Ribcraft 585 / Suzuki Df140 - 13” diameter prop OK?

[Pikey Dave]

Originally Posted by gpsguru

My 585 with the Mercury 150, propped with a REV4 14 5/8dia 19P I am cruising at the same speed but at 3600rpm.


The 150 has bags of torque and the WOT is 5000 - 5600, so 4000 rpm is a little over 30knts and 5000rpm is about 42knts, and the engine runs out of puff at 5300-5400 rpm which is a brown trouser 45knts ish ..... I don't go there very often as at that speed you need 1000% concentration and eyes like a hawk !

The 150 is a completely different beast to the 140. As you say, loads of torque and can take the Rev4 prop which the 140 can’t. The Rev4 is probably the best RIB prop I’ve come across and would be my first choice if it fitted the 140. The 140 is a tuned 90/115 & lacks the displacement for low down torque.

[scrambler]

Originally Posted by Pikey Dave

If those RPM figures are correct, which they shouldn’t be as the rev limiter should be cutting in at 6300, you’re well under propped. I’d like to see an engine printout to see the RPM profile.

The figures are correct, they're digital off the plotter which is linked to the Suzuki gauge. I'm just not certain if what I thought might be 6500 was in fact 6300. I double checked 6400 because I was surprised to see it. It was in red. Because of the chop the revs and speed were bouncing up and down very quickly.
Maybe your figure of 6300 relates to an older generation df140. Mine is a 2016 manufacture on a 2018 boat.
The prop is the standard 3 blade alu prop that Ribcraft fitted. I don't know its measurements. If you think Ribcraft are under propping their boats perhaps you'd better tell CC next time you speak to him and see what he says🤨. Performance is fine for my purposes, I never tow anything and I cruise economically at around .60/.65 litres per nm.

[cdbxyz]

Had a good run out today, paying more attention to rpm/knts.

There was a little tide running but I definitely think I’m a little under propped as I’m cruising 22-24knts at 4,500 rpm and comparing that to the Ribcraft sheet it saying 4.5k rpm should be 30knts.

Also really opened it up on a calm bit and was hitting 6200rpm with more to go on the throttle.

I’ve acquired a genuine Suzuki 3 x 13 7/8 x 21 stainless prop but I couldn’t get the right hardware bits to switch from the Michigan in time, will try that and update the thread once I have it fitted.

[cdbxyz]

Ok to round this out I fitted the Suzuki 13 3/8 x 21 SS yesterday and had a day out.

RPMs seem about 500 less for the same speed as the smaller prop, not quite as good as the Ribcraft document indicates rpm/knts but ‘shove’ through the rev range seems better and getting on the plane definitely feels a bit easier.

WOT we were seeing 6-6.1k rpm which is bang on for the engine and with 3 adults, 4 children, 150L of fuel yesterday we were seeing about 37/38 knts at slack water which is plenty enough. Expect we’d see more with less weight.

Definitely a worthwhile change!

[Pikey Dave]

Originally Posted by cdbxyz

Ok to round this out I fitted the Suzuki 13 3/8 x 21 SS yesterday and had a day out.

RPMs seem about 500 less for the same speed as the smaller prop, not quite as good as the Ribcraft document indicates rpm/knts but ‘shove’ through the rev range seems better and getting on the plane definitely feels a bit easier.

WOT we were seeing 6-6.1k rpm which is bang on for the engine and with 3 adults, 4 children, 150L of fuel yesterday we were seeing about 37/38 knts at slack water which is plenty enough. Expect we’d see more with less weight.

Definitely a worthwhile change!

Attachment 140522

All sounds good.[emoji106]

[AnthonyR]

Interesting… I too have just bought a 2015 RC585 Pro with Suzuki DF140A. It also came with a Michigan Apollo 3 x 13 x 21 stainless prop installed.

When I did the sea trial at the time of buying I noted that with 2 adults and about 50 litres of fuel on board, hole shot was a bit disappointing, but grip was excellent and it was very happy to rev. In fact, I was hitting the rev limiter really easily on WOT, boat speed circa 38/39 knots. For my purposes, this isn’t going to work however as the boat will generally only carry 2 at a time in general use and bouncing off the limiter isn’t great.

This leads me to believe that people are choosing the 3 x 13 x 21 stainless as an option if they are continually carrying heavy loads (100 litres fuel, 5 or 6 people) with this set up.

I am considering the aluminium 3 x 14 x 21 (I.e standard size) as I’d like to see the revs at WOT fall to 5,800 - 6,200 rpm and take advantage of better economy at cruising speeds, which the 13 inch prop can’t deliver. Whilst hopefully improving holseshot too.

Anyone have experience of trying lots of options with their setup? Enjoyed reading about the 13 7/8 x 21 stainless option which will perform pretty much as a 14 aluminium?

