, diameter, and number of blades, and doing multiple speed runs, you always need to keep an eye on the WOT vs RPM performance point. If you try to dial it in, plan on several days of fooling around. And find some way to get access to a variety of props (unless you have a big pile of money to get rid of, and you enjoy collecting props).

Of course, Russ's prop will probably be plenty close. That's probably what I would do if I had that motor. I don't spend a lot of time at high speed, so I haven't fooled with mine, other than to check WOT vs RPM.

[JeffJuneau]

I just got back to checking the thread I started on the correct prop for my engine. Again, Thanks for all the help everyone. Your information makes sense jimmyt. My DF70A owners manual says that the "target full throttle operating range" for this engine is between 5000 and 6000 rpm. I don't know if "target full throttle operating range" is intended by Suzuki to be the same as Wide Open Throttle. I will, per your advice, keep it within that range during my testing this spring. And yes, I am guessing that Russ's prop will be a good proxy for what my Mac should have. I doubt the dealer has a bunch of props for me to test, so I will probably only buy a new prop if I am convinced by the testing that this is the sub-optimal prop for my situation.

[Jimmyt]

I just got back to checking the thread I started on the correct prop for my engine. Again, Thanks for all the help everyone. Your information makes sense jimmyt. My DF70A owners manual says that the "target full throttle operating range" for this engine is between 5000 and 6000 rpm. I don't know if "target full throttle operating range" is intended by Suzuki to be the same as Wide Open Throttle. I will, per your advice, keep it within that range during my testing this spring. And yes, I am guessing that Russ's prop will be a good proxy for what my Mac should have. I doubt the dealer has a bunch of props for me to test, so I will probably only buy a new prop if I am convinced by the testing that this is the sub-optimal prop for my situation.

Target full throttle operating range is the target you are shooting for. When you operate the engine/prop combo at WOT, it should fall within that range - when you get the correct prop.

Tell the dealer what you're doing. They may allow you to at least return undamaged props in exchange for the next one you try. If you damage one, I'd expect you'd own it though.

[Tomfoolery]

Run your OB at WOT in whatever configuration you will be using at full speed, like ballast out and mast up. Record the engine speed. Divide that by 6000 rpm to get some number less than 1, assuming the engine doesn't get to 6000 of course. Multiply your existing pitch by this number to get the desired pitch. Round up the pitch value to the nearest whole number. That should get you there, or pretty close, assuming the diameter remains the same.