[beamishken]

Generally stainless props are usually more efficient than ally & usual advice is to reduce diameter/pitch to compensate when switching from a correct ally prop to stainless if you want the best out of the rig stainlessis the way forward. I'd suspect the ally prop your suggesting may bring your rpm down but without a corresponding increase in performance. You say hole shot wasnt great with your current prop which your thinking is slightly underpropped, If thats the case then when you improve your top end by increasing pitch/diameter then you will probably hurt your hole shot further. A good compromise may be to send your existing prop to a specialist & get it cupped which should help at the top end but not hurt at the bottom. Being slightly underpropped wont hurt your engine where going too far the other way can do damage, an engine held back by load is more likely to suffer harm & probably use more fuel than one happily running lightly loaded & reving free. Unless its severly overreving you may have the best prop for the boat. The only way to find out would be swap out your current prop for a larger pitch/diameter stainless & see if it can still make rated rpm, if it can't then you'll need to drop back to what you have. Speaking to an experienced prop specialist is probably your best option, someone who tunes props not just a salesman. Prop selection is a bit of a dark art & can get expensive if you buy the wrong thing hence a specialist is often the best option.

Sent from my SM-G950F using RIB Net mobile app

[cdbxyz]

To add a bit more of our experience following on from above - we ran the Suzuki 13 7/8 x 21 Stainless Steel I mention above for the whole summer, pulling a large sofa, cruising around and going for quick blasts, holeshot is good, top end is good without over revving and it was definitely better than the 13 x 21 Apollo which seemed too easy for the engine to rev and lacked torque.

As standard from RC I believe the 585 with DF140 comes with a 14 x 21 alu so the SS equivalent I have seems a very reasonable starting point.

I also believe from researching last spring, that the DF140 is geared to push a 14" diameter prop so again, seems like the best starting point and messing around with diameter isn't that smart.

All in all I think I could probably have saved some money and just got the standard pitched alu prop but the stainless one looks nice and it performs well for us

[AnthonyR]

Thanks for the update on your experiences with the 13 7/8 x 21 SS. It's kind of where my heart is at, but like you, I suspect the 14 x 21 alu would do largely the same job, but I too like shiny metal. Will go for one or other.

Your boat set up looks remarkably similar to mine (pic attached from when I did the sea trial in February. I've redacted the guys face who trialled it with me as he may prefer his anonymity).

I'm liking the look of the swim steps you have on yours. Are those a Ribcraft bolt on option?

Lastly... when you swapped out the Apollo prop for the Suzuki one (essentially I'll be doing the same thing), what hardware did you need to get to successfully install? Was it just the prop hardware kit (57630-90J00-000) that comprises spacer, washer, castle nut and pin, or did you need additional parts as well, like the stopper and propeller bush?

[cdbxyz]

The ladder is a batsystems setup which is usually only on when we are stationary, but it stays in place OK when on the move. My kids really wanted a ladder LOL

https://www.boatsystemgroup.com/en/b...6x35cm-5-steps

RE install kit - yes the part number above is exactly what you will need to fit the Suzuki item, plus some appropriate grease.

[AnthonyR]

To also round out my experiences. I bought the 3 x 13 7/8 x 21 Suzuki stainless prop and swapped out the smaller 3 x 13 x 21 Apollo.

Tested on The Solent last weekend, 2 of us on board with 90 litres of fuel. Sea state was between calm and up to 0.4m waves.

Differences:

Holeshot is improved, not night and day, but definitely better.

WOT, still achieving 6,200 rpm but didn't hit the limiter - 40 knots top speed (two way run), may do a little bit more with flat seas and fiddling with the trim some more.

Biggest improvement is cruising fuel consumption. At 4,500 rpm was achieving 25 knots, 0.75 nm/litre consumption (really pleased with that). Whereas before to obtain 25 knots the engine was turning in excess of 5,000 rpm and giving back a poorer consumption.

Covered 37nM and used 36 litres of fuel (according to the Suzuki digital gauge) from mixed use. So just under a litre per mile. Will double check that when I brim the tank next time out.

I suspect from my testing and data that the 3 x 14 x 21 aluminium prop is probably spot on (already alluded to by cdbxyz), although I'm tempted to try a 23 inch pitch of the same 13 7/8 diameter or a 4 blade prop.

Anyone running a 4 blade prop for the DF140A that they might recommend.

[cdbxyz]

That’s good that your experience of the Suzuki 3 x 13 7/8 x 21 SS is very similar to mine, glad it has been an improvement for you. I didn’t have my fuel flow meter figured out when running the Apollo so can’t comment if I’ve seen similar improvements, but I am getting very similar fuel consumption to your figures.

I am also tempted to try a 4 blade for a bit of low down torque and better launching/low speed planing when I’m towing a 3 person sofa tube.

I’m tempted to try this https://www.steeldevelopments.net/co...39627123785777 which is a reasonable (ish) price - well it is compared to the genuine Suzuki prop.

Thinking maybe 4 blade 19 pitch would give more bottom and middle range for less top end.

I could then stick that on when planning to tow the sofa, and keep the SS on when doing normal trips.

[Daibheid]

Just keep in mind with stainless props, if you hit something with an alloy prop you'll probably bust your prop, hit something with SS and you'll likely bust your gearbox.
Another consideration is if you're operating somewhere that needs a lot of gearchanges, the higher inertia of a SS prop is harder on clutches especially going from F to R etc so always good to pause in neutral where possible.